Future Communications Infrastructure - Step 2: Technology Assessment Results

Transcription

1 EUROCONTROL Future Communications Infrastructure - Step 2: Technology Assessment Results Edition Number : 1.0 Edition Date : 29/10/07 Status : Final

2 DOCUMENT CHARACTERISTICS TITLE Future Communications Infrastructure - Edition Number: 1.0 Edition Date: 29/10/07 Abstract This document describes the result of the assessment of candidate technologies as part of the joint EUROCONTROL/FAA Future Communication Study. It gives a brief outline of the activities undertaken during the study, the assessment methodology, common evaluation scenarios, the assessment of the technologies, and the final conclusions and recommendations. Future Communication Study Keywords FCI AP17 Datalink COCR Terrestrial systems Satellite systems Aeronautical communications IEEE e Requirements Spectrum AMSS/AM(R)S B-AMC AMACS P34 (TIA-902) ATM SATCOM SwitfBroadband Iridium NEXT Page ii Final Edition: 1.0

3 DOCUMENT CHANGE RECORD The following table records the complete history of the successive editions of the present document. EDITIO N NUMBE R EDITION DATE REASON FOR CHANGE PAGES AFFECTED 0.a May 2007 Initial draft with missing information All 0.b August c September 2007 Updated with ATM SATCOM B-AMC, and AMACS information Updated with revised information from B-AMC and AMACS 1.0 October 2007 Updated with comments All All All Edition Number: 1.0 Final Page iii

4 CONTENTS DOCUMENT CHARACTERISTICS... 2 DOCUMENT CHANGE RECORD... III ABBREVIATIONS... VII 1. INTRODUCTION Future Communication Study Action Plan Scope of this document Assessment Activities BRIEF TECHNOLOGY DESCRIPTIONS Introduction AMACS B-AMC WCDMA P34 (TIA-902) LDL Inmarsat SwiftBroadband New satellite systems (Commercial or custom ATS) IEEE e Assessment APPLICATION OF THE ASSESSMENT CRITERIA Overview Essential criteria Desirable Criteria Ranking FRS within the context of the Future Communications Infrastructure AMACS Page iv Final Edition Number: 1.0

5 4.1 Reference information Description Functional Architecture Essential Criteria B-AMC Reference information Overview Summary table LDL Reference information Description Desirable Criteria Performance Based Criteria PROJECT 34 (P34 (TIA-902)) Reference information Description Essential Criteria Desirable Criteria WCDMA Reference information Description Desirable Criteria Performance Based Criteria INMARSAT SWIFTBROADBAND Reference information Description NEW SATELLITE SYSTEMS Generic satellite communication components Edition Number: 1.0 Final Page v

6 10.2 ATM SATCOM Overview Iridium NEXT IEEE E Reference information Description Desirable Criteria Performance Based Criteria RANKING OF THE TECHNOLOGIES GENERAL CONCLUSIONS TECHNOLOGY ASSESSMENT CONCLUSIONS AND RECOMMENDATIONS Short listed technologies against frequency bands FRS within the context of the Future Communications Infrastructure OVERALL CONCLUSIONS APPENDIX A. - REFERENCE DOCUMENTS APPENDIX B. AMACS TECHNICAL DESCRIPTION APPENDIX C. B-AMC TECHNICAL DESCRIPTION APPENDIX D. WCDMA TECHNICAL DESCRIPTION APPENDIX E. PROJECT 34 TECHNICAL DESCRIPTION APPENDIX F. LDL TECHNICAL DESCRIPTION APPENDIX G. INMARSAT SWIFTBROADBAND TECHNICAL DESCRIPTION 127 APPENDIX H. ESA ATM SATCOM TECHNICAL DESCRIPTION APPENDIX I E TECHNICAL DESCRIPTION Page vi Final Edition Number: 1.0

7 3G 3GPP A/A AAC ACARS ACL ACM ACP AEEC AES A-EXEC A/G AIRSEP AMBE AMACS AMC AM(R)S AMS(R)S AOC AOR-E/W AP17 AP/S ARMAND ARP ASAS ASM ATC ATM ATM ATN ATS BER BGAN BOC B-AMC BSM BSS C&P ABBREVIATIONS Third Generation Third Generation Partnership Project Air/air Airline Administrative Control (Communication) Aircraft Communication And Reporting System ATC Clearances ATC Communications Management Aeronautical Communications Panel (ICAO) Airline Electrical Engineering Committee Airborne Earth Station Automatic Execution Service Air/ground Air-to-Air Self-Separation Service Advanced Multi-Band Excitation All purpose Multi-channel Aviation Communication System ATC Microphone Check Aeronautical Mobile (Route) Service Aeronautical Mobile Satellite (Route) Service Airline Operational Communications Atlantic Ocean Region East/West Action Plan 17 (FAA/EUROCONTROL) Airport Surface Arrival Manager Information Delivery Service Allocation/Relation Priority Airborne Separation Assurance System Any Source Multicast Air Traffic Control (Service) (Unit) Air Traffic Management Asynchronous Transfer Mode Aeronautical Telecommunications Network Air Traffic Services Bit error rate Broadband Global Area Network Business Operations Centre Broadband Aeronautical Multi-Carrier Communications System Broadband Satellite Multimedia Business Support Systems Crossing and Passing Edition Number: 1.0 Final Page vii

8 CCC CEPT CLNP CN C/I COCR COTRAC CoS CPDLC CTS CS D-ALERT D-ATIS DCL DCN D-FLUP DLL DOC D-ORIS D-RVR DSC D-SIG D-SIGMET DSNA D-TAXI DYNAV DVSI Eb/N0 ECAC EDGE EIRP emlpp FAA FANS FCI FCS FDD FDM FDMA Common Control Channel European Conference of Postal and Telecommunications Administrations Connection Less Network Protocol Core Network Carrier to interference Communications Operational Concepts and Requirements Common Trajectory Co-ordination Class of Service Controller/ Pilot Data Link Communications (Services) Clear to send Circuit Switched Data Link Alert Data Link ATIS Departure Clearance Data Communications Wide Area Network Data Link Flight Update Service Data Link Logon or Data Link Layer Designated Operational Coverage Data Link Operational En-Route Information Service Data Link Runway Visual Range Downstream Clearance Data Link Surface Information and Guidance Data Link Significant Meteorological Information Direction des Services de la Navigation Aérienne Data Link Taxi Clearance Delivery Dynamic Route Availability Digital Voice System Inc Energy per bit to noise power spectral density ratio European Civil Aviation Conference Enhanced Data rates for GSM Evolution Effective isotropic radiated power enhanced Multilevel Precedence and Pre-emption Federal Aviation Administration Future Air Navigation Systems (ICAO Concept) Future Communication Infrastructure Future Communication Study Frequency Division Duplex Frequency Division Multiplex Frequency Division Multiplex Access Page viii Final Edition Number: 1.0

9 FEC Forward Error Correction FFT Fast Fourier Transform FL Flight Level or Forward Link FLIPCY Flight Plan Consistency FLIPINT Flight Path Intent FPS Frequency Planning System FRS Future Radio System FSS Fixed Satellite Service GES Ground Earth Station GGSN Gateway GPRS Service/Support Node GMSC Gateway Mobile Switching Centre GNI Ground Network Interface GoS Guarantee of Service GPS Global Positioning System GPRS General Packet Radio Service GRM Global Resource Manager GSM Global System for Mobile communications GS Ground Station GSO Geostationary Orbit HF High Frequency HGA High Gain Antenna HLR Home Location Register I-4 Inmarsat 4 th generation satellite ICAO International Civil Aviation Organisation IDRP Inter domain routing protocol IETF Internet Engineering Task Force IGA Intermediate Gain Antenna IOR Indian Ocean Region IOT In-Orbit Testing IP Internet Protocol IPS Internet Protocol Suite ISDN Integrated Services Digital Network ITP In Trail Procedure ITU International Telecommunication Union LES Land Earth Station LFV Luftfartsverket LGA Low Gain Antenna LRM Local Resource Manager MAC Media Access Control Layer MC-CDMA Multi-carrier code division multiple access MES Master Earth Station Edition Number: 1.0 Final Page ix

10 MSC MoU MSNDCF MSS MT N/A NAS NCS NOC OFDM OFDMA OPC Mobile Switching Centre Memorandum of Understanding Mobile Sub network Dependant Convergence Function Mobile Satellite Service Mobile Terminal Not Available Network Address Server or Non Access Stratum Network Control Station Network Operations Centre Orthogonal Frequency-Division Multiplexing Orthogonal Frequency Division Multiple Access Operational Control P34 (TIA-902) Project 34 PAIRAPP PCS PDA PDN PHY PIAC PLMN PPD PoP PPPoE PS PSS PSTN QAM QPSK QoS RAB RABM RAN RAN RANAP RF RL RNC RRM RTCA RTS Paired Approach Personal Communications System Personal Digital Assistant Packet Data Network Physical (layer) Peak Instantaneous Aircraft Count Public Land Mobile Network Pilot Preferences Downlink Point of Presence Point-to-Point Protocol over Ethernet Packet Switched Packet Switched Service Public Switched Telephone Network Quadrature Amplitude Modulation Quadrature Phase Shift Keying Quality of Service Radio Access Bearer Radio Access Bearer Manager Radio Access Node Radio Access Network RAN Application Part Radio Frequency Reverse Link Radio Network Controller Radio Resource Management Radio Technical Commission for Aeronautics Request to send Page x Final Edition Number: 1.0

11 Rx S&M SAP SBB SARPs SAS SBS SCC SDU SGSN SID SIGMET SIM SMS SSM SSPA SV TDD TDM TDMA TE TIS-B TT&C Tx UAT UE UMTS URCO UT UTRA USIM VDL VHF VoIP VOLMET VPN WGW Receiver Sequencing and Merging System Access Parameters SwiftBroadband (Inmarsat) Standards and Recommended Practices (ICAO) Satellite Access Station Satellite Base Station Satellite Control Centre Satellite Data Unit Serving GPRS Support Node Standard Instrument Departure Significant Meteorological Information Subscriber Identity Module Short Messaging System Source Specific Multicast Solid State Power Amplifier Service Volume Time Division Duplex Time Division Multiplex Time Division Multiple Access Terminal Equipment Traffic Information Service Broadcast Telemetry Tracking & Control Transmitter Universal Access Transceiver User Equipment Universal Mobile Telecommunications Service Urgent Contact Service User Terminal Universal Terrestrial Radio Access Universal Subscriber Information Module VHF Digital Link Very High Frequency Voice over Internet Protocol Broadcast Weather Virtual Private Network Working Group of the Whole Edition Number: 1.0 Final Page xi

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13 1. INTRODUCTION 1.1 Future Communication Study Action Plan 17 EUROCONTROL and the FAA initiated a joint study under a Memorandum of Co-operation (MoC) through a dedicated Action Plan (AP 17) to identify potential future communications technologies to meet safety and regularity of flight communication requirements, i.e. those supporting Air Traffic Services (ATS) and safety-related Aeronautical Operational Control (AOC) communications. The AP17 work considered several technical tasks in addition to non-technical ones referred to as business tasks. The business tasks were essential to creating dynamics and maintain commitment. Overall, there were six technical tasks and three business tasks. Tasks specific to the future communications study (FCS) were undertaken in three technical themes addressing key activities relating to the identification of the most suitable technology candidates for the future communication infrastructure. These were: (1) development of requirements and operating concepts; (2) identification and assessment of technology alternatives; and (3) development of a future communications roadmap. The third technical theme was a high level task that illustrated the evolution of communications technologies in the European and US regions. Further details can be found in ref 14. The other two tasks were undertaken in two sets of activities related to assessing communication technology: 1. A study to identify future communication requirements. The results of this activity are contained in the Communication Operating Concept Requirements (COCR) document. 2. An assessment to identify the most appropriate new technologies for the Future Radio System (FRS) within an overall end-to-end Future Communications Infrastructure (FCI) to support the identified communication requirements. This report covers the second activity (Technical Task 3 of the AP17), that is, to investigate, assess and recommend communication technologies for the future communications infrastructure. Progress of the work has been regularly reported to the ICAO ACP/WGT (formerly WGC) and at the ACP/WGW to ensure a global consultation and to act on feedback provided. This report was produced by QinetiQ under contract to EUROCONTROL as part of the Future Air to Ground Communications Technology Investigation against Task Requirement Sheet 035/04 and amendments. 1.2 Scope of this document This document contains a brief overview of the various activities undertaken on assessing new technology. It concludes with the results of the assessment and recommendations regarding the new communications components needed within the context of the FCI in the timeframe of to provide data communication capability to provide expected operational concepts e.g. those emerging from SESAR. The FCI is illustrated in Figure 1-1 below. Edition Number: 1.0 Final Page 1

14 a/a coms Satellite System(s) VHF New Terrestrial System(s) VHF Figure 1-1 Future Communication Infrastructure - a potential scenario for Assessment Activities This section provides an overview of the assessment undertaken on a wide range of communication technology and the methodology adopted. The EUROCONTROL assessment was conducted by QinetiQ in Europe on behalf of EUROCONTROL and by ITT Industries in the US on behalf of FAA/NASA. In addition, European States (France, Germany, Spain, Sweden and the UK) supported the assessment process and contributed to the work through investigation of specific technologies or feedback on the results. In particular, DSNA (France) and LFV (Sweden) progressed the design and evaluation of AMACS, NATS (UK) contributed to the investigation of performance of P34 (TIA-902) and AMACS, and EUROCONTROL funded a study to investigate B-AMC. The European Space Agency (ESA) also provided information on a potential future satellite system Initial Technology Pre-screening Activity started with an initial technology pre-screening assessment of candidate systems for new components of the FCI. The aim of the pre-screening was to reduce a large number of potential systems to a few promising technologies and this was achieved through two independent study activities conducted in parallel in Europe and in the US by the assessment teams. Both studies used a commonly agreed initial set of assessment criteria and similar scoring methods. Details of the pre-screening assessment can be found in Ref 13. The full list of technologies from which a subset was assessed is shown in Table 1-1 below. The technologies were grouped into categories and representative examples from each were evaluated. Page 2 Final Edition Number: 1.0

15 Technology Family Cellular Technology Derivatives IEEE 802 Wireless Derivatives Public Safety and Specialized Mobile Radio Satellite and other Over Horizon Communication Custom Narrowband VHF Solutions Custom Broadband Military Other Candidates TDMA(IS-36), CDMA(IS-95A), CDMAone(IS-95B), CDMA2000 1xRTT, WCDMA(US)/UMTS FDD(Europe), TD-CDMA(US)/UMTS TDD (Europe), CMDA2000 3x, CMDA2000 1xEV, GSM/GRPS/EDGE, TD- SCDMA, DECT IEE , IEEE , IEEE , IEEE , ETSI HIPERPAN, ETSI HYPERLAN, ETSI HYPERMAN APCO P25 Phase 1, APCO P25 Phase 2 TETRA Release 1, TETRAPOL, IDRA, IDEN, EDACS, APCO P34, TETRA Release 2 (TAPS), TETRA Release 2 (TEDS), Project MESA. SDLS, Connexion by Boeing, SwiftBroadband (Aero B-GAN), Iridium, Global Star, Thuraya, Integrated Global Surveillance and Guidance System (IGSAGS), HF DataLink. VDL Mode 2, VDL Mode 3, VDL Mode 3 w/saic, VDL Mode E, VDL Mode 4, E-TDMA ADL, Flash-OFDM, UAT, Mode-S, B-VHF(MC-CDMA) Link 16, SINCGARS, EPLRS, HAVEQUICK, JTRS APC Phone(Airphone, AirCell, Skyway) Table 1-1: List of considered technologies at Initial Pre-screening The initial technology pre-screening assessment methodology followed a requirement driven approach. At the time, the communication requirements were not clearly identified as these were being defined in a set of parallel activities in the development of the COCR document which was at an early stage. It is important to note that the initial technology pre-screening evaluated the capability of the technologies to support all requirements including both voice and data requirements (both addressed and broadcast requirements and both air/ground and air/air requirements). The initial pre-screening assessment examined candidate technologies against the criteria that were grouped in four categories: The first category describes the communication capabilities of the technologies. The second category characterises the maturity. The third category deals with cost items and the forth category comprises all other criteria. Following the initial assessment, an additional assessment was undertaken focusing only on the data requirements. The rationale for the second assessment was to take into account further discussions in the aviation community which indicated a move towards a data-only solution at least initially. Consequently the assessment was re-run and new results were obtained. The conclusion was that there is little difference in the results from the initial assessment based on similar criteria. In consultation with stakeholders it was recognised that the approach used in the initial prescreening assessment, being based on evaluation criteria, was a good intellectual process that provided a structured methodology and a clear scoring comparison. However, it has also been pointed out that this approach was difficult to apply in an objective way for many of the identified criteria and therefore there may always be an element of subjectivity in the final results. Furthermore, such the analysis was sensitive to the weightings of the various criteria. The task of achieving consensus in the weightings values could be an equally difficult exercise, (i.e. the need to agree a precise metric and description of the applicability of the criteria). It was also recognised that continuing to use the identified criteria and the subsequent reevaluation could require several iterations in order to capture the evolving and maturing Edition Number: 1.0 Final Page 3

16 concept for future operations. Another perceived limitation in the approach was the difficulty to predict other important factors in implementation decisions, such as stakeholder commitment and general financial situation. Finally, it was been considered that the importance of the overall score for any single technology was not always clear, especially as the study was not necessarily looking for a single technology with the best performance, but for the most appropriate combination of technologies. Based on the above points it was to adopt a two-step approach for the final stage of the technology assessment Final Technology Assessment: The Two Step Process In the first step, the focus was on selecting the technologies using a subset of the initially considered criteria, for which their applicability could be more easily agreed. For this subset it was agreed to consider the separate COCR requirements for air/ground, air/air and broadcast services and establish a list of promising technologies. In the second step, additional considerations/investigations covering the concerns covered by the other initial selection criteria were applied to the selected technologies, aiming to produce a further short list and recommendations for implementation Step 1 In this step a re-assessment of technologies considered in the pre-screening assessment was undertaken focusing on providing information on the capabilities of the candidate technologies to meet a reduced set of criteria composed of capacity (throughput) and Quality of Service (QoS) (i.e. Continuity, Integrity and Availability). The assessment investigated the technologies considering two aspects. The first was the capability to support the different type of services such as a/g and a/a and broadcast and addressed. The second one was the capability to operate in various type of airspace such as high and low density, en-route, TMA etc. The requirements for the parameters forming the reduced set of criteria are extracted from the most current version of COCR available at the time. The technologies were then matched to the requirements in the different airspace. The conclusions to the Step 1 are summarised in Table 1-2 below in which the candidate technologies are shown against the proposed operating band and service volume. The full report in contained in Ref 2. Page 4 Final Edition Number: 1.0

17 BAND AIRSPACE TECHNOLOGY VHF band Airport/Surface, TMA, En-route B-VHF L Band TMA, En-route (x)dl3, ETDMA, B-VHF, WCDMA, P34(TIA-902) C Band Airport/Surface e L Band AMS(R )S TMA, En-route, Oceanic SwiftBroadband, New Satellite System(s) Table 1-2: Step1 Technologies and proposed/potential operating spectrum Step 2 The aim of Step 2 was to conduct further in-depth assessment of the Step 1 short listed technologies. It was aimed at determining how and where each technology could be applied, and how they would perform in a typical operational environment. From this information recommendations on the most suitable technology would then be derived. A methodology to assess the technologies was developed [Ref 3]. The aim of assessment methodology was to identify simplified criteria against which the suitability of candidate technology could be matched. The criteria were developed in consultation with Stakeholders and their comments were taken into account. In developing the methodology and associated criteria and associated ranking it was agreed that the process had to be transparent and understandable. This lead to a simple set of evaluation criteria. Two main types of criteria were identified essential and desirable as described below. Essential criteria were considered to be the most important for a technology to be acceptable and were designed to be go or no-go decision items. Two criteria fell into this category Compatibility in the target band, and Openness of standards Compatibility in the target band is used to determine if the proposed technology can coexist with users currently operating or planned to be implemented in the target band. The target bands being considered in the FCS are VHF Band [ ] MHz (upper end of the VOR band) for airport, TMA and en-route communication L-Band 960 to 1164 MHz for airport, TMA and en-route communication C-Band MHz for airport surface communication Acceptance of this criterion is against existing or planned ITU planning requirements using theoretical calculations, simulations or measurement [Ref 5]. Use of these bands for communications is subject to agreement at the World Radio Conference 2007 (WRC07). Edition Number: 1.0 Final Page 5

18 Openness of standards is designed to determine if sufficient information is available on the technical standards on a fair and equitable basis. Availability of sufficient technical details is necessary to determine the characteristics of the technology and carry out some independent evaluation and validation if necessary. This information should be made available through an appropriate ICAO body. If the technical standards are not open to aviation in any form then the technology is rejected. Desirable criteria were also identified are used to help rank the technologies in terms of their suitability to meet requirements in the required locations. Included in this category are performance requirements i.e. capacity, continuity, availability, integrity and latency. Other desirable criteria were considered and after much debate a limited number were chosen. These cover those attributes of potential technologies which are major discriminates in comparing one against the other. The following were chosen to be the most relevant Robustness of the RF signal Technology Readiness Level Flexibility Ground Infrastructure Cost The technologies have been evaluated against the above criteria and a ranking scheme has been applied to each technology. The ranking results in a number of technologies in each class and used to inform the technology recommendations. To enable comparative evaluations to take place, a family of generic operational scenarios were defined based on an extrapolation of real world ATC sectors and traffic loading from the SAAM tool which is expected to exist in the Phase 2 timeframe (~2025). The common set of evaluation scenarios [Ref 4] were developed to be used in all technologies assessments and from this identify the technologies which are best suited to the various operational scenarios. The following candidate technologies as shown in Table 1-3 were considered in Step 2 based on earlier down selection from the Step 1 process with some minor refinement noted below the Table. Page 6 Final Edition Number: 1.0

19 Terrestrial systems: long range AMACS B-AMC WCDMA P34 (TIA-902) LDL Airport surface systems: short range Satellite systems IEEE e Inmarsat SwiftBroadband New satellite system(s) (commercial and/or custom ATS) Table 1-3 : List of technologies for Step 2 assessment An evolution of the technologies took place following results of the assessment carried out in Step 1. The following changes took place AMACS is based on features identified in Step 1 and represents a merger of ETDMA and xdl4 concepts B-AMC is the new name for a B-VHF like system operating in the L-band identified in the Step 1 process LDL is the new name adopted for xdl3 which was identified as a candidate technology in the Step 1 assessment The remainder of this document provides a description of the technologies considered above, the results of the assessment and provides conclusions with recommendations. Edition Number: 1.0 Final Page 7

20 2. BRIEF TECHNOLOGY DESCRIPTIONS 2.1 Introduction This section provides a brief introduction to the communication technologies that were assessed as potential candidates for new components of the FCI. Sections 4 to 11 and associated Appendices contain more detailed information and an assessment of each technology. 2.2 AMACS AMACS (All purpose Multi-channel Aviation Communication System) has evolved from E- TDMA and xdl4 concepts to provide an adapted technical solution for the data-link communications needs of AMACS is a multipurpose communication system, with cellular narrowband ( khz),which is intended to operate in the MHz frequency allocation designed for flexible deployment. Its key design drivers are flexibility, scalability and robustness. AMACS supports all forms of communications services. More details can be found at Appendix B. 2.3 B-AMC The B-AMC (Broadband Aeronautical Multi-Carrier Communications System) is a cellular broadband system capable of supporting multiple applications for providing various kinds of ATS and AOC voice and data link services simultaneously. It is based on the previous project known as B-VHF and reuses many of its features. B-AMC has the ability to support air-ground party-line voice communications based on the feature inherited from B-VHF but this capability has not been considered as the primary requirement is for data communications. B-AMC is proposed to operate in the L-band. More details can be found at Appendix C. 2.4 WCDMA In the assessment of Wideband Code Division Multiple Access (WCDMA) the characteristics of Frequency Division Duplex have been used. This is based on separate 5 MHz bands for uplink and downlink, with approximately 100 users per cell on the forward and reverse links. For aviation purposes this would be operated in the L band. More details can be found at Appendix D. 2.5 P34 (TIA-902) P34 (TIA-902) refers to a specific set of standards (i.e. TIA-902) developed by TIA under the Project 34 activity. It defines is a wideband digital radio system designed to support public mobile radio services and offers the capability for approximately 100 kbps data rates in a 50 khz channel up to approximately 500 kbps in a 150 khz channel. A system based on P34 (TIA-902) is proposed to operate in the L-band. Page 8 Final Edition Number: 1.0

21 More details can be found at Appendix E. 2.6 LDL The L-Band Data Link technology is essentially the VDL Mode-3 technology specification band-shifted and with a re-designed physical layer for L-Band operation based on the UAT physical layer. LDL is proposed to operate in the L-band. More details can be found at Appendix F. 2.7 Inmarsat SwiftBroadband Inmarsat introduced a new aeronautical mobile communication satellite services called SwiftBroadband (SBB), supported by new Inmarsat 4 (I-4) satellites. SwiftBroadband is the aeronautical service offered as part of the generic Global Broadband Area Network (BGAN). SBB is initially aimed at passenger services and ATS services are not currently supported due to technical limitations in the current design of BGAN. These include lack of priority or pre-emption mechanisms for ATS and problems in aircraft antenna performance. Currently there are no plans to add these features to SBB to support ATS. In addition to the technical issues, there is currently no commitment by Inmarsat or its supply-chain partners to support SBB for ATS purposes. However the Aeronautical Mobile Satellite Service (AMSS) continues to be offered by Inmarsat based on the Classic Aero family of services and other satellite operators which are compliant with the ICAO SARPS. The AMSS supports ATS voice and low speed data communication in oceanic and remote regions of the world. More details can be found at Appendix G. 2.8 New satellite systems (Commercial or custom ATS) Although SBB mentioned above has some potential to support ATS in the medium term, the I-4 satellites will be reaching the end of their design life around 2020 therefore cannot be considered as a long term new component of the FCI. However there can be no doubt that satellite-based communication offers great benefits to aviation. Currently satellite-based communication technology is limited to oceanic or remote areas of the world. In the longer term there appears to be potential for satellite communications to be used in higher density airspace to complement terrestrial systems provided that the quality of service required for safety related services can be achieved. In the timeframe of new satellite-based communication technologies are expected to emerge which could be used for ATS and AOC communication. A range of options for satellite communication using low-, medium- and geostationary orbit satellites are expected to be available offering mobile communication services to aircraft. These could range from commercially operated systems offering a generic service to all mobile users (land, maritime and aviation) to system targeted to meet specific aviation requirements. Examples systems which have potential as future satellite systems have been identified in the study. Initial information is available but insufficient to support a detailed assessment. These examples are discussed below. Edition Number: 1.0 Final Page 9

22 2.8.1 ATM SATCOM The ESA ATM SATCOM system can be briefly described as a modernised version of the ICAO Classic Aero Satcom System (or AMSS) with the view of providing satcom service for ATM in all types of airspace i.e. including high density continental airspace and to all types of aircraft. ATM SATCOM reuses some concepts of the AMSS, such as use of geostationary satellites, while overcoming the legacy system limitations. The aim is to support future ATM mobile communication services with the required performance level by possibly complementing terrestrial communication systems. Under the umbrella of the Advanced Research in Telecommunication Systems (ARTES) Programme, ESA has initiated a dedicated programme called Iris to support the development and deployment of satellitebased safety-of-life Air/Ground communications. More details can be found at Appendix H Iridium NEXT Iridium LLC is embarking on the design of the next-generation of the Iridium satellite constellation. This new system currently known as Iridium NEXT is proposed to seamlessly replace satellites in the current constellation and will be backward compatible with present applications and equipment. It will provide new and enhanced capabilities with greater speed, and bandwidth which is expected to be available to aviation. 2.9 IEEE e is the IEEE developed standard for Wireless Metropolitan Area Networks (MAN). The standard was originally defined for fixed access only; however, mobility was added by publishing a corrigendum to the standard (known as e). It is proposed that e is deployed at airports for data link applications on the surface of the airport. There is already interest by aviation Stakeholders in performing trials at airports with e based systems. The system is proposed to operate in the C-band. More details can be found at Appendix I Assessment Details of the assessment of the technologies against the evaluation criteria are contained in sections 4 to 11 below. Page 10 Final Edition Number: 1.0

23 3. APPLICATION OF THE ASSESSMENT CRITERIA 3.1 Overview This section provides a description of the criteria against which the technologies have been assessed. In general the technologies were reviewed against the following criteria Essential criteria Compatibility in the target band Openness of standards Desirable criteria Robustness of the RF signal Technology Readiness Level Flexibility in deployment Ground infrastructure costs Performance These are discussed in more detail below. 3.2 Essential criteria Compatibility in the target radio band As the new communication system is being targeted for operation in existing aeronautical bands which are occupied, compatibility with the existing users is essential. The use of these bands is subject to WRC-07 approval of co-prime allocation to AM(R)S. The target bands being considered are VHF Band [ ] MHz (upper end of the VOR band) for airport, TMA and en-route communication L-Band 960 to 1164 MHz for airport, TMA and en-route communication. C-Band MHz for airport surface communication Note: To date no technology was proposed for deployment in the extension VHF band at this stage. In the long term the VHF band could be considered for deployment of a new system provided sufficient spectrum can be made available. Due to the propagation constraints of systems operating in the C-band (e.g. atmospheric effects) the L-band is considered the main option for deploying a new long-range communication system. Consequently the main areas of study have been interference measurements for the candidate technologies proposed for the L-band against the current systems operating in the band e.g. DME. Before any new communication systems can be allowed to share spectrum with DME, a compatibility analysis must be performed to assess potential degradation of DME system performance. Ref 5 contains a comprehensive collection of reference material regarding co-channel interference. 1 Figures in square brackets [xx] are dependent on the outcome of WRC-07. Edition Number: 1.0 Final Page 11

24 A review has been undertaken of the candidate technologies in the following interference scenarios Co-site onboard an aircraft Air-air Air-ground Ground-to-ground. Due to the difficulty in separating antenna sufficiently far apart on an aircraft, the co-site scenarios were the most demanding environments. The next most demanding scenario was the ground-to-ground one where an aircraft could be close to a radio transmitter. However in general this is less severe than the aircraft co-site scenario. Acceptance was based on demonstrating that agreed interference values such as desired-toundesired signals levels could be achieved. It is recognised that a complete interference analysis is a very complex and a time consuming process and was unlikely to be completed within the timeframe of the FCS. However sufficient evidence should have been provided to demonstrate compatibility at least theoretically but preferably through limited practical trials. If this criterion cannot be met then the technology is rejected Openness of the Standard This criterion is designed to determine if sufficient information is available on the technical standards on a fair and equitable basis. Availability of sufficient technical details is necessary to determine the characteristics of the technology and carry out some independent evaluation and validation if necessary. This information should be made available through an appropriate ICAO body. As a minimum, completion of the template shown in Appendix A to a reasonable level is required to pass this criterion. If standards exist but have a royalty payment associated with them or are subject to some form of limited usage, this could be acceptable. However has to be considered as an element of the implementation cost. If no standard currently exists then the system will be judged as passing provided that the entity progressing the system intends that the technical information will be made available in an open manner through an appropriate standardisation body including ICAO. The lack of standardisation activity could indicate lack of maturity of the technology, which will probably be reflected in the TRL level. It is also likely to increase the risk that the technology can be deployed within the relevant timeframe. Generally if the technical standards are not open to aviation in any form then the technology is rejected. However in the case of satellite systems which support multiple users, this is criterion is less strictly applied. Page 12 Final Edition Number: 1.0

25 3.3 Desirable Criteria Desirable criteria are those for which a range of possible values can be determined in various configurations. No one technology will meet or exceed all the requirements therefore assigning values to these criteria will assist in comparing candidate technologies against each other in a common way. The importance of each desirable criterion is assigned in the ranking process as described in section 3.4 below. The set of desirable criteria is split into two main categories general and performance based. The two categories are briefly introduced below Generic Criteria The general criteria cover those attributes of potential technologies which are major discriminates in comparing one against the other. Other criteria have been considered but the following were chosen to be the most relevant Robustness of the RF signal Technology Readiness Level Flexibility Ground Infrastructure Cost These criteria are described in more detail in section below Performance based Criteria Another set of key selection criteria is those associated with meeting the required capacity, integrity, availability and latency performance values. The performance values are defined in the Evaluation Scenarios document [Ref. 4] and have been determined for each of the following locations based on the requirements defined in the COCR [Ref. 1] namely: Airport Surface Airport Zone Terminal Manoeuvring Area En-Route Oceanic Remote and Polar For each of the locations, each technology will be evaluated as to its ability to meet the requirements. These criteria are described in more detail in section Generic Criteria Robustness of the RF signal This criterion is aimed at determining the robustness of the technology to interference of the RF signal. The FRS will have to exist in an environment where interference will come from existing users of the target band therefore the ability to handle a certain level of interference is vital. In addition interference can also be generated by other sources. For the evaluation this is defined as the intentional manipulation of the S/N ratio of a victim radio in such a way that it is no longer operational. Edition Number: 1.0 Final Page 13

26 The COCR defines the following security requirements for services which have high severe, high catastrophic or medium availability requirements which covers most of the ATS and AOC services - Requirement Id R.FRS- SEC.1a R.FRS- SEC.1b Requirement The FRS shall provide a measure of resistance against deliberate insertion of RF interference when providing services with high severe or high catastrophic availability ranking. The FRS should provide a measure of resistance against deliberate insertion of RF interference when providing services with medium availability ranking. Associated FCI Requirements R.FCI-SEC.1 R.FCI-SEC.1 The test for this criterion is dependent on the specific technology. A radio system using much more bandwidth than the bandwidth needed to transfer the information data rate is likely to be resistant to interference. Based on the above discussion, the following values for RF robustness were defined. Criterion Interference resistance level 1 Robust to interference greater than 15dB 2 Not completely robust to interference greater than 5dB 3 Low tolerability to interference 5dB or less Technology Readiness Level The TRL value assigned under this criterion is based on the current level of development of the technology as a whole i.e. the target FRS as to be deployed in the target band supporting the designated services. The standard definition of TRL level as shown in Figure 3-1 is to be used. It should be noted that typically there is a relationship between the TRL and the length of time to deploy a technology. The lower the TRL value the less mature the technology, the longer the development phase and consequently there is a greater the risk in achievable deployment by a certain date. The timescale envisaged for this criterion is By this time the FRS must have reached a high level of maturity i.e. TRL level 9 and then be deployed by 2015 to allow a period of pre-operational use before entering operational service in The TRL will be assigned based on the information supplied by the proponent of the technology on tests and evaluations undertaken to date in the development of their system. Page 14 Final Edition Number: 1.0

27 Figure 3-1 TRL stages For the technology evaluation the following grouping of TRL has been assigned. Criterion TRL number level 1 Technology is TRL 8 or 9 2 Technology is TRL 6 or 7 3 Technology is TRL 4 or 5 4 Technology is TRL 2 or 3 5 Technology is TRL 0 or 1 This criterion is important to gauge the maturity of the candidate technology. The TRL of a particular technology is highly correlated to its technical risk to be deployed within a given timeframe. A low value of TRL is likely to be high-risk and one would expect to see convincing evidence for how that risk was to be managed, including minimisation and mitigation strategy. In addition the lower the TRL level the longer until operational use. A system under development can progress more quickly to higher TRL levels depending on the amount of interest and investment to progress the technology through the development phases. In the aviation world, systems that have been deployed for safety related communications have taken between 8 (e.g. the AMSS) to 15 years (or longer) (e.g. Mode S) to come to maturity for operational use. This is illustrated in the simple figure below. Edition Number: 1.0 Final Page 15

28 15 Time before operational use (years) 10 Pessimistic 5 Optimistic Technology Readiness Level Figure 3-2 Illustrative figure of TRL against time to operational use In the case of the new components for the FCI, a target date of around 2020 is assumed. This date is just about achievable for TRL values of above 3 provided that activity to progress them starts immediately. For each technology a TRL value has been assigned. Although a generic description of the TRL levels were identified in Ref [3] these cannot be applied objectively. Consequently a refinement of the TRL levels specifically applicable to the FRS was developed. The description of the TRLs as applied the FRS is shown below in Table 3-1. Page 16 Final Edition Number: 1.0

29 TRL Step 2 TRL Description 9 FRS deployed at desired locations and is in operation supporting the designed aircraft population 8 Production FRS available for endto-end testing and demonstration at one or few sites including flight trials with several aircraft 7 Prototype FRS available for limited end-to-end testing at a chosen test site include limited flight tests 6 Technology demonstrator available operating in the correct band and using representative components for the final design in an end-to-end chain 5 Components of the FRS available for individual test in a representative Generic TRL definition Performance Level of integration Design Stability Reliability Sources of Evidence Actual technology system qualified through successful mission operations Actual technology system completed and qualified through test and demonstration Technology prototype demonstration in an operational environment Technology system/ subsystem model or prototype demonstration in a relevant environment Technology component and/or basic technology subsystem validation in relevant In-Service performance of technology is successful. Performance validated Performance of technology as part of the prototype meets the requirements Performance of technology gives high confidence that requirements can be met Lab performance demonstrates viability Final production design validated demonstrating internal and external integration. Fully integrated with prototype System interfaces qualified in an operational environment. Interfaces demonstrated at system level in a synthetic / high fidelity environment. Interfaces partially demonstrated at System/Subsystem level in a synthetic environment. Design stable subject to minor modifications Design baselined for full production phase. Technology design is baselined as part of the complete prototype Basic design of technology is stable with only minor changes Reliability is proven on final design Prototype demonstrat es reliability model. Reliability data indicates requiremen t is met In service reports. Acceptance trials. User feedback Trials reports, configuratio n audits. Integration trials / user feedback Field test reports Life Cycle stage In Service Manufacture Demonstrati on Demonstrati on Assessment Assessment Assessment Edition Number: 1.0 Final Page 17

30 TRL Step 2 TRL Description Generic TRL definition Performance Level of integration Design Stability Reliability Sources of Evidence environment. environment may be at a sub system level 4 Individual modules or layers of the FRS tested individually 3 Computer simulation or analysis of the elements of the FRS 2 Refinement of design into specific components 1 Paper design based on perceived key requirements Technology component and/or basic technology subsystem validation in laboratory environment Analytical and experimental critical function and/or characteristic proof-of concept Technology concept and/or application formulated Basic Principles observed and reported Lab testing requirements met Performance investigated through analytical experimentatio n and/or modelling. Performance predictions refined Performance predictions established. Impact on other systems is understood, specified and quantified e.g. on board tests of FRS with other systems Interface requirements specified and understood. The likely impact on interfaced systems are generally understood. Practical L-Band interference studies undertaken in laboratory Analytical assessment conducted to establish interface requirements. Theoretical L-Band interference studies undertaken Interface requirements understood at concept level only. Impact on other systems is understood at a concept level only. forecast. Initial technology design complete. Refinement of initial design based on analysis and experimentation Fluid Componen t reliability drivers understood. Predictions of reliability made Lab test reports Sub system Designs Component Designs Analytical Studies Published Research Life Cycle stage Assessment Assessment Concept Concept Concept Table 3-1 FRS TRL descriptions Page 18 Final Edition Number: 1.0

31 Flexibility This general criterion is aimed at identifying options in the deployment of a technology which could enable a range of data rates/bandwidth to be chosen to meet the requirements in a particular service volume or to be tailored to a specific radio band. For example, the technology could offer a number of data rates, modulation options and channel bandwidths which can be chosen to meet the requirements. More options in the technology provide better flexibility to deploy the technology to meet local requirements or constraints. Criterion Flexibility Value level 1 The technology can be deployed in several ways to provide a variety of performance values. 2 The technology can be deployed in only one way and provides fixed performance values Ground infrastructure costs This criterion is used to indicate the typical cost to deploy the ground element of the FRS technology within a region compared with a VHF system. Note - Avionic costs are not considered as they are not a discriminator between technologies at this stage of development. An estimate of the avionics costs of each technology will be similar due to this immaturity. All avionics are expected to be implemented in similar ways e.g. a new unit which will be required with its own antenna. This criterion is used to indicate the typical cost to deploy the ground element of the FRS technology within a region (e.g. ECAC or NAS). The cost will be based on the number of radio units needed to achieve coverage in the proposed service volume of the target system. It is recognised that a single technology may not be designed to achieve entire coverage in all service volumes. In this case the technology assessment will aggregate the costs of a combination of technologies to achieve entire coverage in the region. For example a technology may be aimed at airport surface coverage only. This would need to be augmented by an air/ground service technology and therefore its cost would be added. In determining the cost, the number of ground stations is derived from the technology deployment plan for each system. This cost is compared to that of an equivalent service offered by a VHF data radio system. The comparison will be done based on a regional implementation i.e. in ECAC airspace. Criterion Cost Value level times less than the cost of VHF ground data radio system 2 10 times less than the cost of VHF ground data radio system 3 Similar cost to VHF ground data radio system 4 10 times the cost of VHF ground data radio system times the cost of VHF ground data radio system Edition Number: 1.0 Final Page 19

32 A pragmatic approach was taken to applying this criterion by comparing the FRS system against the coverage achieved by current VHF RTF radio system. The simple approach of mapping overlapping cells across the designated coverage area at green field locations was considered to be too simplistic and not representative of how the FRS is likely to be deployed. It is expected that the FRS will be deployed at some or all existing legacy sites to minimise costs the time and cost of deploying new radio sites is time consuming and expensive. Consequently an approach was taken whereby a typical area was identified and the siting of current VHF radio sites examined to identify a typical siting plan. To compare the coverage achieved by current technology a typical deployment of VHF transmitters in a part of a large region in ECAC was determined. Figure 3-3 and Figure 3-4 below show the deployment of a radio sites to achieve TMA and en route coverage in typical large area. In the figures each site has given an arbitrary number as a site identifier. The number of sites and their placement has been determined based on a number of reasons The designated coverage volume to meet the operational requirement Use of existing sites to their maximum extent rather than the expensive alternative of a new green field site The maximum number of frequencies that can used at a single site which requires additional sites The environmental acceptability of the radio site at that location In the figures, the typical coverage volumes of the sites has been illustrated. It will be noticed that there is considerable overlapping coverage which is a combination of the need for redundant coverage and the limitation of number of frequencies that can be handled at one site. To support en-route and TMA communications a system operating in the L-band is preferred. The propagation characteristics are similar to VHF based systems and hence deployment of VHF sites represents a useful indication of deployment of an L-band system. For communications with aircraft operating in the en route airspace a minimum FL of 245 was assumed. For aircraft operating in TMA aircraft were assumed to operate around FL100. Based on these values, it was concluded that if the FRS could provide coverage of up to 200NM in an en-route environment the cost would be the same as the current. Lower ranges would require more sites and hence high cost. Similarly, for TMA a range of 107NM was chosen and again lower ranges would require more sites and hence high cost. It was assumed that each airport would continue to be covered by the same VHF sites as currently deployed, as at airports the line of sight requirement remains valid and is assumed in the COCR. It should be pointed out that there are a significant number of these sites so the number of airports being deployed mainly determines FCI infrastructure costs. Page 20 Final Edition Number: 1.0

33 Figure 3-3 Coverage of a typical set of VHF radio stations (200Nm FL350) Edition Number: 1.0 Final Page 21

34 Figure Coverage of a typical set of VHF radio stations (107NM FL100) Performance Based Criteria The performance of the candidate systems were evaluated against the requirements defined in the Evaluation Scenario document [Ref. 4] for each airspace location. Values used for this criterion range from 1 to 3. Value 1 means that the candidate technology as designed exceeds the requirements in the location for which it being assessed. A value 3 means that the technology does not meet the requirement in that particular location. A technology must meet requirements in one location from the following Airport Surface Airport Zone Terminal Manoeuvring Area En-Route Oceanic Remote and Polar Criterion level Capacity Integrity Availability Latency 1 exceeds 1,2 or 3 1,2 or 3 1,2 or 3 1,2 or 3 requirement 2 = meets 1,2 or 3 1,2 or 3 1,2 or 3 1,2 or 3 requirement 3 = does not meet requirement 1,2 or 3 1,2 or 3 1,2 or 3 1,2 or 3 Page 22 Final Edition Number: 1.0

35 In applying the criteria, for most technologies the performance information was subject to uncertainty so a value was not assigned. Instead a go or no-go approach was adopted indicated by a or a. 3.4 Ranking In order to rank technologies in terms of their suitability to meet requirements, a template was designed to capture criteria information. This enabled the technologies to be allocated a class Classes As a result of the information supplied in the criteria, technologies were grouped into one of 4 classes. The classes represent a measure of the suitability of the technologies to meet the requirement in that environment; the lower the number the more of the requirements can be met. Class 1 Proven, viable, standardised technology, available for operational use. Class 2 - Technology has potential to meet many requirements. Class 3 - Technology has potential to meet some requirements. Class 4 - Technology has potential to few requirements. Note - It is recognised that a technology that is ranked as Class 1 was not be identified as this means it meets the requirements to be the FRS and can be implemented now. This Class 1 template is included to show the complete set of classes Masks For each Class a mask is applied which determines which criteria level is considered. The masks for each Class are shown below and applied in section Error! Reference source not found.. The shading depicts the criteria values that are of interest in assigning the class to a technology Class 1 Mask Criterion Value Security TRL Flexibility Cost Capacity Integrity Availability Latency Class 2 Mask Criterion Value Security TRL Flexibility Cost Capacity Integrity Availability Latency Edition Number: 1.0 Final Page 23

36 Class 3 Mask Criterion Value Security TRL Flexibility Cost Capacity Integrity Availability Latency Class 4 Mask Criterion Value Security TRL Flexibility Cost Capacity Integrity Availability Latency 3.5 FRS within the context of the Future Communications Infrastructure EUROCONTROL commissioned a study to consider the Future Communications Infrastructure (FCI) in the timeframe [Ref 10]. Extracts of the findings of the study that are relevant to this study are described below. The study states that air/ground Communications Networks used as part of the Aeronautical Internet must fulfil four requirements: 1. Data Transfer using the Internet Protocol is supported. 2. A procedure is specified and implemented to allow a mobile node (i.e. an aircraft) to join the network, be assigned an IP Address on the network, and be notified of the IP Addresses of the Default Router and the network s DNS Server. 3. The operational and safety performance requirements for data transfer over the Air/Ground Network must be demonstrably met. These requirements derive from the Safety and Performance Requirements (SPR) for the Data Link Services in the applicable airspace. 4. The security requirements for Denial of Service prevention must also be met. That is, mechanisms must be in place to ensure that the availability requirement is met even when a deliberate attack takes place. It is also desirable that an air/ground network should provide a broadcast mode suitable for the support of multicast ground-to-air communications. This study is relevant to the final selection of the FRS as it will operate within an IP infrastructure. Further work on finalising the selection of the FRS should include verification that the required performance can be achieved on end-to-end basis within the FCI. This should Page 24 Final Edition Number: 1.0

37 include appropriate methods of assuring the required quality of service for safety related applications can be maintained across the entire communication system. Edition Number: 1.0 Final Page 25

38 4. AMACS 4.1 Reference information Ref 4-1 : Future Communications Infrastructure - Technology Investigations Description of AMACS Issue 1.0 (revised) 31/7/07 Ref 4-2 : AMACS Performance Analysis Helios 12/9/ Description As described in [Ref 4-1] AMACS (All purpose Multi-channel Aviation Communication System) is a multipurpose communication system, with cellular narrowband ( khz), operating in the MHz frequency allocation and designed for flexible deployment. Its key design drivers are flexibility, scalability and robustness. E-TDMA and xdl4 concepts have been merged to provide an adapted technical solution for the data-link communications needs of The AMACS concept is intended to provide a data-only service with significant requirements for QoS for air/ground point-to-point, air/air point to point and broadcast modes. Its flexible slot structure is adaptable to meet local requirements. It can support different channel bandwidths and bit rates to cope with the various operational needs and traffic densities foreseen in high-density areas of the world (e.g. Europe and North America) in the future. Its robust physical layer is based on the GSM/UAT modulation types associated with robust data coding for achieving the highest QoS in terms of latency. A multi-level QoS system is proposed to permit use of channel resources according to the QoS level required. Specific channel slots are reserved for high QoS transmissions. The efficient handling of QoS is based on the TDMA structured MAC layer and gives a guaranteed transmission delay. These communications can support the current ATN protocol or new ones based on IPv6. Common Signalling Channels (CSC), similar to those employed by VDL Mode 4, are proposed to maintain QoS levels during intervals of network degradation. Examples are the warm- and cold-start features if a ground station (or stations) should go off-line for any reason. CSCs would serve to broadcast new ground station frequencies to alert aircraft mobiles of the new channels to which they should tune. The AMACS frame length is designed for fast delivery of time-critical messages and has been set at 2 seconds, but can be adapted to a lower duration if necessary. 4.3 Functional Architecture A depiction of the AMACS functional architecture is shown in Figure 4-1. Page 26 Final Edition Number: 1.0

39 4.4 Essential Criteria Figure 4-1 Functional Architecture of AMACS Compatibility within the target band The AMACS system has been designed to be deployed in the lower L-band ( MHz) which already has an Aeronautical Radio-Navigation allocation. A new channel scheme will have to be provided in the band, to accommodate the AMACS system s use of channels ranging from 50 khz to 400 khz. One of the key problems for a future communication component that is intended to operate in the L-band ( MHz) is co-siting with other radio transmitters that also operate in the L-band. Even if a frequency separation is implemented, to provide some decoupling with other spurious emissions, the robustness of the new communication link will be drastically affected by the proximity of other transmitters on the same aircraft. Therefore the solution is to take advantage of Pulse Blanking Techniques that have been used in many other cases to reduce the effect of strong interference (which is the case on board aircraft due to the very small system isolation). Taking into account that two of the major interferers for the new communication system will be short pulsing transmitters (DME and SSR/Mode S), the duty cycle of the jamming pulses will be lower than that of the AMACS bit duration. The impact of the interference will therefore be limited to a few bits in the frame for which data coding will be the appropriate answer to mitigate the impact of the interference on the frame error rate. Such a pulse blanking mechanism has been defined in the UAT standards and will have a common bus interconnecting the avionics elements that could benefit from the information provided (pulse blanking signal whenever a transmitter is on). On the other hand the impact of AMACS onboard implementation on DME or SSR/Mode S will be limited by providing a frequency separation between the AMACS channel and the first DME receiving channel (i.e. 978 MHz) and by taking into account the small duty cycle of AMACS (0.15% in average on the basis of a 3ms usable slot duration). Edition Number: 1.0 Final Page 27

40 Power control option In order to reduce the level of interference for point-to-point, a power control option is possible. This can be done rather easily, using a small capacity in the signalling channels (afforded by the high capacity offered by the GMSK modulation option). It requires the ground base station to perform a continuous measurement of the received signals from each aircraft and then return this information to each aircraft. On reception of this information, the aircraft terminal uses it to feed a power control algorithm, which is an adaptive algorithm that converges to the optimum power, i.e. the power which is required for normal operations and acceptable BER. Advantage can be taken from algorithms developed for GSM Assessment level The results of the study on compatibility indicates that there are potential solutions to mitigate the most critical co-site interference scenario however there is insufficient evidence that AMACS is compatible with other users of its target band until further studies are undertaken. Therefore the results are inconclusive Openness of the Standard It is expected that the AMACS system will be developed in full consultation with stakeholders in an open manner. The detailed technical standards will be publicly available ultimately as an ICAO Manual Assessment level This criterion is passed Desirable Criteria Robustness of the RF signal AMACS has been designed to have good robustness at physical layer level to ensure both the highest QoS in terms of latency and predictive behaviour in a typical distorted propagation channel. The modulation scheme has some basic robustness characteristics that have been qualified with the GSM and the AMACS is based upon a double coding mechanism that could allow a gain of three orders of magnitude in corrected BER. It has a target level of C/I of 9dB. This has been assigned a criterion level of TRL Based on the information provided in [Ref 4-1] AMACS is considered to be at TRL 3 which equates to criterion level of Flexibility There are a number of design choices that have to be made to achieve a range of performance. It is not clear whether these are dynamically chosen or will be a final design choice. However given the number of options AMACS is considered to have good flexibility. Page 28 Final Edition Number: 1.0

41 This has been assigned a criterion level of Ground Infrastructure cost The AMACS system uses a concept of cells to provide coverage as apposed to the current VHF radio systems. It supports each operational scenario using spatial segmentation to take into account the typical message characteristics and requirements for different operational environment. Each cell can be geographically distinct and will have its own dedicated ground station operating on its own frequency. Cells are based on a geographical plan, which includes vertical segregation. Each aircraft shall have knowledge of the parameters of all the cells including the relevant ground station frequencies. A cellular scheme will provide the adequate configuration to the airspace controlled by ATC. The size of the cell can be tailored according to the traffic they support with their volume depending on: air traffic density deployed applications en-route, TMA, airport As a first assessment, three operational environments have been identified: En-Route Low Density cells, with a range of about the optical range 250NM (for lower airspace of the same type, smaller cells could be used taking into account the line of sight coverage limitations) En-Route High Density cells, with a maximal range of about 100 NM TMA cells, with a range of about 50NM modulated by the size of the airport Based on the need for deploying a pattern of cells and the limited range of the high density cells compared to current VHF systems it is considered considerably more sites will be required. The number is estimated to be more than double of current in high-density airspace. This has been assigned a criterion level of Performance Based Criteria Services supported Ref 4-1 states that AMACS has been designed to support the following specific communication types- air-to-ground point-to-point; ground-to-air point-to-point; air-to-air point-to-point; ground-to-air broadcast; Edition Number: 1.0 Final Page 29

42 air-to-air broadcast. This is summarised in the table below. Air/Ground Addressed Data Air/Air Addressed Data Function/Service Air/Ground Broadcast Data Air/Air Broadcast Data Table 4-1 Summary of AMACS communication services Ability to meet requirements Performance assessment of AMACS has been carried out using either 100kHz or 400 khz channels [Ref 4-2]. The results show that AMACS using a 400kHz channel can meet all the requirements for ATS communication in all airspace (APT, TMA, ENR and AOA) both throughput and latency. It is noted that AOC communications on the uplink experienced latency values slightly longer than required. Some optimisation of the uplink channels could resolve this issue. Consequently AMACS appears to meet the requirements of the COCR and Evaluation Scenarios using a 400kHz channel. Requirements in some airspace can be satisfied with 100kHz channels. The air/air communication mode has not yet been simulated and requires further work. Air/Ground Addressed Data Air/Air Addressed Data Air/Ground Broadcast Data Air/Air Broadcast Data Airport Surface Airport zone TMA, Enroute ORP AOA???????? Page 30 Final Edition Number: 1.0

43 4.4.5 Overall conclusion AMACS is at an early stage in development based on an aspirational goal of supporting all forms of ATS communication using a terrestrial infrastructure with capacity to meet AOC requirements as well. AMACS brings together a set of components used in the previously proposed ETDMA system, elements of VDL Mode 4 and GSM physical layer. Currently the design is at the conceptual stage but using proven components. However an integrated design has not yet been evaluated. The concept that the aircraft requires knowledge of its position and the frequency of operation to manage its log-on with the appropriate ground station is a technique which is novel and is an area that requires further investigation. There is insufficient evidence that AMACS is compatible with other users of the L-band. The results to date are inconclusive and further assessment needs to be undertaken. The performance of the AMACS protocols appears to support requirements in all airspace types. Overall there are features of AMACS which are attractive for the basis of a new system operating in the L-band. These include features that are tailored to ATS requirements, deterministic performance and reuse of commercial components Summary table The following figure summarises AMACs against the Class 4 template defined in the assessment methodology. The shaded cells indicate the results of the assessment. Spectrum Compatibility Open stds Criteri on Value Class 4 5 RF robustness TRL Flexibility Cost Capacit y Integrity Availability Latenc y Legend Achieved Inconclusive Failed Figure 4-2 Summary Class table for AMACS Edition Number: 1.0 Final Page 31

44 5. B-AMC 5.1 Reference information Ref 5-1: B-AMC System High Level Description Report D2.1 Issue /8/07 Ref 5-2: B-AMC Operating Concept and Deployment Scenarios Report D2.2 16/7/07 Ref 5-3: System Specification Including Standardization and Certification Considerations Report D3 Issue /8/07 Ref 5-4: B-AMC Interference Analysis and Spectrum Requirements Report D4 Issue /8/07 Ref 5-5: Expected B-AMC System Performance Report D5 Issue /8/07 Ref 5-6: B-AMC Aircraft Integration and Ground Infrastructure Report D6 Issue /8/ Overview The B-AMC system operates in the L-band and supports [Ref 5-1] two modes of operation- Air/ground (A/G) mode Air/air (A/A) mode The A/G mode assumes a star-topology where aircraft within a certain volume of space (the B-AMC cell) are connected to the controlling GS. Each GS provides multiple logical voice and data communications channels to its users by exploiting a dedicated broadband A/G channel. A/A communication between aircraft takes place in a decentralized, self-organized way on the so-called Common Control Channel (CCC), within communication bubbles defined by the radio range of involved B-AMC terminals. The GS is not required, but may be optionally deployed, with the functionality similar to that of an airborne terminal. The preferred B-AMC A/G sub-system deployment is as data-only system. Equipped users would receive B-AMC services via the B-AMC airborne radio operating in the A/G mode. The B-AMC GNI interfaces via ATN routers with external data link systems or directly with local data link servers operating in non-atn mode. In the future, dependent on the acceptance of an end-to-end IP concept, IP A/G routers may replace current ATN A/G routers Essential Criteria Compatibility within the target band B-AMC is designed to operate with the L-band with a variety of options for deploying its Common Control Channel, Forward Link, and Reverse Link within the band. The currently proposed (single) CCC allocation is at 968 MHz. These are depicted in Figure 5-1 below. Page 32 Final Edition Number: 1.0

45 2,6 MHz 500 khz 500 khz 500 khz FL RL CCC Note FL = Forward Link, RL = Reverse Link and CCC = Common Control Channel Figure 5-1 Possible options for introducing B-AMC in the L-band Interference studies were carried out under worst-case assumptions and not necessarily representative of a typical environment. The results indicate that it is theoretically possible to avoid causing interference to other users of the band DME, SSR and UAT by a combination of selecting B-AMC channels with a certain frequency offset from nearby DME systems, and ensuring that a minimum separation distance is maintained. This needs further work based on examination of the frequency planning requirements. The study considered was not able to determine whether it is technically feasible to implement B-AMC in the lower band of MHz but it may be suitable for A/A mode. This can only be determined by addressing a number of institutional issues. As expected the aircraft co-site environment where other L-band systems - DME, SSR and UAT - represented the most difficult interference scenario. It appears that interference cannot be resolved by the use of frequency and distance separation alone and use of the aircraft suppression bus would be necessary. This will affect those system connected to the bus if B- AMC has a high duty cycle. The study team identified a major problem with the inconsistency of input data and the lack of common metrics for interference investigations. It was recommended that comprehensive common assumptions be established and common interference evaluation criteria for all candidate L band technologies and the results of the calculations (or repeated calculations) be reviewed. In terms of spectrum requirements, the study identified that B-AMC required 7 x 500kHz channels in each direction which can be distributed throughout the L-band to meet the Edition Number: 1.0 Final Page 33

46 requirements based on a cellular cluster size of 7. This seems feasible as an in-lay system subject to spectrum planning Assessment level Although this criterion is an effectively 'go' or 'no go', there was insufficient evidence that B- AMC is compatible with other users of its target band until further studies are undertaken. Therefore the results are inconclusive and further assessment needs to be undertaken. Deployment within the L-band seems feasible as an in-lay system subject to spectrum planning Openness of the Standard It is expected that the B-AMC system will be developed in full consultation with stakeholders in an open manner. The detailed technical standards will be publicly available ultimately as an ICAO Manual Assessment level This criterion is passed Desirable Criteria Robustness of the RF signal B-AMC has been designed to have the appropriate robustness at physical layer level to meet the design BER. It has a target level of Eb/No of around 10dB. This has been assigned a criterion level of TRL Based on the considerable information provided in [Ref 5-1 to 5-6] the B-AMC design has reached a fairly advanced level of specification. Reuse of B-VHF elements, which were tested in laboratory conditions increase the level of maturity of the system. B-AMC is considered to be at TRL 4 which equates to criterion level of Flexibility There are a number of ways to deploy B-AMC and therefore it is considered to have flexibility. This has been assigned a criterion level of Ground Infrastructure cost Page 34 Final Edition Number: 1.0

47 As with B-VHF, B-AMC is expected to be deployed in a similar manner to current VHF ground stations. Consequently it is expected that the same number of B-AMC sites will be required as current VHF stations. This has been assigned a criterion level of Performance Based Criteria Services supported B-AMC has been designed to support the following types of service Air/Ground Addressed Data Air/Air Addressed Data Function/Service Air/Ground Broadcast Data Air/Air Broadcast Data Ability to meet requirements A comprehensive range of simulations have been undertaken during the study using the common evaluation criteria. The results of the simulations, using a Java model, show that B- AMC protocols can meet the requirements in all airspace types dependent on the coverage volume except the ENR Super Large service volume. This is not a design constraint as this volume is not representative of a typical deployment for a terrestrial system. In addition B- AMC as a terrestrial system is not able to offer communication the Oceanic/Remote/Polar volume. Airport Surface Airport zone TMA, Enroute ORP AOA Air/Ground Addressed Data Air/Air Addressed Data Air/Ground Broadcast Data Air/Air Broadcast Data Edition Number: 1.0 Final Page 35

48 5.2.5 Overall conclusion B- AMC draws on the experience of the B-VHF project which investigated and demonstrated the feasibility of a new multi-carrier based wideband communication system to support aeronautical communications. B-VHF carried out extensive laboratory trials using prototype equipment, which proved the concept. Many of the features of B-AMC are based on those used in B-VHF and therefore add confidence to the new work that has been carried. The theoretical design of B-AMC is well advanced and extensive studies have been undertaken on modelling interference effects to and from other users in the L-band and on performance simulation of the protocol under typical conditions. The initial results on compatibility in the L-band indicate that B-AMC, assuming worse case affects from systems operating in the band, indicate that it can be used as an in-lay technology between DME channels. In fact it may be possible to improve performance through additional measure such as interference-adjusted erasure decoding. The B-AMC protocol meets the all requirements (capacity and latency) identified in the Evaluation scenarios document except ENR Super Large. The performance may even be improvement by applying priority handling. It is considered that the design of the physical and link layers will meet the integrity requirements. Of the 3 options considered in the study it is recommended that Option 2 based on a frequency planning for B-AMC cells is utilised for air/ground communications. It was noted that if DME usage is reduced in the future, B-AMC could offer much more capacity (up to 1.4 Mb/s). For A/A mode communication Option 3 is the preferred solution i.e. unused non-dme spectrum at the low end of the L-band. If this option was used for a/g communication the full potential of B-AMC could be achieved (up to 1.4 Mb/s). Overall, the B-AMC design shows promise as a potential candidate component of the FCI subject to some further work. The includes establishing comprehensive common interference evaluation criteria for all candidate L-band technologies and review the results of the calculations included in the report based on such criteria Completing any design trade-offs to achieve required performance whilst achieving compatibility in the L-band e.g. including interference-adjusted erasure decoding and adding priority handling Investigation of handoffs Security measures such as encryption and authorization Definition of message formats 5.3 Summary table The following figure summarises the assessment of B-AMC against the Class 3 template defined in the assessment methodology. The shaded cells indicate the results of the assessment. Page 36 Final Edition Number: 1.0

49 Spectrum Compatib ility Open stds Criteri on Value Class RF robustness TRL Flexibilit y Cost Capacit y Integrity Availabilit y Latency Legend Table 5-1 Summary Class table for B-AMC Achieved Inconclusive Failed Edition Number: 1.0 Final Page 37

50 6. LDL 6.1 Reference information Ref 6-1: Identification of Technologies for Provision of Future Aeronautical Communications NASA ITT 21/7/ Description The L-Band Data Link technology candidate is essentially the VDL Mode-3 technology specification band-shifted and with a re-designed physical layer for L-Band operation based on the UAT physical layer. This technology is classified as part of the custom broadband technology family. This family includes a range of broadband technology specifications with potential applicability to aeronautical communications. A subset of these technologies, including LDL, is being specifically designed for aviation. While the proposed VDL3 technology was considered for implementation in a manner similar to the current aeronautical radio architecture (e.g. a host of radio through-out the NAS providing sector-based coverage), the proposed concept for LDL is the implementation of a regular grid of radio sites Essential Criteria Compatibility within the target band In common with all the other L-band compatibility studies initial results indicate that considerable on-board co-site interference is generated. However as with the other studies the interference conditions still required further work therefore the studies were not necessarily representative of the true conditions Assessment level This criterion is inconclusive Openness of the Standard It is expected that the LDL system would be developed in full consultation with stakeholders in an open manner. The detailed technical standards will be publicly available ultimately as an ICAO Manual Assessment level This criterion is passed. 6.3 Desirable Criteria Robustness of the RF signal Page 38 Final Edition Number: 1.0

51 A Carrier-to-Interference ratio of db has been assumed in the analysis. This has been assigned a criterion level of TRL Based on the information provided in [Ref 6-1] LDL is considered to be at TRL 4 which equates to criterion level of Flexibility The design chosen for LDL has several modes of operation based. This has been assigned a criterion level of Ground Infrastructure cost It can be assumed that LDL will be deployed in a similar manner to VDLM3 and is expected to be deployed in a similar manner to current VHF ground stations. Consequently it is expected that the same number of LDL sites will be required as current VHF stations. This has been assigned a criterion level of Performance Based Criteria Services supported LDL supports the following communications services. Air/Ground Addressed Data Air/Air Addressed Data Function/Service Air/Ground Broadcast Data Air/Air Broadcast Data Ability to meet requirements Initial evolution of the proposed LDL design indicates a throughput of between 37.5 to 100 kbps. These performance values can probably be improved with some optimisation of the physical and link layers. Based on the initial performance values the table summaries the potential airspace in which LDL could support communication. Edition Number: 1.0 Final Page 39

52 Air/Ground Addressed Data Air/Air Addressed Data Air/Ground Broadcast Data Air/Air Broadcast Data Airport Surface Airport zone TMA, Enroute ORP AOA?? Overall conclusion A number of options for design trade-offs for LDL have been undertaken and a theoretical design has been proposed. The design is at an early stage but the reuse of elements of VDLM3 could reduce the risk in developing the proposed system to maturity. However there are concerns over the throughput performance Summary table The following figure summarises LDL against the Class 4 template defined in the assessment methodology. The shaded cells indicate the results of the assessment. Spectrum Compatibility Open stds Criteri on Value Class 4 5 RF robustness TRL Flexibility Cost Capacit y Integrity Availability Latenc y Legend Achieved Inconclusive Failed Table 6-1 Summary Class table for LDL Page 40 Final Edition Number: 1.0

53 7. PROJECT 34 (P34 (TIA-902)) 7.1 Reference information Ref 7-1: Description and Analysis of P34 NATS (Helios) - ACP/1-IP/10 Ref 7-2: High Level Spectrum Compatibility Assessment for P34 - ACP/1-IP/11 Ref 7-3: Technology Assessment for the Future Aeronautical Communications System - NASA ITT May 2005 Ref 7-4: Identification of Technologies for Provision of Future Aeronautical Communications NASA ITT 21/7/06 Ref 7-5: P34 AND AMACS KEY CHARACTERISTICS AND PERFORMANCE COMPARISON Helios 28/9/ Description Project 34 (P34) is a set of activities to define a Public Safety digital radio system. The specific standard considered within the P34 activities is TIA-902 which defines a wideband that provides high-speed packet data services using variable size channels and was designed to operate in the 700 MHz band. It can support data transfer rates in 50, 100, and 150 khz channels. P34 (TIA-902) provides connectivity between mobile and fixed network, mobile to repeater to mobile, and direct radio to radio. It uses Time Division Multiple Access (TDMA) to share out the channel, and Orthogonal Frequency Division Multiplexing (OFDM) as the underlying modulation scheme, which uses a large number of closely spaced orthogonal sub-carriers to maximise the usage of the channel. P34 (TIA-902) has two different physical layers: Isotropic Orthogonal Transform Algorithm (IOTA), which is optional, and a Scalable Adaptive Modulation (SAM) layer, which is required. P34 (TIA-902) uses interleaving, scrambling, and forward error detection to protect the transmission against burst errors. There are several modes of communication: Radio to Radio; Radio to Fixed Network Entity (FNE) (i.e. ground station) Radio to repeater to radio; and Radio to vehicular repeater to FNE. The P34 (TIA-902) system is capable of providing point-to-point addressed and broadcast modes. This includes a direct mobile-mobile capability (without the need for a base station). This enables the technology to be considered for air-air communications in remote/polar regions. This technology needs to be adapted and transposed within an aviation-protected spectrum from the original band of 700MHz, which is specified in the original P34 (TIA-902) standard. Edition Number: 1.0 Final Page 41

54 7.3 Essential Criteria Compatibility within the target band Ref 7-2 contains the results of an initial study which considered deploying P34 (TIA-902) in a typical federated avionics infrastructure. To reduce the co-site interference would probably require the use of an onboard suppression bus. This allows aircraft L-band systems to either desensitize or blank their receiver, or delay their transmissions, whilst the transmitter of a peer L-band system is active. The minimum active period is an important design parameter and is currently specified for the suppression bus based on the compatibility between UAT and co-located SSR [ref. 4]. Although it is considered unlikely that the P34 (TIA-902) spectral footprint will raise the interference profile in the L-band considerably from the RF perspective, the overall compatibility will depend largely on the service usage profile. A thorough analysis of the time domain considering in detail the respective duty cycles of the victim and interfering systems is recommended before any overall conclusions can be drawn on P34 (TIA-902)s overall compatibility potential Assessment level The results of the study on compatibility indicates that there are potential solutions to mitigate the most critical co-site interference scenario however there is insufficient evidence that P34 (TIA-902) is compatible with other users of its target band until further studies are undertaken. Therefore the results are inconclusive Openness of the Standard Ref 7-4 contains a review of the patents granted against the range of standards for P34 (TIA- 902). The concept of use envisaged for P34 (TIA-902) means that some patents will not be applicable (for example IOTA physical layer). In addition some modifications that may be necessary to tailor the physical layer standard for the FRS results in bypassing of most physical layer patents. One patent that may be desirable for use in the FRS is a methodology proposed for power amplifier linearization, which influences definition of the MAC framing structure however this is not a major issue. In general most patents will expire before timeframe of deployment of the FRS and additionally the patents are not applicable to companies outside the U.S. Consequently intellectual property associated with P34 (TIA-902) is considered to have little or no impact on the FRS if it is an implementation based on this standard is pursued Assessment level This criterion is passed. Page 42 Final Edition Number: 1.0

55 7.4 Desirable Criteria Robustness of the RF signal Assumptions of required Eb/N0 of 14 db been used in the performance and interference calculations based on meeting the TIA-902 standards. No additional margin was assumed in the calculations therefore a criterion value of 2 has been assumed TRL P34 (TIA-902) as a technology is fairly mature for the target band and applications for which it was originally designed e.g. public safety applications. Trials have taken place in the band for which it was designed i.e. 700MHz. Although the use of P34 (TIA-902) for aviation purposes could benefit from the COTS development it will require modification to operate in a new band and may involve some modification of the physical layer. Consequently it is assessed at TRL 3 which equates to criterion value of Flexibility P34 (TIA-902) has three channels options which could be deployed in several ways to meet a range of performance values and therefore it is considered to have flexibility. However it is probable that there will be only one option to achieve the performance required for aviation purposes i.e. use of the 150kHz channel and consequently reduces flexibility. This has been assigned a criterion level of Ground Infrastructure cost The coverage volumes supported by P34 (TIA-902) are smaller (typically 100NM) than those supported by VHF technology therefore this has been assigned a criterion level of Performance Based Criteria P34 (TIA-902) can support the following communication services Services supported Technology Air/Ground Addressed Data Air/Air Addressed Data Function/Service Air/Ground Broadcast Data Air/Air Broadcast Data P34 (TIA-902) Ability to meet requirements In Ref 7-5 the results of simulations have shown that P34 (TIA-902) is capable of supporting requirements in for ATS and AOC services in small and medium en-route service volumes. This would require 100 khz of channel bandwidth for ATS and at least 300 khz of bandwidth to serve a combination of ATS and AOC requirements. Edition Number: 1.0 Final Page 43

56 The ability of P34 (TIA-902) to support requirements in other service volumes (e.g. Large enroute, TMAs, airport surface) have yet to be undertaken. Air/Ground Addressed Data Air/Air Addressed Data Air/Ground Broadcast Data Air/Air Broadcast Data Airport Surface Airport zone TMA, Enroute ORP AOA???????????? Overall conclusion The P34 (TIA-902) standards appear to have many features required for aviation safety communications and can meet the requirements for ATS and AOC at least in en-route airspace. P34 (TIA-902), assuming that the spectrum compatibility issues can be resolved, has the potential to be used as the basis for an aviation L-band system at lower risk through use of COTS standards Summary table The following figure summarises P34 (TIA-902) against the Class 4 template defined in the assessment methodology. The shaded cells indicate the results of the assessment. Spectrum Compatibility Open stds Criteri on Value Class 4 5 RF robustness TRL Flexibility Cost Capacit y Integrity Availability Latenc y Legend Achieved Inconclusive Failed Page 44 Final Edition Number: 1.0

57 8. WCDMA 8.1 Reference information Ref 8-1: Identification of Technologies for Provision of Future Aeronautical Communications NASA ITT 21/7/06 Ref 8-2 : EUROCONTROL CDMA Simulation Results (WP2, WP3), Roke Manor July 2006 Ref 8-3 : L-Band 3G Ground-Air Communication System Interference Study Roke Manor December Description The main WCMDA technology considered was UMTS. UMTS offers 3G voice and data bearer services, which provide the capability for information transfer mobile users and base stations. It is possible to negotiate and renegotiate the characteristics of a bearer service at session or connection establishment and during ongoing session or connection. Both connection-oriented and connectionless services are offered for Point-to-Point and Point-to- Multipoint communication. Bearer services have different QoS parameters depending upon maximum transfer delay, delay variation and bit error rates needed. 3G supports both dedicated as well as packet data services. As designed data rate ranges are flexible and range from <1 kbps up to 384kbps for R99. Packet data rates of up to 14 Mbps maximum are supported for High Speed Downlink Packet Access (HSDPA) (Release 5) and 5 Mbps for High Speed Uplink Packet Access (HSUPA) (Release 7). Modelling work was undertaken to determine the capacity of each technology solution, or more specifically to determine the minimum number of RF carriers (and therefore the amount of spectrum) required in L-band to provide ATC and AOC services to the predicted number and distribution of aircraft operating within European airspace in 2020 and It should also be noted that demonstration flights of a representative UMTS system operating in aeronautical bands were undertaken successfully in Error free data links were established at high Doppler speeds and data rates between 9.6 kbps up to 384 kbps were achieved. Flight trials were undertaken in clean spectrum in the VHF and C bands Essential Criteria Compatibility within the target band In the study [ref 8-2] it was concluded that the operation of the new UMTS air to ground communication link in the L-band may be possible if protection measures identified in the study are introduced. The issue of in-band interference into the co-sited airborne DME receivers remains a concern, as airborne UMTS transmissions operating in continuous mode can potentially desensitise the co-sited DME receiver front end. However, it is expected that this conclusion would apply to any continuously transmitting communication system operating in the band. UMTS standards also include compressed mode of operation (gating or DTX discontinuous transmission) which could be connected to the L band suppression bus. Though all compressed mode parameter are available no effort has been done so far to test co-sited DME compatibility under these conditions. Edition Number: 1.0 Final Page 45

58 Expressed in terms of spectrum, the minimum requirements were identified as 2 x 5 MHz carriers (one up and one downlink). Deployment of this WCDMA technology would require two cleared 5MHz bands in the lower and upper parts of the L-band. While 5MHz unused spectrum is available around 968 MHz, in the upper L band 1 TACAN (64X) is located around 1149MHz where the Uplink is supposed to be located. Although guard band requirements have never been studied it is possible that another 32 DME channels need to be reassigned in case 5 MHz spectrum needs to be cleared at either side of the UMTS Uplink. Due to the pressure in the DME band and the expected growth in Dames in Europe obtaining such cleared portions will be very difficult Assessment level The results of the study showed that there may be methods to mitigate the most critical aircraft co-site interference scenario e.g. through the aircraft suppress bus. However there was insufficient evidence that W-CDMA is compatible with other users of its target band until further studies are undertaken. Test results of co-site interference of DME onto UMTS have been made available. The study shows that a single DME can be located within UMTS s 5 MHz bandwidth but only at the outer skirts (left or right) of the spectrum bandwidth. As mentioned above the assumption that 2 x 5MHz of unused spectrum in the L-band would be available is unrealistic as there are plans to increase the number of DMEs in Europe in the future. Consequently, based on the available information the assessment level is failed Openness of the Standard Standards for WCDMA 3GG are widely available and can be freely downloaded from Assessment level This criterion is passed. 8.3 Desirable Criteria Robustness of the RF signal The required Eb/No ratio is 4.7 db. CDMA signals have an associated spreading gain and should therefore be considered more robust against interference compared to non-spread signals. In addition to this several db gain are achieved by using convolutional and turbo FECs. No additional link margin has been proposed in the assumptions therefore this has been assigned a criterion of TRL Although UMTS is widely deployed in its target band for its original application it will require modification for deployment in the L-band (move operating frequency, delete all 3G security Page 46 Final Edition Number: 1.0

59 implementations and rely on end to end security) Therefore the TRL value is estimated as 5 which is criterion value of Flexibility As a result of the simulations which were based on the establishment of dedicated links and taking into account the foreseen COCR data load a packet data system is proposed as a deployment scenario. UMTS is probably the most flexible technology because it makes use of adaptive multi-rate matching on top of variable spreading factor in the puncturing/repetition of the encoded data. Furthermore a whole series of frame structures is supported. A mobile user can x/rx simultaneously more than 3 different data streams having identical and/or different rates and QoS levels on dedicated or packet data links. Therefore the criterion value of 1 is given Ground Infrastructure cost The WCDMA (UMTS 3G) implementation considered will require a comprehensive 3G-type infrastructure and a cellular deployment with cell diameters of 160 NMs for enroute and smaller cells for airport and TMA coverage. Ground infrastructure cost is considered high when taking into account all 3G security measures (such as data encryption, authentication and use of SIM cards) as well as access to a switched network for voice operation. When going for a full IP implementation on packet data the number of base stations needed is very close to the amount of airports handling revenue flights. WCDMA is expected to be deployed in a similar manner to current VHF ground stations. Consequently it is expected that the same number of WCDMA sites will be required as current VHF stations. This has been assigned a criterion level of Performance Based Criteria Services supported WCDMA (UMTS 3G) can support the following communication services. Air/Ground Addressed Data Air/Air Addressed Data Function/Service Air/Ground Broadcast Data Air/Air Broadcast Data Ability to meet requirements The performance assessment undertaken was based on an early version of the COCR. The values for capacity assessment were based on a propriety simulation model which reinterpreted the COCR requirements resulting in a need of an average data rate throughput of Edition Number: 1.0 Final Page 47

60 1k bps per aircraft with peak data rates of 9.6 kbps in order to achieve the latency requirements. All simulations took place considering dedicated datalinks between aircraft and ground station based on Release 99 only (in line with the 2002 flight trials). In order to obtain objective spectrum need requirements all simulations included interference from 1 st, 2 nd and 3rd cell rings around the investigated cell. A summary of the results were - In the forward direction a single UMTS channel (2x5MHz) provides adequate capacity for the worst-case minute according to the SAAM data for 2020 and 2025, in both London and Switzerland. In the reverse direction, a single UMTS channel (2x5 MHz) provides adequate capacity for the worst-case minute according to the SAAM data for 2020 and 2025, in both London and Switzerland. The simulation also shows that a packet data link is preferred instead of establishing dedicated data links between ground and each aircraft individually although this was not tested. Airport Surface Airport zone TMA, Enroute ORP AOA Air/Ground Addressed Data Air/Air Addressed Data Air/Ground Broadcast Data Air/Air Broadcast Data?????? Overall conclusion WCDMA technologies are becoming widespread in commercial services and are the basis for 3G mobile phones, etc. They have inherent benefits in terms of efficient use of spectrum and cellular capacity. However it seems that compatibility within the target band the L-band will mean these advantages will not be able to be realised by aviation. In order to estimate the amount of guard band needed between a WCDMA system and DMEs and hence the amount of DME to be reallocated, compressed mode operation and co-site interference studies have to be performed. In addition for introduction into the L-band, WCDMA will require at 2 x 5MHz clear spectrum within the band. Obtaining this amount of spectrum in an already crowded band in Europe will be difficult if not impossible. Therefore based on available information, introduction of WCDMA in the L-band is not feasible and this technology is not recommended for further consideration. Page 48 Final Edition Number: 1.0

61 8.4.4 Summary table The following figure summarises WCDMA against the Class 4 template defined in the assessment methodology. The shaded cells indicate the results of the assessment. Spectrum Compatibility Open stds Criteri on Value Class 4 5 RF robustness TRL Flexibility Cost Capacit y Integrity Availability Latenc y Legend Achieved Inconclusive Failed Table 8-1 Summary Class table for WCDMA Edition Number: 1.0 Final Page 49

62 9. INMARSAT SWIFTBROADBAND 9.1 Reference information Ref 9-1 : SwiftBroadband Capabilities to Support Aeronautical Safety Services - Technical Description and application to ATS, EUROCONTROL May 2006 Ref 9-2 : Compatibility and co-existence of Classic Aero AMS(R )S and Iridium in the same airspace Inmarsat paper ACP/1-WP/22 May Description SwiftBroadband is currently aimed at non-safety services on aircraft e.g. passenger applications. It has potential to be used for safety services however some technical modifications to the system are likely to be necessary such as the inclusion of priority and pre-emption protocols. A full description of SBB is given in Ref 9-1. SwiftBroadband is currently only supported via the Inmarsat-4 (I4) generation of satellites, 2 of which have been launched. As the lifetime of the satellites is around 15 years, they will be nearing the end of their life around 2020 and therefore will need to be replaced early in Phase 2 defined in the COCR. However SwiftBroadband offers potential service during Phase 1 and the transition to Phase 2. Future generations of the Inmarsat family of satellites are likely to be backward compatible with SwiftBroadband and will draw on the experience of the service Essential Criteria Compatibility within the target band The Inmarsat I-4 satellite which supports SBB operates in the Mobile Satellite Service (MSS) L-band in the ranges MHz (satellite-to-mes) paired with MHz (MES-to-satellite). Compatibility within the L-band is achieved through adoption of common standards i.e. AMSS and careful spectrum sharing arrangements. This has enabled several service providers to offer AMSS in the band e.g. Inmarsat and MTSAT. This includes compatibility with SBB. Recently, as noted in Ref 9-2, interference from the Iridium system which operates in the band 1616 to MHz has been noted. There is no guard band between the Classic Aero transmitting band and the Iridium receive band. It is noted that the top 0.5MHz of the Iridium band is only used in the receive-to-aircraft direction. Since there is minimal separation between the frequency bands of the two systems, normal RF techniques to minimise emissions such as filtering are ineffectual. Consequently there is further work to ensure compatibility between SBB and adjacent MSS bands. Page 50 Final Edition Number: 1.0

63 Assessment level Based on the need for further work criteria is inconclusive Openness of the Standard SBB is based on propriety standards which have limited availability and are not in the public domain. If SBB were to be offered for ATS application additional information will need to be made available for inclusion in an ICAO Manual Assessment level Although information is not currently the case, if SBB were proposed to support ATS applications it is assumed that some more technical information will be made available therefore this criterion is passed Desirable Criteria Robustness of the RF signal In common with all geostationary satellite system the link margin is critical to both the performance of the communication service as well as economic viability. No information is available regarding the design choices the SBB link budget however it is assumed that minimal additional margin over the normal design goals. Ref 9-1 indicates that additional design changes are necessary to overcome signal fades during aircraft manoeuvres. This has been assigned a criterion level of TRL The SBB is currently entering service, operates in an aeronautical band and has been flown on some aircraft for passenger applications. However for ATS applications it is considered to have a TRL level of 7 due to the additional modifications required as identified in Ref 9-1 (e.g. technical changes to support priority and pre-emption for ATS messages). This has been assigned a criterion level of Flexibility As described in Ref 9-1 SBB can be deployed in a number of different configurations mainly based on the gain of the aircraft antenna i.e. classes of terminal. These large from high gain, high data rate versions (up to 432kbps) to low gain with around 50kbps. This has been assigned a criterion level of 1. Edition Number: 1.0 Final Page 51

64 Ground Infrastructure cost As SBB uses a geostationary satellite, the communication service offered from the satellite is very large approximately 1/3 of the earths surface. Consequently much of the ECAC area could be covered by one global beam or a set of spot beams as depicted in Ref 9-1. Comparison of the SBB coverage with the equivalent number of VHF ground stations is a very difficult comparison with the information currently available consequently this criterion is not assigned Performance Based Criteria Services supported SBB has been designed to support the following specific communication types- air/ground point-to-point; ground-to-air broadcast; This is summarised in the table below. Technology Air/Ground Addressed Data Air/Air Addressed Data Function/Service Air/Ground Broadcast Data Air/Air Broadcast Data SBB X Ability to meet requirements As indicated in Ref 9-1 the performance of SBB has yet to be confirmed in an operational environment. Information will become available when further implementations of SBB on aircraft occur over the next year or so. From initial considerations given in Ref 9-1 SBB appears to be able to meet requirements in the oceanic/remote areas and could have some potential in higher density airspace to be confirmed. Page 52 Final Edition Number: 1.0

65 Airport Surface Airport zone TMA, Enroute ORP AOA Air/Ground Addressed Data Air/Air Addressed Data Air/Ground Broadcast Data Air/Air Broadcast Data?? Overall conclusion The aeronautical offering via the Inmarsat SwiftBroadband service will provide a large data and voice service that is initially aimed at passenger services e.g. Internet in the sky. SBB is available in parallel to the Classic Aero service. Arrangements for access and use of the classic service will be unaffected by SwiftBroadband. The existing ATS infrastructure is currently heavily based on VHF technologies supporting voice and data communications. Introducing a VoIP based service, as supported by SwiftBroadband, is likely to have effects on the operational procedures e.g. how calls are established, the time taken to establish a call, the end-to-end transit time. This may not be an issue in lower density ECAC airspace or in the oceanic environment. The performance of the SwiftBroadband service can only be estimated based on limited simulation and laboratory testing. The actual performance will only be fully known when avionics are deployed and flown. A number of technical enhancements must be made to the SwiftBroadband service to improve performance for ATS applications such as priority and pre-emption. The minimum data capability of the SwiftBroadband terminals utilising low gain antennas, should they be become commercially available, would seem to meet the ATS requirements up to 2020 based on the results of the COCR (Phase 1) for all types of airspace on a service volume basis. Larger aircraft will have the full SwiftBroadband capability, i.e. high gain antenna systems providing up to 432kb/s. However it is yet to be confirmed that the continuity, integrity, and availability parameters can be achieved. Given that AOC requirements appear to be increasing during the life of SwiftBroadband and they appear to have lower quality of service requirements than ATS, it can be contemplated that AOC could be moved to SwiftBroadband thus freeing resources for ATS communications. Edition Number: 1.0 Final Page 53

66 9.2.6 Summary table The following figure summarises SBB against the Class 2 template defined in the assessment methodology. The shaded cells indicate the results of the assessment. Spectrum Compatibility Open stds Criteri on Value 1 RF robustness TRL Flexibility Cost Capacit y 2? 3 4 Class 2 5 Integrity Availability Latenc y Legend Achieved Inconclusive Failed The above table provides the results of the evaluation which indicate that SBB seems to be potential candidate. However, SBB is not offered for use as a safety-related communication system and will require modifications to achieve the required performance. In addition, in the timeframe of the FCI, the satellites supporting SBB will be reaching the end of their life. Based on these additional considerations, SBB is not recommended for consideration as a component of the FCI. Page 54 Final Edition Number: 1.0

67 10. NEW SATELLITE SYSTEMS 10.1 Generic satellite communication components In the timeframe of new satellite-based communication technologies are expected to emerge which can be used for ATS and AOC communications. A range of options for satellite communication using low-, medium- and geostationary orbit satellites are expected to be available offering mobile communication services to aircraft. These could range from commercially operated systems offering a generic service to all mobile users (land, maritime and aviation) to system targeted to meet specific aviation requirements. Systems which have potential as these future satellite systems have been identified already. Initial information is available but insufficient to support a detailed assessment. These are discussed below ATM SATCOM Overview Reference information Ref 10-1 : Technical Note - ESA-CNES contribution to FCI technology evaluation July 2007 The ESA ATM SATCOM system has been designed with the view of providing satcom service for ATM in all types of airspace i.e. including high density continental airspace and to all types of aircraft. It can be perceived as a modernised version of the ICAO Classic Aero Satcom System (or AMSS), which has been now in operation for more than 15 years. The ATM SATCOM solution reuses some concepts of the AMSS, such as reliance on geostationary satellites, while overcoming the legacy system limitations with the aim to support future ATM mobile communication services in all airspaces with the required performance level. In a similar manner to the existing AMSS, ATM SATCOM is characterised by: Interoperable Standard supporting Multiple Service provider scheme, Operation in protected radio-spectrum allocation for safety and regularity of flight i.e. ITU AMS(R)S allocation in L-band Geostationary Satellite Communication system, Ground to Air connectivity supporting ATM services. In addition, ATM SATCOM can be realised using lighter airborne equipment than that for the AMSS, whilst providing a more reliable service, and a better usage of available spectrum. Improved performance results from the integration of state-of-the-art satellite communication technology into the new system providing: Improved Quality of Service : better availability through satellite diversity and higher integrity Edition Number: 1.0 Final Page 55

68 Implementation of QoS processing, Lighter airborne terminals : minimal antenna size and drag, reduced transceiver size and weight, A formal assessment on ATM SATCOM has not been carried out however consideration has been given to the two essential criteria below Essential Criteria Compatibility within the target band ATM SATCOM is intended to be operated in the Mobile Satellite Service L-band and specifically within the AMS(R)S allocation. Compatibility with existing users of the AMS(R)S will need to be demonstrated and measures must be taken to ensure that adequate spectrum is available in the AMS(R)S band to support service provision. Based on the current information available this criterion is passed subject to the issues noted above Openness of the Standard The intention is that the standards for ATM SATCOM will be in the public domain. Based on the current information available this criterion would be passed Iridium NEXT Reference information Ref 10-2: Iridium NEXT The Next Generation Iridium Satellite Communications ICNS Conference May 2007 The existing Iridium satellite service, using a constellation of 66 LEO satellites, can provide an AMS(R)S service using standard Iridium telephony and data protocols. AMS(R)S coverage extends over 100% of the Earth surface using AES equipment specially equipped and provisioned for AMS(R)S operation. Non-safety AMSS service is also provided throughout the coverage area. The primary AMS(R)S services include circuit-mode voice for cockpit crew and packet-data emulation. The satellites in the current constellation will be replaced over the next 5 to 10 years with ones that have greater capability current named Iridium NEXT. This will enable a new generation of user equipment to be developed and deployed whilst maintaining backward compatibility. Figure 10-1 illustrates the planned capabilities for the new satellite service. Page 56 Final Edition Number: 1.0

69 Figure 10-1 Proposed Iridium NEXT capabilities Iridium sees aviation as an important market. The next generation satellite replacement program that will extend the value of Iridium to new, more robust aviation services. It will continue to serve polar and ocean routes but potentially even as back-up for low density terrestrial areas. Iridium NEXT is currently reviewing requirements and aviation is being invited to contribute to this process. A formal assessment on Iridium NEXT has not been carried out however consideration has been given to the two essential criteria below Essential Criteria Compatibility within the target band Iridium NEXT is expected to operate in the same band as the current Iridium i.e. Mobile Satellite Service L-band and specifically within the AMS(R) S allocation Openness of the Standard It is not known whether the Iridium NEXT standard will be developed in an open manner. Edition Number: 1.0 Final Page 57

70 11. IEEE E 11.1 Reference information Ref 11-1 : IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems Feb 2006 Ref 11-2 : Wireless Channel Characterization in the 5 GHz Microwave Landing System Extension Band for Airport Surface Areas NASA May Description IEEE is the IEEE developed standard for Wireless Metropolitan Area Networks (MAN). The standard was originally defined for fixed access only; however, mobility was added by publishing a corrigendum to the standard [Ref 11-1] (known as e). Some of the advantages of are that it: Provides very efficient use of spectrum Provides high bandwidth, with hundreds of users per channel Supports a wide range of applicable frequencies (up to 66 GHz) Provides high data rates for uplink and downlink Supports multiple physical interfaces It is proposed that e is deployed at airports for data link applications on the surface of the airport. The system is proposed to operate in the C-band Essential Criteria Compatibility within the target band The frequencies allocated for WiMax span the 2-66 GHz range. The exact frequency of operation for any given system is dependent on the propagation conditions that are encountered during its use. The frequencies higher than 10 GHz are practical only for fixed line-of-sight (LOS) type services. Non-line of sight (NLOS) communications perform better when the frequencies of operation are kept under 10 GHz. IEEE technology can be customised to free spectrum space within the MLS C Band for airport surface communications. The use of the C-band enables this under utilised resource to meet the demanding communication requirements on the surface of an airport as identified in the COCR and also for protection of the band for aviation use. Use of this band is important because - GPS navigation and WAAS/LAAS enhancements are circumventing the need for MLS deployments, leaving much of the MLS band either quiet or under utilised; Spectrum at 5 GHz presents enormous potential for revenue to short range, wideband wireless networking OEMs (e.g., /16 vendors); Spectrum auctions in or near this band present potential revenue streams for the governments. Page 58 Final Edition Number: 1.0

71 The combination of these factors has reinforced the need to justify the continued use of this spectrum for aviation purposes. Due to under utilised portions of the C band it is considered that introduction of an e system can be achieved without affecting MLS operation Assessment level This criterion is passed Openness of the Standard IEEE Standards documents are developed within the IEEE Societies and the Standards Coordinating Committees of the IEEE Standards Association (IEEE-SA) Standards Board. The IEEE develops its standards through a consensus development process, approved by the American National Standards Institute, which brings together volunteers representing varied viewpoints and interests to achieve the final product. Volunteers are not necessarily members of the Institute and serve without compensation. While the IEEE administers the process and establishes rules to promote fairness in the consensus development process, the IEEE does not independently evaluate, test, or verify the accuracy of any of the information contained in its standards. WiMax (the Worldwide Interoperability for Microwave Access Forum) is a non-profit corporation formed by equipment and component suppliers, including Intel Corporation, to promote the adoption of IEEE compliant equipment by operators of broadband wireless access systems. The organization is working to facilitate the deployment of broadband wireless networks based on the IEEE standard by helping to ensure the compatibility and interoperability of broadband wireless access equipment. In an effort to bring interoperability to Broadband Wireless Access, WiMax is focusing its efforts on establishing a unique subset of baseline features grouped in what is referred to as System Profiles that all compliant equipment must satisfy. These profiles will establish a baseline protocol that allows equipment from multiple vendors to interoperate, and that also provides system integrators and service providers with the ability to purchase equipment from more than one supplier. System Profiles can address the regulatory spectrum constraints faced by operators in different geographies. For example, a service provider in Europe operating in the 3.5 GHz band who has been allocated 14 MHz of spectrum is likely to want equipment that supports 3.5 and/or 7 MHz channel bandwidths and TDD (timedivision duplex) or FDD (frequency-division duplex) operation. Similarly, a service provider in the U.S. using license exempt spectrum in the 5.8 GHz band may desire equipment that supports TDD and a 10 MHz bandwidth. WiMax will establish a structured compliance procedure based upon the proven test methodology specified by ISO/IEC 9646 IEEE e is an open and mature standard, with equipment and component suppliers providing a profiled interoperable implementation. Edition Number: 1.0 Final Page 59

72 Assessment level This criterion is passed Desirable Criteria Robustness of the RF signal A number of different modulation schemes are supported including an efficient 64 QAM for good signal conditions,16 QAM and QPSK in intermediate conditions and a robust BPSK encoding is available for poorer propagation. A number of FEC techniques are defined for adoption including tail-biting, convolutional coding, block turbo coding and convolutional turbo codes. Additional features include: Scaling of the Fast Fourier Transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths ( MHz). Constant carrier spacing results in higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as Scalable OFDMA (SOFDMA). Improved NLOS coverage by utilizing advanced antenna diversity schemes, and hybrid-automatic Retransmission Request (harq) Improved coverage by introducing Adaptive Antenna Systems (AAS) and Multiple Input Multiple Output (MIMO) technology Increasing system gain by use of denser sub-channelisation, thereby improving indoor penetration High-performance coding techniques such as Turbo Coding and Low-Density Parity Check (LDPC), enhancing security and NLOS performance Downlink sub-channelisation, allowing administrators to trade coverage for capacity or vice versa Enhanced Fast Fourier Transform algorithm can tolerate larger delay spreads, increasing resistance to multipath interference Extra QoS class (enhanced real-time Polling Service) more appropriate for VoIP applications. Robustness of signal is assessed at criterion level TRL The WiMax market is at the interoperability testing stage with equipment vendors participating at plugfeast events to fine tune their interpretations of their e products. This process will lead to WiMax formal certification. In addition - Commercial implementations of e based on the WiMax profile are beginning to come to market. Ref 11-2 contains field studies at a number of varying airports sizes profiling wireless technologies with in the C band. Page 60 Final Edition Number: 1.0

73 802.16e is evaluated at TRL 6: Technology system / subsystem model or prototype demonstration in a relevant environment. The TRL assessed at criterion level of Flexibility Flexibility of modulation, forward error correction, architectural options and features result in a variety of performance values. A value has been given to this criterion of Ground Infrastructure cost If a COTS implementation is chosen the infrastructure cost could be relatively inexpensive. Exacting bespoke implementations would require development increasing the cost. Overall e offers a relatively simple ground infrastructure compared to peer candidates. However comparison with a VHF system is difficult as no equivalent service exists apart from ACARS and some deployment of system based on x. Consequently a criterion value of between 2 and 3 is given Performance Based Criteria Services supported This technology is only applicable in the surface domain providing voice and data in Unicast and broadcast modes between static and mobile subscribers up to speeds of 60 miles/hour Ability to meet requirements The ability of e to meet the requirements is very dependent on the propagation conditions and deployment of the system at an airport. As noted in Ref 11-2 the wireless channel in the C band in airport surface areas is a very dispersive fading channel, which is, over moderate durations (on the order of tens of milliseconds to a second, depending upon velocity), statistically non-stationary. For surface velocities up to 100 miles/hour, the channel will nonetheless be slowly fading for signalling rates larger than approximately 100 kbps. For smaller velocities, the fading is very slow for even lower signalling rates (e.g., for a velocity of 10 miles/hour, fading is very slow for any signalling rate above about 10 kbps). Thus, for all but the most narrowband transmissions, the Doppler spread induced upon signals by the multipath channel will be small, and hence the shape of the Doppler power spectrum will be immaterial to system performance. The worst-case channels occur in large airports, in Non Line Of Sight (NLOS) regions. These channel models contain a large number of multipath components, whose amplitudes fade randomly and often deeply, and as mentioned, in a correlated fashion. The channels measured in the small airports were less dispersive than those in the large and medium airports. Edition Number: 1.0 Final Page 61

74 Confirmation of the performance of an e based system needs to be undertaken through trials at representative airports. Airport Surface Airport zone TMA, Enroute ORP AOA Air/Ground Addressed Data Air/Air Addressed Data Air/Ground Broadcast Data Air/Air Broadcast Data Overall conclusion Of the candidates that meet the requirement for the airport surface, e has the largest data capacity, a simple ground infrastructure, and a developed standard on which to draw and appears to be the most applicable. IEEE e commercial adoption will expand rapidly in the short to medium timeframes which can benefit aviation. Intel chipsets are currently available for building WiMax. The trade-off is between inexpensive COTS implementations of the standard that may not fulfil all the criteria and a purpose built implementation profiled against an exacting specification. Aviation can benefit from the work already undertaken in developing the e standard and identify those features that can become the basis of a new aviation standard (e.g eAV). This will require considerable design and validation activity followed by trials in an airport environment Summary table The following figure summarises IEEE e based technology against the Class 2 template defined in the assessment methodology. The shaded cells indicate the results of the assessment. Page 62 Final Edition Number: 1.0

75 Spectrum Compatibility Open stds 3 4 Class 2 5 Criteri on Value 1 2 RF robustness TRL Flexibility Cost Capacit y Integrity Availability Latenc y Legend Achieved Inconclusive Failed Edition Number: 1.0 Final Page 63

76 12. RANKING OF THE TECHNOLOGIES Based on the application of the assessment criteria the following table indicates the Class assigned to each technology. In ranking the technologies a system based on the e standard was indicated as the most suited to meeting the intended required service volume i.e. Class 2 for the airport surface. For the L-band technologies none apart from WCDMA were rejected and all had some capability to meet some or all of the requirements. For WCDMA rejection was mainly based on the impracticality to deploy the technology in the L-band based on current information. Of the other proposed technologies B-AMC was evaluated as having the most evidence in its ability to meet the requirements. The other L-band technologies (P34, AMACS, LDL) were considered less advanced in demonstrating they could meet the requirements. However as each technology had particular benefits none could be rejected at this stage. As the only satellite system considered in detail, SBB was rejected primarily due to the inability to guarantee performance to meet ATS requirements due to technical limitations. It should be noted that SBB is not currently being offered for ATS applications anyway. In addition, the lifetime of the I-4 satellites will reach the end of their life around 2020 and consequently it is unlikely that this will be available the timeframe of the FCI. The table below summarises the outcome of the classification for each technology together with the proposed frequency of operation and application airspace. Technology Class Frequency band Application airspace e 2 C-Band Airport surface B-AMC 3 L-Band Airport surface, TMA, En-route P34 902) (TIA- 4 AMACS 4 LDL 4 L- Band Airport surface, TMA, En L-Band Airport surface, TMA, En L-Band Airport surface, TMA, En Table 12-1 Technologies against evaluation Class Page 64 Final Edition Number: 1.0

77 13. GENERAL CONCLUSIONS The technology assessment has undertaken a logical series of activities to investigate a wide range of potential technologies which could be used as the basis for new components of the Future Communications Infrastructure (FCI). These will be needed to meet the future needs of air/ground and air/air communication to support air traffic service (ATS) and airline operational control (AOC) in the timeframe of as identified under the Phase 2 in the Communication Operating Concept and Requirements (COCR) document. The COCR identifies the need for requirements on the quality of services from the end-toend communication chain. This includes not only availability, integrity and continuity but also greater repeatability in the required performance i.e. the communications performance should be able to be determined within a small range of tolerance. Conclusion 1: The FCI must support ATS and AOC end-to-end communications including air/ground and air/air communications. The COCR identifies that in the timeframe normal means of communication will be by data. It is envisaged that ATS communication will evolve from the current mainly voicebased method to one where data link exchanges becomes the normal means of communications between air traffic controllers and pilots. Currently much of AOC is already based on data link e.g. ACARS applications and this is likely to grow over time particularly with the introduction of capabilities such as Electronic Flight Bags (EFBs). In this timeframe voice will be used for unusual or emergency communications. The requirements for this type of voice communication are the same as currently available with VHF DSB-AM technology. These requirements are foreseen to continue to be met by existing technology therefore the primary need for the new components are for data communication. Although some of the short-listed technologies can support digital voice the focus has been for data communications and therefore a digital voice capability was not a discriminator in the assessment. However digital voice is still a desirable feature in the longer term. Therefore new components will be introduced into the FCI to meet the needs of these future data communication requirements. Conclusion 2: New air/ground and air/air communication components of the FCI will be required to primarily support data communications. From consideration of the requirements in the diverse types of airspace in which ATS and AOC communication is required, as identified in the COCR, it has emerged that no single technology can meet all the requirements. Conclusion 3 No single communications technology can meet all the requirements in all airspace The FCI will be a system of systems with different technologies, some legacy and with new components. The FCI will include existing voice and data capabilities such as DSB-AM analogue voice technology, satellite communication and VDL M2. The FCI will continue to use to the greatest extent possible existing technologies. However it is expected to evolve Edition Number: 1.0 Final Page 65

78 over time to offer the communication capability to meet the growth in air traffic and new requirements to achieve safe and efficient management of aircraft. The minimum numbers of technologies will be utilised within the FCI for reliable and economic end-to-end communication within the operational context being supported. Conclusion 4 - To meet the diverse range of communications in all airspace the FCI will comprise the minimum numbers of air/ground and air/air technologies to meet the operational requirements. The technology assessment has investigated a wide range of emerging new technology and standards for adoption as new components of the FCI. Although there will be further development in communication technology, due to the time to deploy and the need for stable technology solutions, the reuse of emerging technology offers the lowest risk option. Some of the technologies considered are available as commercial-off-the-shelf solutions for the areas of application for which they were designed but not in an aviation band. The results of the technology assessment have not identified any technology that does not require some form of modification; no one COTS solution that can be deployed without modification. The minimum modification required is to change the frequency of operation to one of the target aviation bands or modification of standard. Other changes are dependent on the design of the technologies and often are related to modification of the physical layer e.g. the modulation scheme. Despite this there are still considered to be benefits in adopting COTS components wherever possible to minimise design effort, reduce risk and to shorten time to deployment. Conclusion 5 No COTS technology has been identified that can be adopted as new components of the FCI without some modification. However reuse of emerging technology and standards should be considered to the maximum extent possible to reduce risk and shorten development time. In line with the current activity within the ICAO ACP to include the Internet Protocol Suite (IPS) within the ATN it has been assumed that the new components of the FCI will operate within an IP environment. Assumption 1: The FRS will operate within an IP infrastructure Page 66 Final Edition Number: 1.0

79 14. TECHNOLOGY ASSESSMENT CONCLUSIONS AND RECOMMENDATIONS 14.1 Short listed technologies against frequency bands The following technologies have been identified as the most suitable for the target bands of operation. These take into account the ranking and the influence of the essential criterion, which is co-existence in the target band with current users VHF band Existing VHF AM(R)S band For the foreseeable future there are no opportunities to introduce new technology in this band Extended VHF Band No technology was identified for deployment in this band at this time. However this extension band has potential for communications systems subject to WRC07 discussions. The initial use of this band could be for expansion of current DSB-AM. In the very long term there is potential for the introduction of new AM(R)S technology. Recommendation the VHF extension band (subject to WRC07) could be used initially to support expansion of communication services using existing technology. In the longer term new technologies may be considered for operation in this band L-Band This band is a challenging environment for aeronautical communications due to the aeronautical channel characteristics and the current usage of the band. For example, estimated RMS delay spreads for this channel, in the order of 1.4 ms, can lead to frequency selective fading performance for some technologies. No one system assessed can be recommended for deployment in this band without further studies. Studies of B-AMC have suggested that it may be able to be used as an in-lay technology between the DME frequencies. However the study did recognise that further work was required to overcome the inconsistency of input data and the lack of common metrics for interference investigations. Similar conclusions were noted for the other L-band candidate technologies. This is the most urgent issue to be addressed in concluding compatibility in the L-band. Recommendation it is necessary to establish comprehensive common assumptions and common interference evaluation criteria for all candidate L band technologies and to review the results of the calculations (or repeat calculations) undertaken in the assessment. Edition Number: 1.0 Final Page 67

80 Considering these features and the most promising candidates, two options for the L-band Digital Aeronautical Communication System (L-DACS) were identified. These options warrant further consideration before final selection of a data link technology. The first option represents the state of the art in the commercial developments employing modern modulation techniques and may lead to utilisation/adaptation of commercial products and standards. The second capitalises on experience from aviation specific systems and standards such as the VDL3, VDL4 and UAT. The first option for L-DACS includes a frequency division duplex (FDD) configuration utilizing OFDM modulation techniques, reservation based access control and advanced network protocols. This solution is a derivative of the B-AMC and TIA-902 (P34) technologies. The second L-DACS option includes a time division duplex (TDD) configuration utilizing a binary modulation derivative of the implemented UAT system (CPFSK family) and of existing commercial (e.g. GSM) systems and custom protocols for lower layers providing high qualityof-service management capability. This solution is a derivative of the LDL and AMACS technologies. Table 2 depicts the two options Option 1 - OFDM/FDD based This grouping has some interesting features characterised by Frequency division duplex system with contemporary modulation physical layer P34 (TIA-902)/B-AMC derivative: OFDM ( khz channels); QPSK/QAM-16; Reservation-based Channel Contention; User/Message Encryption; Mobility Management; ATN/IP subnetwork interface support This grouping draws heavily on state-of-the-art emerging COTS systems and techniques Option 2 - Narrowband/TDD An alternative grouping consists of features of emerging tailored systems. AMACS offers a customized design which could be tailored for aviation and it that it is reusing experience from other aviation systems. AMACS is expected to support a/a communications. However of concern is the lack of sufficient information to evaluate the system and the current maturity level. LDL/AMACS derivative: CP-FSK/GMSK ( khz channels); Reservationbased Channel Contention; Handoff Support; ATN/IP subnetwork interface support Access scheme Modulation type Origins L-DACS 1 FDD OFDM B-AMC, TIA 902 (P34) L-DACS 2 TDD CPFSK/GMSK type LDL, AMACS Table L-DACS (the L-band data link) options key characteristics To finalise the selection of the most suitable solution the following issues need to be completed. Page 68 Final Edition Number: 1.0

81 As a matter of urgency complete investigation of the compatibility of candidate L- DACS components with existing systems in the L-band particularly onboard co-site interference. This will require finalisation of the overall design including design tradeoffs, power control, etc. and the confirmation that the final system can meet the performance requirements. Simulation of specified system performance including o Interference to/from existing L-band users o Confirm performance in the anticipated channel environment (using an L-band channel model) o Confirm performance and ability to meet COCR service requirements o Definition of common interference criteria to validate solution interference performance in L-band o Produce prototype and carry out interference assessment by acquiring/developing software defined radio in which to develop the L-DACS options o Conduct interference measurement tests Refine the air-air communications capability offered by B-AMC, AMACS and P34 and undertake simulations to confirm performance. In particular investigate the method of operation in which the air-air and air-ground capability can work simultaneously and identify any mutual interference effects. Develop harmonized technology recommendations for the selected L-DACS for input to a global aeronautical standardisation activity. Apply common assessment criteria Document final results and expose to appropriate Stakeholders and standards bodies C-Band A technology based on elements of the IEEE e standard is recommended for use in this band as it has the following properties - Well matched to the airport applications in terms of capability and performance designed to work in this band and initial evaluations in the modelled aeronautical MLS band show favourable results supported by private service providers. Many have shown interest in the 802.xx family of wireless protocols (favourable business case that may be driven by factors beyond ATS and AOC communications, e.g. airport authorities) However additional work is required to choose from the wide range of options within the standard to tailor it to the aviation environment. The resulting work will culminate in initiation of common global standard development process. Recommendation IEEE e is the preferred candidate for airport surface applications and a common global standard should be developed for aviation applications e.g eAV. To finalise the options for the deployment of e the following further work should be undertaken to tailor the system to the aviation environment. The results need to be confirmed in trials in example airport locations large and small. Newly restarted work to develop the IEEE may also be considered in developing the aviation standard. Edition Number: 1.0 Final Page 69

82 The following areas of work are required - Pursue validation and implementation of e technology for provision of aeronautical airport surface data link communications. In particular identify the specific elements from this complex standard that best meets aviation requirements. These choices need to be supported by laboratory testing and complemented by trials at representative airports (small, medium, large) on test vehicles and then on aircraft. The results should be captured in an aviation specific e standard e.g eAv. Specify patches for identified deficiencies Specify receiver implementation Specify avionics architecture for each applicable aircraft configuration Specify Receiver and Transmitter Conformance Tests Validation activities including - o Analysis and simulations to prove completeness of standards o Develop prototype radios and conduct tests in the airport environment o Validate interference performance with additional measurements AMS(R)S Band Aeronautical satellite systems are the most promising technology for providing communication in oceanic and remote areas. In addition they potentially have the capability to supplement coverage of terrestrial systems in higher density airspace provide they can meet the requirements. Note : other beyond the horizon technologies such as HF data links are being used currently and will continue to do so. Enhancements to HF data links are being considered currently and could offer improvements for both voice and data communications in the short to medium term. The Inmarsat SwiftBroadband system which was evaluated in the FCS is likely to be reaching the end of its life around 2020 and therefore cannot be considered as an element of the FCI beyond this timescale. In addition, it currently does not have all features necessary to guarantee the quality of service to support safety-related communications. Priority and preemption are some of the features that would be expected in any future satellite system if it offered a service to a range of users which included non-safety communication. Emerging satellite technology such as the ESA ATM SATCOM are being designed to meet the requirements for safety related communication i.e. ATS and AOC taking into account their special needs compared to non-safety communication. Such satellite systems could offer a complementary communication service in areas where high availability is required and cannot be achieved by a terrestrial system. Other systems such as Iridium NEXT may also have the potential to support safety-related communications. Therefore it is recommended to investigate specific satellite service development by contributing to the definition of requirements and to participate in trial activity. This should be done in the context of developing a common open standard for a common global satellite Page 70 Final Edition Number: 1.0

83 service as defined in the essential criteria. Such open standards will encourage the interoperability between systems. Recommendation continue to investigate the potential of new satellite system technology based on common open standards as potential for additional communication capability within the FCI. In parallel to progressing the technical design, activity must be undertaken to ensure that adequate spectrum is available within the AMS(R)S allocation to support increased use of satellite technology. Recommendation monitor activity to ensure that sufficient AMS(R)S spectrum is available FRS within the context of the Future Communications Infrastructure As mentioned in section 3, the future radio system will be a component of the FCI and will operate within an IP infrastructure. Further work on finalising the selection of the new components of the FCI should be carried out within an end-to-end IP environment to ensure that the performance can be achieved within a representative architecture. Recommendation to finalise the selection of the new components of the FCI trials should be carried out within an end-to-end IP environment to ensure that the performance can be achieved. Methods to guarantee the end-to-end quality of service should be defined. Edition Number: 1.0 Final Page 71

84 15. OVERALL CONCLUSIONS The VHF band in Europe is saturated and will remain so even with the introduction of more channels made possible with 8.33kHz channel spacing. To meet the requirements emerging from applications anticipated within the SESAR development programme, new technology will be required to provide enhanced data communication. Some of these future requirements were identified in the COCR. The new communication technology operating within the FCI should utilise the potential in aviation spectrum outside the VHF band i.e. within the L-band and C-band. The L-band is suited to normal ATS communications at long and short range. The C-band is suited to short range and is therefore suitable for airport surface applications only. Despite considerable effort in modelling and simulation it is has not been possible to recommend a single technology that can operate in the L-band at this stage. This is due to two main reasons- 1. difficulty in conclusively confirming the compatibility with existing users of the L-band and 2. confirmation that the performance requirements can be met taking into account the need for spectrum compatibility. Based on the historical length of time to develop globally standardised aviation technologies, work to conclude on the final design of an L-DACS must start immediately to ensure the final system is availability for operational use by Satellite communication will continue to play an important role in future ATS/AOC communications. Although satellite communication has been considered so far only for use in low density oceanic and remote areas it may be possible to introduce it in high-density airspace to complement or even replace terrestrial systems provided the required performance can be achieved. Consequently investigations should continue into new satellite systems that may be able to meet the requirements of higher density airspace. For airport surface applications, a technology based on the IEEE e standard operating in the C-band is recommended. Such a system will have to be defined in standards based on e tailored to meet aviation requirements e.g eAV. This will require considerable design and validation effort to optimise it for the complex environment at airports especially larger ones. Newly restarted work to develop the IEEE may also be considered in developing the aviation standard. All of the above technologies will require to be standardised for global use through appropriate bodies such as ICAO, EUROCAE, RTCA and AEEC. Page 72 Final Edition Number: 1.0

85 APPENDIX A. - REFERENCE DOCUMENTS The primary references used in this document in addition to the technology specific one are listed below - 1 EUROCONTROL/FAA Communications Operating Concept and Requirements (COCR) v2.0, April EUROCONTROL, Future Communications Infrastructure - Technology Investigations Step 1: Initial Technology Shortlist, QinetiQ, September EUROCONTROL, Future Communications Infrastructure - Technology Investigations Step 2: Assessment Methodology, QinetiQ, May EUROCONTROL, Future Communications Infrastructure - Technology Investigations. Evaluation Scenarios draft AENA - Framework for Spectrum Compatibility Analysis in L-Band for FCI technology Candidates version ICAO Annex 10 Volume V Aeronautical Radio Frequency Spectrum Utilisation 7 EUROCONTROL - Standard Inputs for EUROCONTROL Cost Benefit Analyses 2005 Edition 8 Wireless Channel Characterization in the 5 GHz Microwave Landing System Extension Band for Airport Surface Areas - Final Project Report for NASA ACAST, Ohio University 9 Identification of Technologies for Provision of Future Aeronautical Communications, NASA/CR EUROCONTROL study on FCI Architecture and End Systems - A/G Study Results January 2007 available from udy%20results.zip 11 NASA - Identification of Technologies for Provision of Future Aeronautical Communications NASA/CR ITT, October See Ref 5-4 in B-AMC section Future Communication Study- Technology Pre-Screening version 0.92, EUROCONTROL and QinetiQ, December ACPWGT/1-WP06: Future Communication Study - Action Plan 17, Final Conclusions and Recommendations Report Edition Number: 1.0 Final Page 73

86 APPENDIX B. AMACS TECHNICAL DESCRIPTION B.1.1 Overview AMACS is a multipurpose communication system, with cellular narrowband ( khz), operating in the MHz frequency allocation designed for flexible deployment. Its key design drivers are flexibility, scalability and robustness. E-TDMA and XDL4 concepts have been merged to provide an adapted technical solution for the data-link communications needs of The AMACS concept is intended to provide a data-only service with significant requirements for QoS for air/ground point to point, air/air point to point and broadcast modes. Its flexible slot structure is adaptable to meet local requirements. It can support different channel bandwidths and bit rates to cope with the various operational needs and traffic densities foreseen for Europe in the future. Its robust physical layer is based on the GSM/UAT modulation types associated with strong data coding, for achieving the highest QoS in terms of latency. A multi-level QoS system is proposed to permit use of channel resources according to the QoS level required. Specific channel slots are reserved for high QoS transmissions. The efficient handling of QoS is based on the TDMA structured MAC layer and gives a guaranteed transmission delay. These communications can be supported by the ATN - network either current protocol or IPS based. Common Signalling Channels (CSC), similar to those employed by VDL Mode 4, are proposed to maintain QoS levels during intervals of network degradation. Examples are the warm- and cold-start features if a ground station (or stations) should go off-line for any reason. CSCs would serve to broadcast new ground station frequencies to alert aircraft mobiles of the new channels to which they should tune. The AMACS frame length is designed for fast delivery of time-critical messages and has been set at 2 seconds, but could be adapted to a lower duration if necessary. B.1.2 Design goals The AMACS concept is based on several fundamental performance requirements. These include: 1) A very robust physical layer using the already-validated modulation family (CPFSK) used by GSM or UAT. 2) Contributions to data integrity and certification goals through careful, fast, error detection and correction mechanisms. 3) Use of modular error correction where a unique FEC code is used for headers and for short and long slot data. 4) A high-integrity deterministic MAC sublayer employing deterministic slot scheduling and potentially Statistical Self-Synchronization (S3) and deterministic slot scheduling for remote area applications (without ground stations). 5) For ranging functions, fairly imprecise positioning performance may be adequate. 6) High throughput using low overhead for headers, FEC, and transmitter ramping. Edition Number: 1.0 Final Page 74

87 AMACS is designed to simultaneously handle up to 175 aircraft per cell in high-density airspace. It has an efficient air-initiated cell handover mechanism, which uses aircraft knowledge of cell locations and characteristics through on-board databases, Electronic Flight Bags (EFB) or a Common Signalling Channel (CSC). Its initial deployment will be in the lower L-band for new ATM point-to-point services requiring a high QoS, thus giving support to SESAR or NextGen future concept. Broadcast services will be provided in a segregated channel if the spectrum availability in the lower L-band is sufficient. Air-to-air data point to point communication is also provided in other segregated channels. It is expected that AOC data communications can be achieved if the necessary extra spectrum is available. B.1.3 Air Interface Description: PHY, MAC, Data-link & Network Sub-layers B Physical & MAC Sub-layers The aim is to re-use where appropriate the physical layer specifications of the UAT/GSM systems, thus affording considerable advantage in the costs associated with the development, standardization and fielding of the technology. The derivation of the necessary physical layer properties is explained below. The system performance is designed to provide a required Residual Message Error Rate (MER) of 10-7 on the basis of a Physical Bit Error Rate of The target net data rate is about 500 kbps in order to accommodate the most demanding communications load requirement in high density airspace (ref. COCR v2). These are summarized in Table B-1 and Table B-2 for addressed and broadcast services in high density airspace. Airport Surface TMA Enroute Oceanic ATS AOC Combined Table B-1 COCR addressed communications load (kbps) for combined uplink and downlink in High Density volumes Airport Surface TMA Enroute Oceanic C&P SURV ITP SURV M&S SURV SURV TIS-B Table B-2 COCR broadcast communications load (kbps) in post 2020 Edition Number: 1.0 Final Page 75

88 The figures in Table B-2 are for individual services the aggregate loading figure is close to 500 kbps. Previous work on E-TDMA has led to the definition of framing and error correcting codes. Much of this remains applicable to the design requirements of the AMACS system. B Modulation Although AMACS makes use of UAT and VDL Mode 4 characteristics, it is not essential for AMACS to use the same modulation schemes. A balance has to be struck between the bit rate, the Bit-Error Rate (BER), the Signal-to-Noise Ration (SNR), the bandwidth and power. A description of possible modulation schemes and an analysis of the proposals which could be used for AMACS are presented in Ref 4-1 in section 4.1 of this report. Modulation design choice Given the fundamental principles of GMSK modulation shown in Ref 4-1 in section 4.1, three proposals were drawn up taking into consideration the desirable characteristics, design goals, and the spectral environment that define the theatre of operations for AMACS. In light of the observations, the known spectral constraints in the L-band, and cost advantages from reusing mass-market standards, the GMSK modulation proposal represents the best design compromise and is the design choice for the AMACS physical specifications. Chosen proposal : GMSK : h = 0.5 & BT = 0.3 Gross bit rate : ~ 540 kbps Channel bandwidth : 400 khz Expected C/I : ~ 9dB The use of concatenated error coding is considered in Ref 4-1 in section 4.1, to make the objective of a C/I of 9 db in co-channel interference attainable. Introduction: Point-to-Point Air Interface The AMACS system makes use of a specific channel for point-to-point communications. This channel is designed to allow stations (air and ground) to have a minimum number of exclusive bits per slot for regular or high-qos transmissions, with more bits available on request. The broadcast air interface description is given in Section B Impact of the physical layer features on airborne co-site issues One of the key problems for a future communication component operating in the L-band ( MHz) is co-siting with other radio transmitters that operate in the same frequency band. Even if a frequency separation is implemented, providing some decoupling with other spurious emissions, the robustness of the new communication link will be drastically affected by the proximity of other pulse transmitters on the same aircraft. Page 76 Final Edition Number: 1.0

89 Therefore the best solution will be to take advantage of Pulse Blanking Techniques that have been used in many cases to reduce the effect of strong interference (that is, the case on board aircraft due to very small system isolation). Such a pulse blanking mechanism has been defined in the UAT standards and has a common bus interconnecting the avionics elements that could benefit from the information provided (pulse blanking signal whenever a transmitter is on). Taking into account that two of the major interferers for the new communication system will be short pulsing transmitters (DME and SSR/Mode S), the duration of the jamming pulses will be equivalent to or lower than the AMACS bit duration: the impact of the interference will be therefore limited to a few bits in the frame for which data coding (presented in Section 0) will be the appropriate answer to mitigate the impact of the interference on the frame error rate. On the other hand the impact of AMACS onboard implementation on DME or SSR/Mode S will be limited by providing a frequency separation between the AMACS channel and the first DME receiving channel (i.e. 978 MHz) and by taking into account the small duty cycle of AMACS (0.15% is the minimum duty cycle per aircraft on the basis of a 3ms usable slot duration, on average the aggregated duty cycle per aircraft should not.5 %). Power control option In order to reduce the level of interference for point-to-point, a power control option is possible. This can be done rather easily, using a small capacity in the signalling channels (afforded by the high capacity offered by the GMSK modulation option). It requires the ground base station to perform a continuous measurement of the received signals from each aircraft and then return this information to each aircraft. On reception of this information, the aircraft terminal uses it to feed a power control algorithm, which is an adaptive algorithm that converges to the optimum power, i.e. the power which is required for normal operations and acceptable BER. Advantage can be taken from algorithms developed for GSM. Access and frame structure For point-to-point channels, AMACS will use the MAC layer principles developed for E- TDMA. It will have deterministic organization and a deterministic access to the medium. AMACS will have a frame repeating every 2 seconds, with specific 'uplink' and 'downlink' sections. The frames are presented in Figure B.1. frame (N-1) AMACS cycle frame (N) AMACS cycle frame (N+1) AMACS cycle Figure B.1 AMACS Frames Edition Number: 1.0 Final Page 77

90 A frame consists of multiple slots and a slot consists of one burst. A frame is composed of successive time slots that each consists of: transmitter ramp-up, synchronization interval, flags and addresses, the data burst, FEC/CRC code bits, transmitter ramp-down, propagation guard time. This slot structure is depicted in Figure B.2. individual slot structure Ramp-up Synch signalling and data active slot duration FEC/ CRC decay Guard time depending on cell size next slot total slot duration 4ms Figure B.2 AMACS slot structure If a ground station or an aircraft is using several slots for one transmission, then the transmitted ramp-up time and synchronization interval will only be present at the start of the initial slot, and the transmitter ramp-down time and propagation guard time will only be present at the end of the last slot (the number and position of the FEC/CRC code bits will be dependent on the size of the transmission). This means that the size of the combined signalling and data bursts will be larger than the sum of signalling and data burst sections from separate, individual slots (the extra bit transmission capacity is of the order of 540 bits). This is shown in Figure B.3. Page 78 Final Edition Number: 1.0

91 merged slot structure ramp-up synch signalling and data FEC/ CRC signalling and data FEC, CRC and decay guard time depending on cell size next slot total slot duration total slot duration Figure B.3 AMACS merged slot structure Figure B.4 shows a different view of the slot structure, showing the actual number of bits allocated to each section. It is based on a frame size of 2 seconds, a data rate of 540 kbps and a slot size of 4ms. 4 ms Ramp up Flag Addresses plus flags User data n 1 octet 4 5 octets (typical) 148 octets Reservation header FEC / CRC Flag Guard time Ramp down 3 octets (if required) 47 octets 1 octet 0 9 ms m Figure B.4 AMACS slot structure sizes The combined ramp-up and ramp-down time (m+n) is less than 0 1 ms. Edition Number: 1.0 Final Page 79

92 Slot characteristics: Active slot length: 4 ms (ramp + guard times) = 3 ms Bits per slot: Active slot length Bit rate = 1,620 bits Bits for FEC/CRC: ~30% of bits per slot = 376 bits Remainder: Bits per slot CRC = 1,244 bits = octets ISO flags + reservation header = 3 octets Addresses plus administrative flags (typical) = 4 5 octets User data space = 148 octets The use of the uplink sections in the frame is configurable (dynamically) by the ground station. These sections are ground-reserved areas for uplinks and ground-directed signalling. The two downlink sections are separated for different Classes of Service (CoS). The first one (CoS1) is intended for a high QoS and each aircraft is allocated one exclusive downlink slot in CoS1 for high QoS messages. More downlink slots are available on request in the lower QoS section (CoS2). The slots are allocated based on QoS requirements, and may be based on the application or may be functionally grouped. Figure B.5 illustrates this concept. Start of UTC second Frame UP1 CoS1 UP2 CoS2 Framing message Cell insertion Reserved slots for uplink messages Exclusive primary slots for short, high QoS messages or RTS messages Second uplink for ACKs, CTS, reservations Shared slots, reserved or random access: used for any messages Uplink section Downlink section Uplink section Shared section Figure B.5 AMACS Frame Structure Page 80 Final Edition Number: 1.0

93 Frame section usage In Figure B.5, the CoS levels indicate service delivery levels. For the highest level, a dedicated time slot is reserved in CoS1 for each aircraft in the cell, and transit times and minimum throughput rates are guaranteed. The use of deterministic slot assignments is important for QoS performance. For the lower-level CoS2 time slots, the time guarantees are smaller since these slots are potentially shared among many aircraft and time guarantees are measured statistically. Specific uplink slots are reserved in each frame for the ground station framing message and for cell insertion messages. It is expected that the messages required for hand-off procedures will normally be exchanged in the UP1 and CoS1 sections, thereby taking place within one frame. The section lengths are not fixed and can be optimized by the ground station. The ground station will broadcast a framing message to all aircraft within the cell to indicate section length changes. Only the slot size and the overall frame size are fixed. If the ground station intends to change the frame section sizes, the aircraft will be notified a long time in advance (typically up to a few minutes). Proposed messages required for AMACS are provided in Ref 4-1 in section 4.1. These structures indicate the different message fields and the number of bits required for each message field. All except the longest messages will fit into the single slot shown in Figure B.4. System operation exchanges are provided in Ref 4-1 in section 4.1, indicating how the aircraft and the ground station interact using the proposed messages. Message identifiers and acknowledgements The 'message identifier' fields are used in addition to the message type fields so that stations can be certain of which of their transmissions have been acknowledged. (For example, a long data message could be transmitted in several parts, and if one part is not correctly received it would be inefficient to have to retransmit the whole message) The identifier acts as a rolling sequence number, which can have values from 1 to 64. This range is acceptable because it is not necessary for every message to have a unique ID, merely for the messages from a station to be distinguishable within a period of time. The receiving station will include the message identifier in its acknowledgements so that they show which of the individual messages have been received; the message type field on its own would not be sufficient. Insertion mechanism for an aircraft entering the cell An aircraft entering the cell will know (from on-board information) the frequency of the ground station in the new cell. Edition Number: 1.0 Final Page 81

94 It will listen on this frequency for the framing message transmitted by the ground station, which contains information about the slot structure, and will then announce its presence to the ground station by transmitting a message in one of the dedicated cell insertion slots. The ground station will reply in UP1 in the following frame, telling the aircraft the position of its allocated high-qos slot in the CoS1 section. It will also give the aircraft a local address, used in the cell for identification instead of the longer 27-bit ICAO address. It is expected that the aircraft will be able to transmit in its allocated CoS1 slot very soon after reaching the new cell (as a framing message is transmitted by the ground station every 2 seconds). Reservation mechanism for downlink In order to reserve a slot or a series of slots in the CoS2 section of the frame, the aircraft includes a reservation request for CoS2 slots in its CoS1 slot transmission. These CoS2 slots are likely to be required when the aircraft has a large amount of data to transmit which cannot all be fitted into the CoS1 slot. A reservation flag (RTS) is set in the CoS1 slot transmission by the requesting aircraft and notice is implicitly provided to all members of the channel that future timeslots are requested by that aircraft. A reservation echo (CTS) is transmitted by the ground station, acknowledging and granting the request for time slots within the pool of secondary slots available in CoS2. An aircraft may also transmit a slot reservation request (RTS) in CoS2 if it has further information to send to the ground station in the same frame. The ground station will reply in the first available slot, indicating whether or not any slots are available for the aircraft to use. If slots are available, the ground station will transmit a CTS identifying the available slots. If none are free then the aircraft will have to transmit in the next frame. In order to prevent conflicting transmissions, all aircraft will listen to all CTS transmissions to record in their reservation tables which slots have been reserved. Uplink transmissions The ground station has two blocks in each frame, UP1 and UP2, which are reserved for uplink transmissions. These are used by the ground station for normal data transmissions to aircraft, acknowledgements to downlink messages, CTS messages and cell insertion and exit exchanges. The slots in the uplink section are concatenated and do not require separate ramp-up and ramp-down nor guard-time in between messages. Consequently the number of bits available for data transmission within each slot is greater. If the ground station requires more slots for uplink transmissions, it will examine the reservation table for CoS2 and then broadcast a block reservation message to all aircraft. This message will indicate the start and number of slots of the reservation, which will only apply to the current frame. No aircraft will transmit in this block. Page 82 Final Edition Number: 1.0

95 Hand-off mechanism for an aircraft leaving the cell There are two possible means of hand-off: controlled and uncontrolled. Controlled hand-off Controlled hand-offs can be air-initiated or ground-requested air-initiated. An aircraft will know, from on-board information, when it is nearing the edge of the current cell. At an appropriate time, it will transmit a "cell exit" message in its dedicated CoS1 slot. The ground station will reply, in a UP2 slot, to confirm that the aircraft is leaving the cell and to indicate the number of a reserved CoS2 slot. As the "cell exit" message is being transmitted, the aircraft will also be searching for the ground station of the next cell, to ensure continuity of communications. When the aircraft receives the "exit confirmation" message, it will send a normal ACK message in this CoS2 slot, indicating that it is the "exit confirmation" message which is being acknowledged (this will be the last message that the aircraft sends to the ground station). When the ground station receives the ACK message from the aircraft, it will de-allocate the aircraft's CoS1 slot and will consider the link to be terminated. The ground-requested procedure is very similar the ground station will know, from the location information in ADS-B transmissions, when an aircraft is nearing the edge of a cell. If the ground station determines that a hand-off is appropriate, it will transmit a "cell exit" message to the aircraft. The aircraft, on receiving it, will attempt communication with the ground station in the next cell. If this is successful and the aircraft is allocated a CoS1 slot in the next cell, it will reply, in its current CoS1 slot, with an "exit confirmation" message. Then the current ground station will de-allocate the aircraft's CoS1 slot and will consider the link to be terminated. Otherwise the aircraft will maintain its communication with the current ground station. The hand-off from the current ground station will not be completed before the aircraft has made contact with the next cell. Uncontrolled hand-off If communication between the aircraft and the ground station is lost, for more than a predetermined time period, then both the aircraft and the ground station will consider their link to be terminated. The ground station will de-allocate the aircraft's CoS1 slot as it will assume that it is no longer required by the aircraft. The aircraft will determine the appropriate (new) ground station to contact and will begin the "cell insertion" procedure on the new frequency. For this process to occur correctly, the appropriate value for the time-out period must be chosen (as it may be affected by local factors). Edition Number: 1.0 Final Page 83

96 B Broadcast Air Interface The AMACS system makes use of a specific channel for broadcast communications. The AMACS broadcast channel has the same MAC structure as VDL Mode 4, modified for a single channel and for the AMACS frame structure. One superframe is 60 seconds long and contains 15,000 slots, with a corresponding slot length of 4 ms. This increase in the allowable basic message size makes AMACS more convenient for ADS-B. Each superframe starts with a short ground-quarantine section. The remaining slots are available to all stations (air and ground) by random access, using modified VDL Mode 4 reservation protocols. Most VDL Mode 4 broadcast protocols will be used, but no point-to-point transmissions will be permitted on the broadcast channel. Therefore some modifications will be required. B Data-link Sub-layer Segmentation and de-segmentation The data-link sub-layer will handle the segmentation of user data queued for transmission by higher layers into appropriate blocks for the MAC layer and the de-segmentation (reassembly) of received blocks from the MAC layer into a single user data packet for the upper layer. Transmission The overall size of the message will already be known. The user data will need segmentation into blocks if the message size exceeds the maximum for one slot, which is 145 octets. Each additional block can contain up to 208 octets of data. These blocks shall carry sequencing markers to indicate both the total number of blocks and each blocks place in the sequence. Reception On reception of user data blocks from the MAC layer, the data-link sub-layer will know (from the sequencing numbers) how many blocks to expect. The re-assembly of the blocks will be done by using the sequencing numbers; the sub-layer shall know that the first block contains 145 octets of the user data but that the other blocks may contain up to 208 octets. Error correcting scheme and interleaving A key factor of AMACS is provision of deterministic access to the radio channel to cover the stringent latency requirements of future data-link services. In order to achieve this goal it is not only necessary to provide the proper mechanism at the MAC layer to ensure deterministic access to each frame to any aircraft logged in a cell but also to ensure that the probability of message rejection due to data corruption is kept very low. This is only achievable through the use of specific data coding ensuring a high level of error corrections: Page 84 Final Edition Number: 1.0

97 this data coding will be therefore dependent on the QoS associated to the data (e.g. the useful data throughput will be lower for high QoS due to the level of associated data coding. Different error correcting schemes are used in data communications : cyclic block codes, convolutional codes, turbo code and low density parity check code. The focus has been on cyclic bloc codes. Ref 4-1 in section 4.1 provides the reasoning behind the choice of the Reed-Solomon (RS) and Bose, Chaudhuri and Hocquenghem (BCH) codes. B Network Sub-layer Figure B.6 and Figure B.7 present the end-to-end connectivity architecture involving the AMACS subnetwork. ATN Stack 1 ATN Stack ATN ground SNDCF WAN ATN Ground SNDCF WAN ATN AMACS SNDCF WAN 3 WAN 2 GNI AMACS datalink AMACS Physical 4 ATN AMACS SNDCF AMACS datalink AMACS Physical Ground router Air-Ground router AMACS Ground Station Airborne router Figure B.6 Protocols stack model for ATN Edition Number: 1.0 Final Page 85

98 TCP/IP Stack 1 TCP/IP Stack IP ground SNDCF WAN IP Ground SNDCF WAN IP Mobile AMACSS NDCF WAN 3 WAN 2 GNI AMACS datalink AMACS Physical 4 IP Mobile AMACS SNDCF AMACS datalink AMACS Physical Ground router Air-Ground router AMACS Ground Station Airborne router Figure B.7 Protocols stack model for TCP/IP These figures show the main associations: Association between end users: In the context of both ATN and TCP/IP communications, end-to-end connections are provided at the Transport level. Association between AMACS network service users: In the context of both ATN and TCP/IP communications, channels are established between an air-ground router and an airborne router. These channels are established in reference to the QoS. Compression mechanisms will be set up (e.g. Deflate). Association between the GNI and the Air-Ground router: The GNI will report aircraft connectivity to the Air-Ground router. This will be performed through use of Join and Leave messages. This interface will permit to handle the AMACS QoS management as defined in B Transfer of data between an airborne AMACS system and a GNI though an AMACS Ground Radio Station, using the AMACS medium access protocol. B Services offered by the network layer: Point-to-point air-ground Data transfer In the Airborne and Air/Ground routers, the data communication service is based on a dedicated AMACS SNDCF (which could be derived from the ATN Frame Mode SNDCF). The following data transfer services are provided: SN-Unitdata.request SN-Unitdata.Indication Two mobility management information events will be raised by the datalink layer and provided to the airborne router and the Air/Ground router: Join event, Page 86 Final Edition Number: 1.0

99 Leave event. These two events will be used as defined in Section B Following a join event, packets may be up-linked to the aircraft from the Air/Ground router or down-linked from the aircraft to the Air/Ground router respectively, using the SN- UnitData.Request. The Unidata.Request will support the following parameters: Source address, Destination address, Data to be sent, QoS category, Class of Service, Priority, Integrity. The Source and Destination addresses will uniquely identify the Air/Ground router or the aircraft on the AMACS network. The ICAO 27-bit address will be used for the aircraft. The Air/Ground router will have a unique address coded over 3 octets. The maximum data size of each SN-Unitdata.request will be 145 octets. The values allowed for QoS category, Class of Service, Priority and Integrity parameters are defined in Section B For uplink data transmission, the information associated with the Unidata.Request will be sent though a reliable transport network to the GNI from which a join event has been received for the destination address aircraft. The GNI will then handle the received parameters to send the requested information to the destination aircraft, using the required QoS. Handling of the requested QoS parameters is described in Section B The data part of the PDU sent uplink by the GNI will consist of: The local identification of the Air/Ground router; The user data part. The local identification of the Air/Ground router corresponds to a local identifier (from the GNI point of view) that permits unique identification of the Air/Ground router among all the Air/Ground routers connected to the GNI. This identifier has been allocated locally by the GNI and was provided in the Join event triggered by the aircraft. It will permit identification of the data flows exchanged between the Air/Ground router and the airborne router. The GNI will use the received Source address information to find the local identification value to be used. The Destination address will be directly mapped to the corresponding AMACS datalink address. The GNI will implement message queuing mechanisms in order to temporarily store uplink transmission requests until they have been fully completed, i.e. sent and acknowledged at Edition Number: 1.0 Final Page 87

100 the AMACS MAC layer. In the case of failure to transmit the requested information, the GNI will react according to the requested QoS: If a high QoS has been requested (e.g. Guaranteed QoS requested with Deterministic CoS), it will report the transmission error to the A/G router, and the corresponding data packet will be discarded. If a medium QoS has been requested (e.g. Deterministic CoS), re-transmission will be attempted as soon as possible, taking into account potential concurrent requests with higher priority requests arriving in the meantime. The maximum permitted number of retries will be configurable. In case of failure after this number of retries, a transmission error will be reported to the A/G router, and the corresponding data packet will be discarded. If a low QoS has been requested (e.g. Concurrent CoS), re-transmission will be attempted as soon as possible, taking into account potential concurrent requests with higher priority requests arriving in the meantime. The maximum permitted number of retries will be configurable. In case of failure after this number of retries, the data packet will be discarded. When an aircraft receives an uplink PDU, the following information will be provided to the user through the SN-Unitdata.Indication service: Source address, Destination address, User data part. The Destination address will correspond to the sub-network address of the airborne router. It will be locally inserted. The Source address will correspond to the sub-network address of the Air/Ground router. It will be translated from the local identification received in the PDU. For downlink data transmission, the aircraft will send the data part to the GNI through the AMACS Ground Radio Station of the current cell within which it has been inserted. The transmitted PDU sent downlink will consist of: The local identification of the Air/Ground router The user data part. The local identification of the Air/Ground router will be selected, according to the requested Destination address, from the list of available connectivity with Air/Ground routers (notified locally through Join events). Handling of requested QoS parameters will be similar to the GNI behaviour for uplink transmissions, although queuing mechanisms have to deal with a unique sender. When a GNI receives a downlink PDU, it will identify the Air/Ground router to which it will forward the information through the reliable ground transport network. The GNI will translate the received local identification value to the real sub-network address of the Air/Ground router. Based on the datalink interface, it will also identify the sub-network address of the Page 88 Final Edition Number: 1.0

101 Source aircraft. The Air/Ground router will then provide the following information to the user through the SN-Unitdata.Indication service: Source address, Destination address, User data part. The Destination address will correspond to the sub-network address of the Air/Ground router. The Source address will correspond to the sub-network address of the airborne router. As the GNI may be inter-connected with several Air/Ground routers, through several AMACS Ground Radio Stations, it will be able to handle concurrent transmission requests coming from and going to different network entities. B Mobility management This section presents the mechanisms that are used for mobility management, taking into account the above AMACS architecture and protocols stack model. The aircraft AMACS Radio will use geometry information to identify the AMACS cell to which it should request insertion. The monitoring of the associated frequency and the description of the AMACS frame for this cell will allow the AMACS Radio to retrieve information regarding the presence of a ground station and its address, which will be encoded in one slot. When an aircraft first joins a 'user group' (i.e. an AMACS cell), this will result in a Join event being sent to the network user for both the ground A/G router and the airborne router. On the ground side, this will notify the service user that the identified aircraft has joined a 'user group' via the identified Ground Network Interface (GNI). On the air side, this will notify the service user of the GNI address as well as the supported A/G router(s). As the aircraft continues on its flight, a hand-off may take place to another Ground Station. When this occurs, it is signalled to both the airborne and ground users by another Join event. This Join event will identify the new GNI that both air and ground users must now use to communicate. On the airborne side, the Join event will include the following information: the address of the AMACS Ground Radio Station, the sub-network address of the connected Air/Ground router, Local identification of the connected Air/Ground router. The sub-network address of the connected Air/Ground router will permit unique identification of the Air/Ground router on the AMACS network. This value will be coded in three octets. The local identifier of the connected Air/Ground router will permit unique identification of the Air/Ground router from the GNI point of view (local ground reference). This value will be coded in one octet. Edition Number: 1.0 Final Page 89

102 It is noted that the Sub-network address of the GNI will consist of the initial part of the address of the AMACS Ground Radio Station through which the aircraft has been inserted. This will be ensured when deploying AMACS Ground Radio Stations: all such systems connected to the same GNI will have a common address prefix value that will permit unique identification of the connected GNI on the AMACS network. When a GNI is connected to several Air/Ground routers, the airborne system will receive one Join event per connected Air/Ground router. On the ground side, the Join event will include the following information: Sub-network address of the GNI, ICAO 27-bit address of the aircraft. If an aircraft moves from one GNI to another GNI which are both connected to the same Air/Ground router, the second Join event will be identified as a hand-off event. Seen from the points of view of the Airborne router and the Air/Ground routers, there will be two possible simultaneous paths for communication between them. The two paths will be distinguished by the different GNI addresses. Insertion into the new cell will occur before the aircraft leaves the previous cell, permitting the air-ground connectivity to be maintained throughout the flight. When the aircraft leaves a cell, a Leave event will be triggered on both the airborne and the Air/Ground routers. A hand-off between Ground Radio Stations in the same cluster (i.e. connected to the same GNI) will only have a minor impact on both air and ground. On the ground side, the aircraft will be inserted into the next AMACS Ground Radio Station cell and will leave the cell of the previous AMACS Ground Station. The GNI should thus not trigger a Join or Leave event, as routing information from the ATN or IP Air/Ground routers point of view is not impacted (the sub-network address of the GNI and the ICAO 27-bit address of the aircraft have not changed). On the airborne side, the AMACS Radio should recognize that it is still connected to the same GNI (same initial prefix of the address of the AMACS Ground Station Radio) in order to avoid triggering the Leave and Join events. The GNI will handle routing tables in order to identify the list of aircrafts connected and the identification of the AMACS Ground Radio Stations through which each is connected. When two routes exists to reach the same aircraft (handoff situation), the latest one established shall always be preferred. B Quality of Service (QoS) management AMACS QoS management The AMACS system will permit handling of QoS based on four parameters: QoS category Page 90 Final Edition Number: 1.0

103 Priority Class of Service (CoS) Integrity QoS category: this flag will indicate whether the QoS must be provided on a best-effort or a guaranteed basis. From the point of view of the user (pilot or controller), the provision of data link services on a best-effort basis may not be satisfactory. For example, in the case of a trajectory negotiation, it would be better for the user to know that the data link network cannot deliver the requested service in time rather than trying to negotiate another route in a situation which may no longer be optimal. Although QoS shall be handled from an end-to-end viewpoint, the airground link is a potential bottleneck. Priority information will be used to distinguish the relative importance of the exchanged data with respect to gaining access to communications resources and to maintaining the requested QoS. The priority of different message categories has been specified by ICAO in terms of the ATN priority. When AMACS has multiple messages with different ATN priority, but the same AMACS transmit priority, queued to send then it shall take account of the ATN priority in deciding which messages to send first. Table B-2 presents the priority mapping between the types of message category and the ATN network priority. Message category ATN Priority Network/systems management 14 Distress communications 13 Urgent communications 12 High priority flight safety messages 11 Normal priority flight safety messages 10 Meteorological communications 9 Flight regularity communications 8 Aeronautical information service messages 7 Network/systems administration 6 Aeronautical administrative messages 5 Unassigned 4 Urgent priority administrative and UN charter communications 3 High priority administrative and state/government communications Normal priority administrative 1 Low priority administrative 0 2 Edition Number: 1.0 Final Page 91

104 Table B-2 Mapping between message category, ATN priority, and AMACS priority classification AMACS will provide two types of Class of Service (CoS): Deterministic transmission (CoS1) The Deterministic transmission CoS will be used by applications that require a very high level of reliability for the transmission of short messages. Each aircraft will have a dedicated communication channel reserved for sending data at this CoS. This channel shall always be available and maintained by the datalink services. In case of failure to maintain such service, the user will be notified immediately. Concurrent transmission (CoS2) The Concurrent transmission CoS will permit transmission of longer messages, but without a guaranteed delivery time for transmission. Transmission of data at this CoS will be done in a concurrent way between all aircraft in the same cell. All data transmitted using this CoS will be characterized by a priority value. This Class of Service parameter will need to be understood in the context of the requested QoS category. The following table presents the impact of each of them where AMACS will handle a data transmission. Deterministic (CoS1) Concurrent (CoS2) Best Effort QoS requested In the case where there are no guaranteed QoS requests for the current CoS1 slot, then if the transmission fits in a CoS1 slot, transmit the data in the current CoS1 slot. If the transmission is too long for CoS1, then request a slot in CoS2. In case of reception failure (no ACK), then re-transmit the data in CoS2 slots (later in the same frame). In the case where there are guaranteed QoS requests for the current CoS1 slot, then transmit the data in CoS2 slots. Guaranteed QoS requested For the highest priority guaranteed QoS request for the current CoS1 slot, then if the transmission fits in a CoS1 slot, transmit the data in the current CoS1 slot. If the transmission is too long for CoS1, then request a slot in CoS2. In case of reception failure (no ACK), then re-transmit the data in CoS2 slots (later in the same frame). In the case where there are guaranteed higher priority QoS requests for the current CoS1 slot, then transmit the data in CoS2 slots in order of priority. Table B-3 Impact of Class of Service on transmission The integrity parameter will offer the highest level of integrity over the AMACS communication channel. Based on the high level of integrity of the underlying channel, this service will consist of adding a simple CRC as part of the data message exchanged over the AMACS link. This CRC will permit the lowest residual bit error rate to be achieved. It should be noted that independently of the level of service to be provided, whether it is on a best-effort or guaranteed basis, mechanisms should be implemented to monitor the traffic load and usage in each AMACS cell. These mechanisms will allow a better anticipation of the capacity situation, permitting an early reconfiguration of the AMACS cell before capacity problems become a real issue. Page 92 Final Edition Number: 1.0

105 End-to-end QoS management End-to-end communication will involve heterogeneous networks, including mainly an airground AMACS link and a ground transport network. Management of QoS on the AMACS link has been addressed in Section 0. In order to be able to provide end-to-end QoS management between the airborne system and the ground controller system, two alternatives are envisaged: Implementation of QoS management mechanisms on the ground network infrastructure. Solutions based on IP based infrastructure, using IntServ or DiffServ model, are envisaged, Implementation of QoS management mechanisms at the transport level. This transport protocol shall be designed to be used over a network layer that provides best-effort service differentiation (called EDS Equivalent Differentiated Services). This solution has the advantage of providing this information directly to end users in order to decide whether the communication infrastructure is capable of providing the expected QoS. B Standards The AMACS Physical Layer uses features and characteristics of GSM and UAT, for which international standards are available. The AMACS MAC and Data Link layers use features and protocols that have been standardized in VDL Mode 4. Thus while international standards are not yet in place for AMACS, the system is already well specified and the development of the appropriate AMACS standards will be facilitated by the availability of the existing material. B.1.4 Technology Readiness Level (TRL) The system is effectively a collection of COTS components which are well understood and deployed in the commercial marketplace. Standards for these COTS components are available and have been validated in an aeronautical context. A mention of these components is appropriate here: Physical layer (modulation) UAT and GSM MAC layer (access protocols) VDL4 These components have been tested, validated and demonstrated in relevant environments. The choice of components for AMACS is taking advantage of real-life experience gained from actual use of the UAT, GSM and VDL4 systems. However, due to the amount of integration needed, AMACS is judged at TRL level 3. B.1.5 APPLICATION OF TECHNOLOGY TO ATM This section describes the application of the AMACS system to aeronautical communications, which provides the basis for subsequent evaluation. This concept-of-use description involves: Edition Number: 1.0 Final Page 93

106 Concept of operation: description of how the technology is able to operate in the ATM environment. Applicable Frequency Band: the band or bands that are appropriate for the implementation of AMACS for aeronautical communications. Applicable Airspace: the airspace in which AMACS can practically provide aeronautical communications. Services Used and Performance required: the AMACS services that are best applicable to aeronautical communications and meet the required levels of performance. Architecture Integration: description of how the AMACS architecture integrates into the architecture for aeronautical communications. B Concept of operation: cellular deployment Introduction The obvious characteristic of this system which is different from VDL subnetworks is that AMACS requires the aircraft receiver to have an a priori knowledge of ground station positions. In todays VHF ATC and AOC systems, the ground station is implicitly identified by the aircraft through use of a pre-loaded channel map by sector. In other words, the system knows a priori which channel to tune to by virtue of knowledge of the sector being traversed. The AMACS systems use of cellular concepts is somewhat different. With regards to the identified operational scenarios, the AMACS system shall provide a spatial segmentation to take into account the typical message characteristics and requirements for different operational environment. Each cell shall be geographically distinct and will have its own dedicated ground station, which shall use a non-conflicting frequency (as described below). The cell partition will be built on the horizontal geographical plan, but will include vertical segregation as well. Each aircraft shall have knowledge of the parameters of all the cells including the relevant ground station frequencies. A cellular scheme will provide the adequate configuration to the airspace controlled by ATC. The size of the cell should (and could) be modulated according to the traffic. As a first assessment, three operational environments should be distinguished: En-Route Low Density cells, with a range of about the optical range 250NM (for lower airspace of the same type, smaller cells could be used taking into account the line of sight coverage limitations) En-Route High Density cells, with a maximal range of about 100 NM TMA cells, with a range of about 50NM modulated by the size of the airport The cells are tailored to operations, their sizes depending on: air traffic density deployed applications Page 94 Final Edition Number: 1.0

107 en-route, TMA, airport Figure B-8 presents an example of such cellular deployment over the ECAC area. En-route ECAC Periphery 110-NM Radius Cell En-route ECAC Core Area 55-NM Radius Cell Major TMA B Figure B-8 AMACS cell deployment across ECAC Representative C/I derivation and Cellular deployment Application on a 12 frequencies pattern For further refinement of the AMACS system definition, the derivation of the C/I is a very important task. This is not a trivial exercise. As a first approach the C/I can be estimated from the C/N on a channel with AWGN. The degradation caused by a man-made signal, with the same characteristics (modulation, frequency, bandwidth, etc.) on the signal of interest, is smaller than the degradation caused by additive white Gaussian noise. This is because most of the time, the man-made signal is bound (the amplitude is limited, from a receiver point of view). This is not the case for a Gaussian random signal which corrupts the wanted signal. Some measurements on different systems have corroborated this hypothesis. The margin was about 3 db, for PSK systems. Edition Number: 1.0 Final Page 95

108 In order to derive an estimation of C/I from first principles, a cell planning based upon the reuse scheme presented below is considered. Figure B.9 12 frequencies pattern for cell planning With such a frequency plan, the worst-case interference scenario is an air-air interference, which is represented below in Figure B.10. The following paragraphs present an evaluation of the C/I in the co-channel interference case. A cell radius R in the presented pattern is assumed. The distance from the interfered plane to its ground station is the wanted path d w = R. The distance from the interfered plane to its interferer on the same channel is the interfered path d i = 4R. The following propagation model is assumed : A(d) = (constant) + a.10 log(d) where the (constant) term stands for the contribution of frequency and other constant parameters to the attenuation, and a is the exponent applied to the distance. Here, a is assumed to take the value of 2 (free space model) and could range from 3.5 to 4 in ground cellular network. Given these elements, and assuming an omni-directional receiving antenna, if the transmitted powers are kept the same, the C/I at the receiver is simply a function of distance: C/I = A (d i ) A (d w ) = a.10 log(4r/r) C/I = a.6 db, and a 2 thus C/I 12 db The co-channel C/I ratio at the interfered terminal is always better than 12 db with this pattern and these assumptions. However considering the GMSK modulation choice, the GSM FEC rate 260/456 = 0 57 and a very light interleaving, 9 db C/I is considered sufficient. Furthermore, it is assumed here that Page 96 Final Edition Number: 1.0

109 the transmit power of the wanted signal (base station) is the same as the interfering signal (from an aircraft). For these reasons, at least the same performance is expected for the AMACS system. d w =R d i =4R Figure B.10 Co-channel interference in a 12 channels re-use pattern B Applicable Frequency Band and electromagnetic compatibility AMACS systems shall be deployed in the lower L-band ( MHz) which already has an Aeronautical Radio-Navigation allocation. The use of this band is subject to WRC approval of co-prime allocation to AM(R)S. Additionally, a new channelisation scheme will have to be provided in the band, to accommodate the AMACS systems use of channels ranging from 50 khz to 400 khz. One of the key problems for a future communication component that is intended operate in the L-band ( MHz) is co-siting with other radio transmitters that also operate in the L-band. Even if a frequency separation is implemented, to provide some decoupling with other spurious emissions, the robustness of the new communication link will be drastically affected by the proximity of other transmitters on the same aircraft. Therefore the solution is to take advantage of Pulse Blanking Techniques that have been used in many other cases to reduce the effect of strong interference (which is the case on board aircraft due to the very small system isolation). Taking into account that two of the major interferers for the new communication system will be short pulsing transmitters (DME and SSR/Mode S), the duty cycle of the jamming pulses will be lower than that of the AMACS bit duration: the impact of the interference will therefore be limited to a few bits in the frame for which data coding will be the appropriate answer to mitigate the impact of the interference on the frame error rate. Edition Number: 1.0 Final Page 97

110 Such a pulse blanking mechanism has been defined in the UAT standards and will have a common bus interconnecting the avionics elements that could benefit from the information provided (pulse blanking signal whenever a transmitter is on). B.1.6 Airspace Application The use of AMACS systems will provide A/G communications in continental airspace (Core Area as well as periphery), which includes En-route (ENR) and Terminal (TMA) areas. We believe that the surface (APT) area should be covered by another terrestrial-based system (such as WiMax ); oceanic and polar (ORP) communications should be supported by a satellite-based system. B.1.7 ATM services supported AMACS is designed to support distinct modes of operation: The ground-supported mode where the aircraft fly within the range of ground datalink stations (these stations may be interconnected via ground links or not), The autonomous mode where the aircraft fly without any ground datalink infrastructure to support them. Hence AMACS is designed to support all existing and foreseen types of datalink application: o Air-ground and ground-air point-to-point communications (as required today by AOC and also by emerging ATS applications such as COTRAC, ADS and CPDLC), o Air-air, air-ground and ground-air multicast (i.e. locally broadcast) communications (as proposed for ADS-B, FIS-B and TIS-B), o Air-air point-to-point communications (as envisaged for supporting autonomous separation assurance applications). B Proposed Architecture for Technology System Avionics Figure B.11 provides a notional view of the avionics required for an AMACS implementation of ADS-B and AOC and ATS functions. Page 98 Final Edition Number: 1.0

111 Figure B.11 Possible Avionics for AMACS The air-to-air point-to-point connectivity is covered by the ADS-B function. For the air-to-air communication mode (generally supporting surveillance functions such as ASAS and ADS-B), two additional receivers are required in the avionics. While the primary receiver is tuned to the channel associated with the cell within which the aircraft is currently located, the additional receivers are tuned to downstream, adjacent cells to get any necessary signalling information associated with them. B Range The expected range of a typical ground station is 150 NM. The size of each cell is the area of a hexagon with a radius of 150 NM. B Link Budget See Ref 4-1 in section 4.1 for an estimation of the Link Budget for AMACS. B.1.8 Performance Assurance Since even within the ATN framework the AMACS system will be in competition with other services, especially from commercially operated telecommunication systems, our design efforts have been focused at supporting very high performance data link services that will remain unattractive to general purpose telecommunication operators. Both the perspective of a doubling or more of air traffic densities in the most developed countries in the next twenty years and the progressive emergence of the "autonomous aircraft" operational concept will require that a future data link service simultaneously provides a very high integrity, a very high availability, an extremely short fault detection and recovery delay and a short and highly predictable transfer time. It cannot be assumed that the 95% maximum value of the transit time, which is the most usual metric today, will be a sufficiently rigorous specification in the future. Sooner or later, a Edition Number: 1.0 Final Page 99

112 datalink system supposed to address long-term needs yet unable to guarantee a 99% maximum transit time for certain categories of message is bound to become a problem rather than a solution. A high degree of confidence in the provided Quality of Service (QoS) will be required: critical in-flight data communication services for applications such as the ASAS or CPDLC in dense areas will be difficult to certify unless the whole system is designed ab initio with QoS verification in mind. Since relaxing the performance constraints is not really an option, the only cost-effective approach is to incorporate the demonstrability of performance into the very design of the AMACS system, on the one hand, and to avoid to translating the watchword of CNS/ATM integration into a multiplication of common failure modes, on the other hand. AMACS is being designed to meet the COCR requirements for security, continuity, availability and integrity. B.1.9 Status of the technology The AMACS technology solution has been developed from a baseline of the existing UAT/GSM and VDL Mode 4 systems. AMACS has a robust physical layer, with appropriate UAT and GSM specifications which are re-used where appropriate, affording considerable advantage in the costs associated with the development, standardization and fielding of the technology. The GMSK modulation scheme is proven and meets the AMACS requirements. The highperformance MAC layer is based on the existing E-TDMA MAC layer concept. The frame structure is devised to meet the high-qos transmission requirements of AMACS. Existing VDL Mode 4 broadcast and reservation protocols are used. The broadcast experience from VDL Mode 4 is used to take advantage of known operating practices. B.1.10 Status The design of AMACS is finalized at the Physical and MAC layer levels, with complete definitions of the frame, slot and message structures. The error correction coding definition is completed. The Channel structure, cellular deployment and network architecture are specified All of the AMACS message types have been defined and the definition of services has been provided. The protocols and system operations are defined for both point-to-point and broadcast communication Page 100 Final Edition Number: 1.0

113 APPENDIX C. B-AMC TECHNICAL DESCRIPTION C.1.1 Overview A consortium has adapted the B-VHF system for proposed operation in the L-band use and performed investigations to see if and how a possible B-VHF like system can be operated in this band. The high-level system design for this adapted L-band system which is named B- AMC (Broadband Aeronautical Multi-carrier Communications System) is described in this section. The B-AMC A/G sub-system is a multi- application cellular broadband system capable of providing various kinds of Air Traffic Services (ATS) and Airline Operational Communications (AOC) data link services simultaneously. If required, voice A/G channels can be optionally configured. C.1.2 Functional Architecture Airborne B-AMC system offers two modes of operation, one for air-ground (A/G) communications and another one for air-air (A/A) communications. These two modes use different radio channels with different physical layer and DLL approaches. The ground B-AMC system is only required for A/G communications. If a user on ground should participate in A/A communications, a ground A/A terminal similar to these installed on aircraft platforms would be required. In both modes, the B-AMC system in the L-band has to operate alongside with the existing systems (DME, JTIDS, UAT and SSR/Mode S). These systems produce interference towards the B-AMC system and vice versa. The specific interference situation has influenced decisions related to the B-AMC high-level system design. C.1.3 Services Provided & Key Features C.1.4 A/G Communications The A/G mode assumes a star-topology where aircraft within a certain volume of space (the B-VHF cell) are connected to the controlling GS. Each GS provides multiple logical voice and data communications channels to its users by exploiting a dedicated broadband A/G channel. The B-AMC GS is a centralised instance that controls the B-AMC A/G communications. The B-AMC GS can simultaneously support several bi-directional data links with many aircraft. The physical cell coverage is effectively de-coupled from the operational coverage required for a particular voice or data service. Each cell operates in the Frequency-division Duplex (FDD) mode, using its dedicated forward/reverse link (FL/RL) channel pair. As with B-VHF, services requiring wide-area coverage are simply installed at several adjacent B-AMC cells. From the wide-area coverage service point of view, the handover between the involved B- AMC cells is seamless, automatic and fully transparent to the users. Therefore, the B-AMC A/G communications concept is open to the future dynamic airspace management concept. Edition Number: 1.0 Final Page 101

114 The B-AMC system offers a broadcast A/A surveillance link and an addressed (point-to-point) A/A data link with direct air-air connectivity. This mode has not been designed for the B-VHF system and therefore this mode has to be considered for the B-AMC system design. A/A communication between aircraft takes place in a decentralized, self organized way without any need for ground support. For synchronization purposes, the availability of a global time reference is assumed. No A/A voice services are offered by BAMC. The B-AMC system operating in the A/A mode assumes a dedicated global RF resource, the "Common Communications Channel" (CCC). The B-AMC A/A mode uses an Orthogonal Frequency Division Multiplex (OFDM)-based physical layer with completely different parameters (e.g. sub-carrier spacing) than that used for the A/G mode. The target reception range in the A/A mode is 120/200 NM, respectively. The B-AMC A/G sub-system provides bi-directional (FL/RL) Unicast (point-to-point) addressed data links as well as FL multicast and broadcast capabilities with the envisaged capacity [FCS_EVAL] and QoS [COCR] adequate for supporting existing and future ATS and AOC services. The B-AMC data link sub-system can be integrated as an Aeronautical Telecommunication Network (ATN) sub-network and is prepared for IP integration. Other future bi-directional non-atn point-to-point and non-atn broadcast/multicast (FL) data links are supported as well. Some B-AMC cells can be configured as data link (DL) only, but the B-AMC A/G design still supports ATS voice channels (with re-transmission over the GS to re-build the party line functionality) and selective AOC voice communications. When providing voice services, the B-AMC system adopts the B-VHF solution that in turn was based on the VHF Digital Link (VDL) Mode 3 vocoder algorithm. A place for voice packets can be reserved within regularly occurring FL/RL OFDM frames. Although not expected to be widely used, these services may be configured at selected B-AMC cells and used e.g. to provide a certain number of party-line voice channels in regions where VHF channels became fully congested. The B- AMC GS deploys an access arbitration function, which allows a controller s forward link voice transmission to interrupt (pre-empt) always any ongoing re-transmission. Similarly, selective shared AOC voice channels could be installed at some or all B-AMC GSs, leading to a possible withdrawal of VHF AOC channels currently used for similar purposes. The interference situation in the L-band and also the specific propagation conditions require significant modifications of the B-VHF physical layer design. In the B-VHF project, Time-Division Duplex (TDD) was selected to differentiate between forward and reverse link. For the B-AMC A/G sub-system in the L-band, Frequency Division Duplex (FDD) is proposed instead of TDD. It is better aligned with the L-band specific interference picture and can provide increased capacity (one full-size channel is continuously used for the FL, another one for the RL). The maximum currently anticipated channel bandwidth available for the B-AMC FL/RL in the A/G mode is around 500 khz (TBC during the project). Compared to B-VHF, the OFDM sub-carrier spacing is increased from 2 khz in the VHF band to around 10 khz in the L-band to maintain the Doppler robustness at the increased RF carrier frequency. The OFDM symbol duration is correspondingly shortened. Moreover, the OFDM frame duration, spacing and location of pilot symbols for channel estimation as well as the coding/interleaving scheme is adjusted. The concept of TX side-lobe suppression as Page 102 Final Edition Number: 1.0

115 applied for B-VHF is retained within B-AMC to minimize the influence from the B-AMC transmitters towards the DME receivers. The B-VHF OFDMA RL concept is retained for the B-AMC RL. The B-AMC FL is based on OFDMA combined with pure OFDM, instead of MC-CDMA that was used for the B-VHF system. With relaxed voice capacity demands, the OFDM approach offers significant potential for improving the B-VHF A/G data link design. The B-AMC A/G system design includes propagation guard times sufficient for the operation at a maximum distance of 200 nm from the GS. The free space attenuation in the L-band is higher than in the VHF range, but opposite to the B-VHF system, ground antenna beamforming may be well applicable to the L-band, e.g. to provide off-shore coverage with the GS located on-shore. Except for some minor modifications, the B-AMC A/G sub-system inherits the B-VHF system s functional architecture as well as procedures related to system configuration, net initialization, net entry/exit, handovers and resource allocation. C.1.5 Air Interface Description: PHY, MAC & Network The B-AMC A/G data link and A/G voice capability offered by B-AMC strongly rely on the corresponding B-VHF concepts. Like B-VHF, the B-AMC A/G sub-system is a multiapplication cellular broadband system capable of providing various kinds of ATS and AOC voice and data link services simultaneously. In A/G mode, the B-AMC system still supports air-ground party-line voice communications (with re-transmissions via the GS). However, the physical layer (PHY) and Data Link Layer (DLL) are optimized for data link communications. B-AMC has the following key air interface parameters Channel bandwidth: B = 500 khz Length of FFT: Nc = 64 Used sub-carriers: Nc,used = 48 Number of cancellation carriers: Ncc = 2x2 Side-lobe suppression Sub-carrier spacing (500/48 khz): Δf = khz OFDM symbol duration with guard: Tog = 120 µs OFDM symbol duration w/o guard: To = 96 µs Overall guard time duration: g = 24 µs RC-window (roll-off 0.1) for side-lobe suppression 12 µs) Large remaining guard interval (12 µs) OFDM symbols per data frame: N s = 54 The main B-AMC physical layer parameters as given above are the current working assumption which has to be proved in the course of the project using detailed simulations. Special focus during the simulations will be given to the investigation of the co-existence between B-AMC and the legacy L-band systems, like DME and JTIDS/MIDS. The B-AMC framing structure is shown in Figure C-1 below: Edition Number: 1.0 Final Page 103

116 Superframe (240 ms) RA Multiframe 1 (58,32 ms) Multiframe 2 (58,32 ms) Multiframe 3 (58,32 ms) Multiframe 4 (58,32 ms) 6,72 ms RA 1 RA 2 SA DC Data Data Data Data Data Data Data SA DC Data Data Data Data Data Data Data RL BC Data Data Data Data CC Data Data Data Data Data Data Data Data CC Data Data Data Data FL BC Multiframe 1 (58,32 ms) Multiframe 2 (58,32 ms) Multiframe 3 (58,32 ms) Multiframe 4 (58,32 ms) Figure C-1 : B-AMC framing structure As can be seen from the figure above, for both forward link (FL) and reverse link (RL) a superframe of duration 240 ms is subdivided into 4 multiframes of duration ms and a management frame of duration 6.72 ms. For the FL the management frame is a broadcast (BC) frame where general ground station and B-AMC cell information is transmitted. For RL the management frame is configured as random access (RA) slot with two RA opportunities for net entry operation. The multiframe contains 7 (RL) or 8 (FL) data frame for transmission of user data. In addition to data frames, the multiframe contains signalling frames synchronized access (SA) frames, dedicated control (DC) frames, and common control (CC) frames for requesting and granting transmission resources as well as for sending acknowledges. The framing structure is chosen in such a way that voice communication remains optionally configurable. Within each multiframe 3 packets of 20 ms voice, e.g. coming from the vocoder as standardized for VDL Mode 3, can be transmitted. C1.5.1 B-AMC A/A COMMUNICATION B-AMC A/A communication is a decentralized communication. Communication between A/C with in the radio range of each other is enabled ( communication bubble ). All transmissions are based on broadcast transmissions, i.e. transmissions from any A/C can be received by all other A/C within the communication bubble. Addressed communication is realized by packet-switched communication (broadcast & header). To establish the decentralized A/A communication a globally available common control channel (CCC) is used. The foreseen frequency range where this CCC should be located is the range from MHz. For synchronization purposes, it is assumed that a global time reference is available, e.g. based on GPS and/or Galileo. Since it turned out, that it is not possible to develop A/A communications according to all COCR requirements (Version 1.0), several scenarios are currently under investigation. Page 104 Final Edition Number: 1.0

117 As an example, the main B-AMC physical layer parameters for an A/A mode capable to comply with COCR requirements for ADS-B within the ENR service volume (200 nm, 533 ADS B messages per second) are summarized in Table C-1 below: Channel bandwidth B = 2.6 MHz Length of FFT N c = 128 Number of used sub-carriers N c,used = 104 Number of cancellation carriers N cancel = 22 = 4 Sub-carrier spacing Overall OFDM symbol duration Guard interval duration Δ f = 25 khz T = 50 μs og T = 10 μs g Number of OFDM symbols per OFDM frame N s = 7 OFDM frame duration T = 350 μs f Table C-1 : B-AMC physical layer parameters for an A/A The corresponding B-AMC framing structure based on the usage of fixed time-slots is shown in Figure C-2 below: CCC-ENR Frame 1 s Time Slot 1 Time Slot 2 Time Slot 3 Time Slot 625 1,6 ms 350 µs 1,25 ms symbol duration guard time! range > 200 nm!! slots > 533! Figure C-2 : B-AMC framing structure As can be seen from the figure above, with the chosen physical layer parameter setting up to 625 messages, e.g. ADS-B messages, are supported within a frame duration of 1s taking into account guard times for each time slot which enable transmission ranges up to 200 nm. Edition Number: 1.0 Final Page 105

118 A/A communication in remote or oceanic regions might reuse the complete DME spectrum range for additional high-speed point-to-point links. These links are based on the B-AMC A/G mode and might be applied, e.g., for establishing ad-hoc network communications. C.1.6 Standards Although no formal standards are in preparation at the moment however there is a substantial amount of technical information on which standards could be based subject to finalise of the design and validation activity. C.1.7 Technology Readiness Level (TRL) Based on the extensive information supplied B-AMC is assessed at TRL 4. C.1.8 APPLICATION OF TECHNOLOGY TO ATM Concept of Operation B-AMC foresees two modes of operation the air-ground (A/G) mode and the air-air (A/A) mode. For the A/G mode B-AMC inherits the B-VHF capabilities which results in the following characteristics for A/G communications: centralized communication controlled by a ground station (GS); cellular communications concept with B-AMC cell coverage decoupled from service operational coverage (high flexibility); seamless service area and cell handover; data link communication covers broadcast/multicast as well as unicast (point-topoint); voice communication is foreseen and optionally configurable, it covers both selective and party-line voice; B-AMC covers all A/G ATS and AOC services; and B-AMC supports A/G multi-link and multi-service communications. For the A/A mode B-AMC extends the B-VHF capabilities significantly which results in the following characteristics for A/A communications: decentralized direct A/A communication; communication bubbles defined by radio range around aircraft; all A/A communications are based on broadcast transmissions; transmissions from any aircraft can be received by all other aircraft within communication bubble; packet-switched communication (broadcast & header); B-AMC supports A/A surveillance data link (ADS-B); B-AMC supports other A/A data link communication; and B-AMC covers all A/A ATS services (extendable to AOC, APC, and ad hoc net communications). C.1.9 Spectrum Considerations Page 106 Final Edition Number: 1.0

119 The preferable B-AMC L-band deployment is between successive DME channels, i.e. with 500 khz offset to the regular DME channel assignments. Thus, B-AMC is more an inlay than an overlay system. The first approach is to put B-AMC channels between successive DME channels without considering the actual DME channel frequency assignments. However, if mutual interference conditions turn out to be too restrictive, frequency planning can be applied in the sense that B-AMC channels are put between successive DME channels which are not used in the vicinity of the respective B-AMC cell. Moreover, there is the fall back solution of deploying B-AMC within a green L-band spectrum region, e.g MHz or another part of the L-band made available for future aeronautical communication systems. Considerable simulations work has been undertaken on determining compatibility of B-AMC in the L-band. Further work is necessary to confirm the results but early indications are that B-AMC can be deployed within the L-band as an in-lay system between DME channels. However this requires knowledge of the operating frequencies of the DMEs and choice of appropriate channels. This is Option 2 as defined in the study. With these constraints within a B-AMC cell, using QPSK and robust coding techniques, around 270 kbit/s can be achieved. If DME usage is reduced in the future, B-AMC offers much more capacity - up to 1.4 Mb/s. For air/air communication the preferred choice is use of the lower part of the L-band. C.1.10 Airspace Application Based on preliminary performance assessments carried out so far, B-AMC seems able to support applications defined in the COCR in all airspace categories. C.1.11 ATM services supported All data link services defined in the COCR have been assumed in the design of B-AMC. C.1.12 Proposed Architecture for Technology System This section provides an outline of the B-AMC system architecture for the A/G mode. Figure C-3 below provides a block diagram of the deployment of the aircraft and ground elements. Below the figure, Table C-2 contains an explanation of the blocks shown in the diagram. Edition Number: 1.0 Final Page 107

120 Figure C-3 : B-AMC system architecture for the A/G mode Unit Radio Control A_Voice System A_Voice Unit Description Function used by the pilot to interact with B-AMC avionics and to select the desired communications service(s) via an interface (C1). An airborne VCS counterpart, exchanging bi-directional voice and signalling (PTT) with the air B-AMC sub-system over an interface (a3). Airborne vocoding function (conversion between analogue and digital voice). Preferably integrated within an airborne B-AMC radio unit. ATN_Avionics Airborne ATN-capable avionics, interfacing with airborne B- AMC system (ANI) via an interface (a1). It comprises an airborne counterpart (Communications Management Unit, CMU) to the ground ATN BIS as well as airborne data link service processors for ATS and AOC services. Non- ATN_Avionics ANI Airborne non-atn data link avionics, interfacing with airborne B-AMC system (ANI) via interface (a2) and comprising airborne data link service processor(s) for non-atn ATS data link services. Airborne network interface, implementing B-AMC sub-network and DLL protocols, internal management functions and other functions not covered by the B-AMC A_TX/RX block. It provides ATN (a1) and non-atn (a2) external data interfaces. Parts of Page 108 Final Edition Number: 1.0

121 Unit B-AMC A_TX/RX B-AMC Mgmt Description ANI may be delegated to the CMU. Airborne B-AMC transceiver/receiver, comprising MAC and PHY-layer functions and communicating with its ground counterpart, G_TX/RX block, over an air-ground interface (R1). Preferably, it would comprise the A_Voice Unit. Within the B-AMC system itself, there is a distributed internal management function that takes care about all system-internal tasks. GNI provides an interface (g2) for an external B-AMC management client to B-AMC internal management functions. G_Voice System Voice Communications System, exchanging bi-directional voice stream and associated signalling (PTT, SQU) with the ground B-AMC sub-system over an interface (g4). G_Voice Unit Non-ATN DLS ATN BIS B-AMC G_TX/RX GSC GNI Ground vocoding function (conversion between analogue and digital voice). Preferably integrated within GNI, but may be also delegated to the G_Voice system. Ground data link service processor for locally implemented non- ATN ATS data link services. Such services are accessed via an interface (g3). Ground ATN router, using B-AMC as a mobile ATN A/G subnetwork, connected to the GNI over an interface (g1). Ground B-AMC transmitter/receiver, comprising transmitting MAC and PHY-layer functions and communicating with its airborne counterpart, A_TX/RX, over an air-ground interface (R1). Ground station controller, implementing the DLL protocols and functions not covered by the G_TX/RX function. It organises one TX and one RX unit (possibly deployed at separate physical radio sites) into single B-AMC ground radio station and provides local support for B-AMC functions that involve more than one GS. Ground network interface, providing the support for the internal system management and external control over the interface (g2). It interfaces with an external- or internally implements the G_Voice Unit and organises (multiple-) GSCs to provide required services within pre-defined coverage area. Additionally, GNI provides ATN (g1) and non-atn (g3) external data interfaces. Table C-2 : Description of B-AMC system functions C.1.13 Performance Assurance B-AMC has the following features to help assure its performance - robust PHY layer tailored to combat L-band interference; efficient side-lobe suppression to guarantee co-existence; optimized design for data link, but voice remains an option; and minimised delays due to signalling frames. Edition Number: 1.0 Final Page 109

122 C.1.14 Status of the technology Overall, the B-AMC design shows promise as a potential candidate component of the FCI subject to some further work. This includes establishing comprehensive common interference evaluation criteria for all candidate L-band technologies and review the results of the calculations included in the report based on such criteria Completing any design trade-offs to achieve required performance whilst achieving compatibility in the L-band e.g. including interference-adjusted erasure decoding and adding priority handling Investigation of handoffs Security measures such as encryption and authorization Definition of message formats Page 110 Final Edition Number: 1.0

123 APPENDIX D. WCDMA TECHNICAL DESCRIPTION D.1.1 Overview UMTS offers 3G voice and data bearer services, which provide the capability for information transfer mobile users and base stations. It is possible to negotiate and renegotiate the characteristics of a bearer service at session or connection establishment and during ongoing session or connection. Both connection oriented and connectionless services are offered for Point-to-Point and Point-to-Multipoint communication. Bearer services have different QoS parameters depending maximum transfer delay, delay variation and bit error rates needed. 3G supports both dedicated as well as packet data services. As designed data rate ranges are flexible and range from <1 kbps up to 384kbps for R99. Packet data rates of up to 14 Mbps maximum are supported for HSDPA(R5) and 5 Mbps for HSUPA(R7). Modelling work was undertaken to determine the capacity of each technology solution, or more specifically to determine the minimum number of RF carriers (and therefore the amount of spectrum) required in L-band to provide ATC and AOC services to the predicted number and distribution of aircraft operating within European airspace in 2020 and It should also be noted that demonstration flights of a representative UMTS system operating in aeronautical bands were undertaken successfully in Error free datalinks were established at high Doppler speeds and data rates between 9.6 kbps up to 384 kbps were achieved. Flight trials were undertaken in clean spectrum in the VHF and C bands. UMTS offers 3G voice and data bearer services, which provide the capability for information transfer mobile users and base stations. It is possible to negotiate and renegotiate the characteristics of a bearer service at session or connection establishment and during ongoing session or connection. Both connection oriented and connectionless services are offered for Point-to-Point and Point-to-Multipoint communication. Bearer services have different QoS parameters depending maximum transfer delay, delay variation and bit error rates needed. 3G supports both dedicated as well as packet data services. As designed data rate ranges are flexible and range from <1 kbps up to 384kbps for R99. Packet data rates of up to 14 Mbps maximum are supported for HSDPA(R5) and 5 Mbps for HSUPA(R7). Modelling work was undertaken to determine the capacity of each technology solution, or more specifically to determine the minimum number of RF carriers (and therefore the amount of spectrum) required in L-band to provide ATC and AOC services to the predicted number and distribution of aircraft operating within European airspace in 2020 and It should also be noted that demonstration flights of a representative UMTS system operating in aeronautical bands were undertaken successfully in Error free datalinks were established at high Doppler speeds and data rates between 9.6 kbps up to 384 kbps were achieved. Flight trials were undertaken in clean spectrum in the VHF and C bands. D.1.2 Air Interface Description: PHY, MAC & Network The physical layer of the UMTS FDD system is defined in standards section below. The chip rate is 3.84 Mcps. For the reverse link the dedicated channel is divided into two components:- Edition Number: 1.0 Final Page 111

124 Dedicated Physical Data Channel DPDCH This carries the user data information, complete with forward error correction coding, interleaving, etc. Dedicated Physical Control Channel DPCCH This carries the dedicated pilot and power control information. The pilot information allows the Node B (base station) to derive channel estimates to demodulate the DPDCH The DPDCH and DPCCH are transmitted using orthogonal carrier phases. The choice of their relative powers is a complex optimisation. If the DPCCH power is too low relative to the power in the DPDCH then the channel estimates will be poor and the overall power will need to be increased to compensate for degraded receiver performance. On the other hand, if the DPCCH power is too high then it will detract significantly from the remaining power available for transmission of the DPDCH. In general the relative DPCCH power needs to be higher for lower bit rates because the minimum required absolute received power is reduced. When a UE (user equipment) has no data to transmit it can maintain its channel by continuing to transmit the DPCCH and turning the DPDCH off. The effective bit rate of the maintenance channel for UMTS (equivalent to the 1.2 kbps channel for CDMA2000) is then given by the formula DPDCH_Bit _Rate x DPCCH_Power / (DPDCH_Power + DPCCH_Power) D.1.3 Standards WCDMA simulations were based on the following standards Physical channels and mapping of transport channels onto physical channels (FDD) (Release 6), 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, 3GPP TS V6.7.0 ( ) Multiplexing and channel coding (FDD) (Release 6), 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, 3GPP TS V6.7.0 ( ) Spreading and modulation (FDD) (Release 6), 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, 3GPP TS V6.4.0 ( ) Physical layer procedures (FDD) (Release 6), 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, 3GPP TS V6.7.1 ( ) Physical layer - Measurements (FDD) (Release 6), 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, 3GPP TS V6.4.0 ( ) User Equipment (UE) radio transmission and reception (FDD) (Release 6), 3 rd Generation Partnership Project, Technical Specification Group Radio Access Network, 3GPP TS V ( ) Base Station (BS) radio transmission and reception (FDD) (Release 6), 3 rd Generation Partnership Project; Technical Specification Group Radio Access Network, 3GPP TS V ( ) Page 112 Final Edition Number: 1.0

125 D.1.4 Technology Readiness Level (TRL) Although UMTS is widely deployed in its target band for its original application it will require modification for deployment in the L-band (move operating frequency, delete all 3G security implementations and rely on end to end security). Therefore the TRL value is estimated as 5. D.1.5 APPLICATION OF TECHNOLOGY TO ATM Concept of Operation Channels (radio links) are assigned to an aircraft when it enters a radio cell and kept alive for the entire time that an aircraft remains within the cell. This requires multiple scrambling codes are required if the number exceeds 128. DTX is employed at a loading appropriate for achieving the peak and average bit rates required to support the data services. The usage of keep-alive channels is required. Two antenna base stations are to be employed. The use of two antennas provide coherent gain against interference. In the aeronautical environment there is no additional diversity gain because the channel is substantially non-fading. A random scheduler is employed. Thus the activity on the channel is assumed to be random. Hard Handover with a low hysteresis is employed rather than Soft handover. Spectrum Considerations In the study [Ref 8-2 in section 8] it was concluded that the operation of the new UMTS air to ground communication link in the L-band may be possible if protection measures identified in the study are introduced. The issue of in-band interference into the co-sited airborne DME receivers remains a concern, as airborne UMTS transmissions operating in continuous mode can potentially desensitise the co-sited DME receiver front end. However, it is expected that this conclusion would apply to any continuously transmitting communication system operating in the band. UMTS standards also include compressed mode of operation (gating or DTX discontinuous transmission) which could be connected to the L band suppression bus. Though all compressed mode parameter are available no effort has been done so far to test co-sited DME compatibility under these conditions. Deployment of this WCDMA technology would require two cleared 5MHz bands in the lower and upper parts of the L-band. While 5MHz unused spectrum is available around 968 MHz, in the upper L band 1 TACAN (64X) is located around 1149MHz where the Uplink is supposed to be located. Although guard band requirements have never been studied it is possible that another 32 DME channels need to be reassigned in case 5 MHz spectrum needs to be cleared at either side of the UMTS Uplink. Due to the pressure in the DME band and the expected growth in DMEs in Europe obtaining such cleared portions will be very difficult. Edition Number: 1.0 Final Page 113

126 Airspace Application The WCDMA (UMTS 3G) implementation considered will require a comprehensive 3G-type infrastructure and a cellular deployment with cell diameters of 160 NMs for enroute and smaller cells for airport and TMA coverage. Ground infrastructure cost is considered high when taking into account all 3G security measures (such as data encryption, authentication and use of SIM cards) as well as access to a switched network for voice operation. When going for a full IP implementation on packet data the number of base stations needed is very close to the amount of airports handling revenue flights. WCDMA is expected to be deployed in a similar manner to current VHF ground stations. Consequently it is expected that the same number of WCDMA sites will be required as current VHF stations. ATM services supported The performance assessment undertaken was based on an early version of the COCR. The values for capacity assessment were based on a propriety simulation model which reinterpreted the COCR requirements resulting in a need of an average data rate throughput of 1k bps per aircraft with peak data rates of 9.6 kbps in order to achieve the latency requirements. All simulations took place considering dedicated datalinks between aircraft and ground station based on Release 99 only (in line with the 2002 flight trials). In order to obtain objective spectrum need requirements all simulations included interference from 1 st, 2 nd and 3rd cell rings around the investigated cell. A summary of the results were - In the forward direction a single UMTS channel (2x5MHz) provides adequate capacity for the worst-case minute according to the SAAM data for 2020 and 2025, in both London and Switzerland. In the reverse direction, a single UMTS channel (2x5 MHz) provides adequate capacity for the worst-case minute according to the SAAM data for 2020 and 2025, in both London and Switzerland. The simulation also shows that a packet data link is preferred instead of establishing dedicated data links between ground and each aircraft individually although this was not tested. Status of the technology WCDMA technologies are becoming widespread in commercial services and are the basis for 3G mobile phones, etc. They have inherent benefits in terms of efficient use of spectrum and cellular capacity. However it seems that compatibility within the target band the L- band will mean these advantages will not be able to be realised by aviation. Page 114 Final Edition Number: 1.0

127 APPENDIX E. PROJECT 34 TECHNICAL DESCRIPTION E.1.1 Overview P34 is a wideband Public Safety digital radio system that provides high-speed packet data services using the Internet Protocol on 50, 100, and 150 khz channels in the 700 MHz band. P34 systems provide connectivity between Mobile Radios and Fixed Network Equipment (FNE), Mobile Radios to Repeaters to Mobile Radios, and direct Radio to Radio (either mobile or fixed) connectivity. The objectives stated in the Project 25/34 (the official name of P34 was Project 25/34) Statement of Requirements (SOR) are: establish, from the user s perspective, a standards profile for the operation and functionality of new aeronautical and terrestrial wireless digital wideband public safety radio standards that can be used for the transmission and reception of voice, video, and high speed data in a ubiquitous, wide-area, multiple agency network. Some of the primary attributes of this network(s) would include, but not be limited to, the following: B. Affords immediate, significant and evolutionary improvements in radio bandwidth and spectrum efficiency. F. Establishes a digital tactical communications architecture that provides for a migration-in place transition within existing systems, effected through full backward interoperability/compatibility with existing analogue and digital wireless communications systems used by local, state and federal agencies. G. Is consistent with Project 25 Phase I and Phase II and parallel federal standards. I. Allows for the half and/or full duplex transmission of digital information at gross channel data rates of up to a minimum of megabits per second (Mb/s, 3rd generation), and 155 Mbits/s or higher for 4th generation technologies. J. Allows for the seamless hand off of subscriber units moving between fixed sites. K. Allow for multiple levels of security, network integrity, and availability Project 34 is standardised through the EIA and offers addressed wideband aeronautical and terrestrial mobile digital radio technology standards for the wireless transport of rateintensive information. The project committee discovered four generally universal limitations restricting the use of commercial services for mission-critical public safety wireless applications: Priority access and system restoration Reliability Ubiquitous coverage Security P34 describes a platform that can be installed as a government/ commercial partnership that overcomes these limitations and provides universal access to all subscribers within a carefully controlled and managed network. It establishes standards for the transmission and reception of voice, video and high-speed data in a wide-area, multiple-agency network. Edition Number: 1.0 Final Page 115

128 The P34 system is defined with open, standardised interfaces, so that manufacturers equipment can be interoperable. It is the intent of the P34 specification that a system may be implemented where the equipment on either side of any open interface may be supplied by any manufacturer. The three open interfaces that are defined are the: Wideband Air Interface (U W ) Data Peripheral Interface (Mobile Data Peripheral to Mobile Radio Control, A W ) Data Interface (Radio Frequency Gateway to Data End System, E W ) A depiction of the P34 open system architecture is shown in Figure E-1 below. E.1.2 Functional Architecture Figure E-1 Functional Architecture of P34 The functional groups defined for Project 34 include the mobile radio, mobile routing and control, mobile data peripheral, base radio, base routing and control and radio frequency gateway. E.1.3 Services Provided & Key Features The P34 system is specified to provide IPv4 and IPv6 bearer services for the transport of packet data using the IP suite of protocols. The wideband IPv4 (and IPv6) delivery service is required to directly support standard IP transport layers, including UDP, TCP and RTP. It may optionally transport other protocols via standard IETF encapsulation methods. Unicast service is required, and broadcast and multicast services are standard options. Utilisation of Mobile IP and IPsec services may be optionally implemented. Page 116 Final Edition Number: 1.0

129 The P34 supplemental services include security, data compression, streaming audio transport and streaming video transport. The following descriptions of these services apply: Security: The wideband data suite should include capabilities for packet integrity, confidentiality and User/radio authentication Data Compression: The wideband data suite should include capabilities for both IP header and user data compression. Streaming Audio Transport: The wideband data suite should include capabilities for standard Internet streaming audio services. Streaming Video Transport: The wideband data suite should include capabilities for standard Internet streaming video services. E.1.4 Air Interface Description: PHY, MAC & Network Figure E-2 below shows the P34 air and data interfaces for the mobile radio to fixed network equipment configuration. The air interface is precisely the same in the direct (mobile radio to mobile radio) mode, and consists of an IP network layer over the layer 2 and layer 1 common air interface for data transport. P34 has two defined physical layers. One is required (Scalable Adaptive Modulation, SAM) for interoperability, whereas the optional physical layer (Isotropic Orthogonal Transform Algorithm, IOTA) is provided for increased capacity. Both physical layers define adaptive signal constellations on an Orthogonal Frequency Division Multiplexed (OFDM) set of carriers. SAM uses QPSK, 16QAM or 64QAM as channel conditions warrant. IOTA uses an Amplitude Shift Keyed modulation format, with 2-ASK, 4-ASK and 8-ASK signal constellations. Both physical layers are defined with a base implementation on a 50 khz channel, using modulation parameters and frames that simply scale to provide the required 100 and 150 khz channel bandwidths. Table E-1 shows the modulation parameters for SAM. Clearly, all of the parameters stay the same, with the notable exception of the number of RF carriers (called subchannels in the table), which scales. This provides a very robust mechanism whereby the time domain frame is also scaled by repetition (the same basic structure is used once in the 50 khz system, twice in the 100 khz and three times in the 150 khz) and the extra bits are now mapped to the extra carriers. Edition Number: 1.0 Final Page 117

130 Figure E-2 : P34 Radio to Fixed Network Equipment Reference and Protocol Models Table E-15-1 Scalable Adaptive Modulation Parameters Page 118 Final Edition Number: 1.0

131 The expected performance of this modulation in the A/G channel is quite good. Rather than using the typical cyclic prefix that is common to most OFDM systems, both SAM and IOTA implement coherent detection by transmitting a number of pilot symbols in every frame. Each pilot symbol transmits a known phase and amplitude value to the receiver. From this, the receiver can determine the amplitude and phase distortion of the channel, and apply the inverse function to reconstruct the symbol. This technique provides immunity to delay spread as long as the coherence time of the channel is long compared to the symbol duration. An estimate of channel coherence time can be formulated from the Doppler spread of the channel (they are inversely proportional). The Doppler spread associated with the A/G communications channel can be estimated and compared to the symbol rate, to judge the immunity of this waveform to Doppler spread. Before discussing this however, it is illustrative to recall the assumptions used to create the classic Jakes Doppler power spectrum. The derivation of the spectrum assumes envelope detection and a uniform distribution of azimuthal angles of arrival. This latter assumption provides a nice approximation for an urban canyon; however, it isn t likely that an aircraft in flight would have angles of arrival that came anywhere near this approximation. Most authors in describing the A/G channel use a two-ray model. Such a model has a bimodal Doppler distribution. Regardless, the worst-case assumption of uniform angles of arrivals results in some useful approximations that can be made about the Doppler spread that is expected for the A/G channel. In a study conducted for EUROCONTROL, investigations into the feasibility of UMTS for Air Traffic Control focused on modelling the small-scale fading effects of the A/G channel. The following observations can be drawn from the simulations: As the Rician K factor increases, the RMS Doppler spread decreases. This effect is significant, since the Doppler spread decreases by half of its maximum value when K goes from 10 db to 0 db. The Doppler spread is very small at large distance from the airport, and increases as the plane enters in the scattering circle. Again, it is expected that the model largely over-estimates this effect. As the plane gets closer to the airport, the RMS Doppler spread decreases, since the LOS component received by the airport antenna is mostly dominant. Finally, the impact of the Doppler spread at VHF is extremely small compared with the computed Doppler spread at C band. For instance, the maximum RMS Doppler spread at VHF is about 40 Hz, as compared to 1,500 Hz at C band with K= 10 db. Nevertheless, the maximum computed RMS Doppler spread is about 700 Hz for a Rician K factor equal or above 0 db in C band and decreases to less than 250 Hz if K = 10 db. The P34 signalling rate of 4800 symbols/second is sufficiently high that the Doppler spread predicted for the A/G channel should not be an issue. Were this not the case, or if the Doppler spread is somehow larger than we might expect, significant work has been done to characterise the effects on OFDM, and most authors report that the effect of large Doppler Spread on an OFDM system is proportional to the number of carriers in that system. Since the P34 physical layer uses a maximum of 24 carriers (as compared to hundreds or even thousands in other OFDM systems) P34 should be fairly robust to intercarrier interference that is caused by large Doppler spreads. A useful result of an analysis of OFDM is quoted below: Edition Number: 1.0 Final Page 119

132 In this paper, we have first investigated the effect of the number of carriers (N) and the guard time duration (υ) on the performance of an OFDM system operating on a frequency selective time selective fading channel. Our main conclusions are the following. For short frames, the time-selectivity of the channel can be ignored. The frequency-selectivity of the channel yields equal portions of ISI and ICI. The total interference power decreases with υ and is proportional to 1/N. For long frames, the frequency-selectivity of the channel can be ignored. The time-selectivity of the channel yields ICI but no ISI. The ICI power does not depend on υ and increases with N. The P34 MAC provides the following functions: Logical channel management and synchronization o Random Access Channel o Broadcast Control Channel o Slot Signalling Channel o Packet Data Channel Channel access, allocation of bandwidth, and contention resolution o Priority queuing o Slotted-Aloha reservation requests o Carrier sense multiple access for direct mode (mobile to mobile) o Dynamic radio link adaptation control o Radio power management Uses both closed and open-loop power control o Radio channel encryption and scrambling The P34 MAC layer priority queuing and slotted Aloha reservation request functions are accommodated via inbound random access slot structures. This slot structure limits the design range of a P34 system to km for SAM and 150 km for IOTA. However, the design range would appear to be easy to modify by requiring that only the even (or odd) reservation slots be used when making reservation requests for data. The P34 standard defines three slot structures: Outbound continuous stream of 10 ms slots Random Access Inbound 500 μs guard and 500 μs ramp-down for IOTA, 625 μs guard and μs ramp-down for SAM Scheduled Inbound 0 μs guard and 500 μs ramp-down for IOTA, μs guard and μs ramp-down for SAM The P34 MAC layer implements a timing advance that assures propagation delays are not seen at the radio receiver except for the initial random access slot. Figure E-3 shows the P34 slot structure. Each standard 10ms slot is partitioned into two random access data slots (note that a 50 khz system has only one frame or slot structure, whereas the 100 khz system has two, and the 150 khz system has the three slot structure that is shown in the figure). The figure is colour coded to show the notional increase in guard band that could be provided if only the even reservation slots were allowed to be used (coloured green) and the odd slots (coloured red) were not utilised. (Note that the drawing is not to scale.) Page 120 Final Edition Number: 1.0

133 Figure E-3 : P34 Slot Structure (150 khz System shown) E.1.5 Standards The P34 standards are complete, with the exception of TIA-902.AAAB (Text Messaging Service), which is still in drafting, and TIA-902.CBAA (IOTA Transceiver Method of Measurement) and TIA-902.CBAB (IOTA Transceiver Performance Recommendation) which are also still in drafting. The SAM modulation is completely specified with published specifications for the physical layer, the MAC, link layer control and mobility management, as well as the method of measurement and transceiver performance standards. Figure shows the status of the P34 standards. Figure E-4 : P34 Standards Status E.1.6 Technology Readiness Level (TRL) Although the use of P34 (TIA-902) for aviation purposes could benefit from the COTS development it will require modification to operate in a new band and may involve some modification of the physical layer. Consequently it is assessed at TRL 3. Edition Number: 1.0 Final Page 121

134 E.1.7 APPLICATION OF TECHNOLOGY TO ATM E.1.8 Concept of Operation This section describes the application of Project 34 to aeronautical communications, which provides the basis for subsequent evaluation. This concept of use description involves the following elements: Applicable Frequency Band: the band or bands that are appropriate for the implementation of Project 34 for aeronautical communications Applicable Airspace: the airspace in which Project 34 can practically provide aeronautical communications Services Used: the Project 34 services that are best applicable to aeronautical communications Architecture Integration: description of how the Project 34 architecture integrates into the architecture for aeronautical communications. E.1.9 Concept of use Some modifications to the P34 standards would be required to accommodate the long ranges required for A/G communications. Current P34 specifications would accommodate sectors up to km in extent. Modifications to the channel random access protocol seem straightforward, and would enable the provisioning of large sectors. E.1.10 Spectrum Considerations P34 systems could be deployed in the DME band (960 to 1164 MHz) which already has an Aeronautical Radio-navigation allocation. Use of this band would be subject to WRC approval of co-prime allocation to AM(R)S. Additionally, a new channelization scheme would have to be provided in the band, to accommodate the P34 system s use of 50, 100, and 150 khz channels. In this scheme the P34 base stations would be full-duplex and the mobile radios would operate in a half-duplex mode. Communications between the aircraft (mobile radios) and the ground (base stations, or more precisely fixed network equipment) would follow the P34 Mobile Radio to Fixed Network Equipment process. Communications between aircraft would be in accordance with the P34 Radio to Radio configuration. This is the most basic of P34 configurations, and is frequently called talk-around in the literature. Both modes would be supported by the same avionics radio. E.1.11 Airspace Application The use of P34 systems would provide A/G communications in continental airspace, which includes enroute, terminal and surface communications, but excludes oceanic and polar communications. Additionally, air-to-air communications would be provided in all regions by these technologies. The Aeronautical Communications Services that could be provided by P34 include: Pilot-Controller Voice: group conference, addressed, and broadcast A/G and G/A addressed data Page 122 Final Edition Number: 1.0

135 G/A broadcast data Direct A/A communications P34 is a packet data protocol. Voice transport over P34 would necessitate the use of Voice over Internet Protocol (VoIP). Talk groups would be set up using multicast IP services, and individual voice calls would be set up using Unicast IP services. Most of the voice requirements could be met by P34, even though its primary intent was for delivery of highspeed data. Air-to-air data services and ground-to-air data services are native modes of the technology. Provisioning ADS-B with P34 would be somewhat problematic because of the size of the P34 random access slot. P34 defines a random access slot of 5 ms duration. This means that a 50 khz P34 system could provide no more than 200 random access opportunities for broadcast of ADS-B position reports a second. Each slot provides 262 bits of useable (payload) data, as the specification requires that the random access slots use the lowest modulation symbol constellation (the IOTA physical would thus use 2-ASK and provide 262 bits; SAM uses QPSK and provides somewhat less, roughly 164 bits). When compared with the UAT, which offers 3200 message start opportunities every second, each providing the ability to send either a 16 or 32 byte ADS-B message, the following observations can be made: IOTA physical layer looks like a better match than the SAM physical layer for transfer of ADS-B message (provides the same data message transport size as UAT) In order to provide the same number of message opportunities, the P34 system would have to be scaled sixteen-fold. This represents a system with a signal bandwidth of (16*50 khz) 800 khz, which compares favourably with the UAT As the modulation is defined to scale linearly, this seems to be achievable. However, this signal would require a large number of subcarriers (roughly 397 for IOTA and 128 for SAM), and its performance in the A/G channel needs to be evaluated carefully. E.1.12 ATM services supported The P34 services that would be used to provide A/G communications include: Unicast IPv4 and IPv6 Broadcast IPv4 and IPv6 Multicast IPv4 and IPv6 Security Services Mobility Management These can support A/G Addressed, A/G Broadcast, A/A Addressed, A/A Broadcast communications. E.1.13 Proposed Architecture for Technology System Figure E- 5 provides a notional view of the avionics required for a P34 implementation of ADS-B and AOC and ATS functions. Since the P34 network layer is IP, implementation of most of the switching, control, mobility management and security functions could be accomplished with commercially available routers. Edition Number: 1.0 Final Page 123

136 Figure E-5 : Possible avionics for P34 E.1.14 Status of the technology The P34 (TIA-902) standards appear to have many features required for aviation safety communications and can meet the requirements for ATS and AOC at least in en-route airspace. P34 (TIA-902), assuming that the spectrum compatibility issues can be resolved, has the potential to be used as the basis for an aviation L-band system at lower risk through use of non-cots development. Page 124 Final Edition Number: 1.0

137 APPENDIX F. LDL TECHNICAL DESCRIPTION F.1.1 Overview The L-Band Data Link (LDL) candidate is essentially the VDL Mode-3 technology specification band-shifted and with a re-designed physical layer for L-Band operation. This technology is classified as part of the custom broadband technology family. This family includes a range of broadband technology specifications with potential applicability to aeronautical communications. A subset of these technologies, including LDL, is being specifically designed for aviation. While the proposed VDL3 technology was considered for implementation in a manner similar to the current aeronautical radio architecture (e.g. a host of radio of radios throughout the NAS providing sector-based coverage), the proposed concept for LDL is the implementation of a regular grid of radio sites. F.1.2 Air Interface Description: PHY, MAC & Network While the upper layer protocols of the proposed LDL technology are almost identical to VDL3, the physical layer has been re-defined to accommodate operations in L-band. A summary of the proposed parameters (and a comparison to VDL3 parameter values) is provided in the Figure F-1 below. Figure F-1 : Overview of LDL Physical Layer Parameters The LDL proposal accommodates a range of voice and data communication services. These are offered using a five slot TDMA frame structure, where each frame is 120 ms in duration. The selected application mode of LDL for FRS data communications is the 5T configuration. This configuration is compared and contrasted with other configurations in Figure F-2 below. Edition Number: 1.0 Final Page 125

138 Figure F-2 : LDL Voice and data configurations F.1.3 Standards LDL is a modification of VDLM3 for which ICAO SARPs have been developed. New standards will be required for LDL. F.1.4 Technology Readiness Level (TRL) This technology is evaluated as TRL level 3. F.1.5 APPLICATION OF TECHNOLOGY TO ATM Airspace Application LDL is targeted at TMA and en-route continental airspace. ATM services supported Voice and data services can be accommodated. It is envisaged that the initial design would be aimed at a data only mode using the 5T arrangement. Status of the technology As reflected in the TRL level 3 as LDL is at the concept stage and further work would be required to confirm design choices. Page 126 Final Edition Number: 1.0

139 APPENDIX G. INMARSAT SWIFTBROADBAND TECHNICAL DESCRIPTION G.1.1 Overview Inmarsat s Broadband Global Area Network (BGAN) provides always-on Internet Protocol services, telephony and ISDN for land, maritime and air mobile users. The aeronautical service supported by BGAN is SwiftBroadband. BGAN uses the Inmarsat-4 (I4) satellites and a new generation of user equipment BGAN to deliver higher data rates and lower costs than previous Inmarsat systems. BGAN is very flexible and is consequently complex to understand. This annex gives a high level description of the BGAN method of operation. G.1.2 Functional Architecture BGAN User Equipment, (UE), offer communications through a microwave link anywhere with a line-of-sight to one of the Inmarsat-4 (I-4) geostationary satellites. An I-4 satellite relays traffic between the UEs and the Satellite Access Stations (SAS). An SAS is a BGAN Earth Station - of which there are currently two one at Burum in the Netherlands and the other at Fucino in Italy see Figure G-1 below. The SAS houses the Radio Network Controller (RNC) and the Core Network. The RNC manages the radio traffic to and from the satellite whereas the Core Network provides the terrestrial telecommunications infrastructure and switching. All traffic passes through the RNC and Core Network where it is interconnected with private IP networks, the Internet or the public telephone network. Figure G 1 : BGAN Ground Infrastructure to support 4F1 and 4F2 satellites An I-4 satellite communicates with the AES using spectrum in the L-band. The I4 satellite subdivides its L-band spectrum into a total of approximately 600 channels in the forward Edition Number: 1.0 Final Page 127

140 (RNC to AES) direction and the same number in the return (from AES to RNC) direction. Each channel (also referred to as a slot or sub-band ) is 200 khz wide. Coverage is illustrated in Figure G-2 below. This shows three satellite coverage areas but currently only two satellites have been launched. Figure G- 2 Proposed SwiftBroadband coverage (three I-4 satellites) 2 BGAN maximises the use of this satellite capacity by reallocating it dynamically to meet demand, to ensure that bandwidth is always available when and where users need it. This paper describes how this is achieved. G.1.3 Services Provided & Key Features The following services (Table G-1) are implemented in the current BGAN network. The range of services that BGAN provides is expanding so this list will change. 2 This map depicts Inmarsat s expectation of coverage but does not represent a guarantee of service. The availability of service at the edge of coverage areas fluctuates depending upon conditions. The launch of the F3 satellite will be determined in due course. Page 128 Final Edition Number: 1.0

141 Table G-1 : Current Services Supported by Land BGAN N.B.: 1. Packet loss ratios are for small packets (e.g. VoIP) via land portable terminals 2. Interactive class may be considered for support in the future Circuit Switched Services BGAN currently supports two types of circuit-switched, fixed bit rate services: 4 kb/s Telephony 64 kb/s ISDN Voice calls are compressed for transmission over the satellite. BGAN uses a DVSI Inc. developed AMBE+2 codec, which compresses speech at 4 kb/s (i.e. 1/16th of the capacity required in a terrestrial telephone network but with near identical audio quality). The AMBE+2 codec is a voice codec only, it will not pass analogue modem or fax data nor will it work with cryptographic equipment. The larger BGAN AESs (UE Class 6 and 7) support a 64 kb/s ISDN channel which can be used for data or for 3.1 khz audio (e.g. a user needs to transmit analogue modem or fax data or use a cryptographic encoder). The BGAN network itself does not compress data on the 64 kb/s ISDN traffic, although this can be done externally. Packet Switched Services BGAN currently supports fixed rate and variable bit rate IPv4 services: Background Class A variable bit rate IP service. Capacity is allocated dynamically by the network on the basis of the user s demand, the user s current link quality and the competing demands of other users sharing the same channel. Users are typically charged on the basis of data transmitted and received rather than duration of connection. The background class connection provides reliable in-order delivery over the satellite (i.e. any data lost due to random errors on the radio link is automatically retransmitted and re-ordered). Edition Number: 1.0 Final Page 129

142 Interactive Class A variable bit rate IP service with reliable in-order delivery like the background class but where the user s subscribed capabilities permit prioritisation over other users of variable bit rate capacity. Streaming Class (reliable) A fixed bit rate IP service with reliable in-order delivery where the user sets the bit rate at the start of the connection and this rate is fixed for the duration. Users of streaming class are typically billed by duration not data sent/received since satellite capacity is reserved whether the capacity is used or not. Streaming Class (unreliable) A fixed bit rate IP service similar to Streaming Class (reliable) but with no attempt to retransmit data lost over the satellite link. This class is designed for real-time applications that benefit from low delay variations but can tolerate a higher errorrate. G Spot Beam Hierarchy The I-4 satellite increases the total channel capacity by means of frequency reuse. By subdividing the coverage into different beams, the same channel frequencies can be reused many times. The same frequencies cannot be used in overlapping beams to avoid interference but where beams are spatially separated frequency reuse is used extensively. Beams serving a wide coverage area offer lower data rates and less frequency reuse. Beams serving a concentrated coverage area offer high data rates and high frequency reuse. Each I-4 satellite provides the following beams: A single global beam covering the whole satellite field of view. 19 regional beams arranged on top of the global beam, covering the whole satellite field-of-view. 228 narrow beams arranged on top of the regional beams, covering the whole satellite field-of-view. This is illustrated in Figure G-3 below. Page 130 Final Edition Number: 1.0

143 Figure G- 3 - BGAN Satellite Beam Hierarchy and Functions In BGAN the different beams serve the following purposes: The global beam is used in the forward direction exclusively. It transmits a carrier that all terminals tune to immediately at switch-on for pointing purposes and to receive a broadcast of system information including the map of the regional beams and the carrier frequencies in each of those beams. Once a terminal has successfully received the global beam system information it retunes to the regional beam that serves its location. Each of the 19 regional beams has forward direction carriers which send additional broadcast system information and paging messages to terminals in that beam. At least one channel per regional beam will be allocated in the return direction to allow terminals to register onto the BGAN network and send system signalling. Only signalling (i.e. no voice or data) is transmitted on the regional beams (SMS is counted as signalling and can be sent in the regional beams). UEs that are registered with the BGAN network and are idle will tune to the regional beam forward bearer and await paging messages for incoming calls or IP packets. The narrow beams are used for traffic (i.e. voice, ISDN or IP). When a UE initiates or receives traffic it is instructed to hand over from the regional beam to receive a carrier in the narrow beam that serves its location. When traffic for that UE ends, it Edition Number: 1.0 Final Page 131

144 is handed back to listen to a regional beam carrier. Forward and return direction carriers in the narrow beams are dynamically activated and withdrawn as required. When a UE terminates its last traffic connections in a narrow beam it is immediately handed back to a regional beam. The RNC will also time out a variable bit rate connection if no packets are exchanged for a period and hand the UE back to the regional beam. If any packets subsequently arrive at the UE or the RNC for this connection then the UE is immediately handed back to the narrow beam and the connection is restored, ready to exchange traffic. G.1.4 Air Interface Description: PHY, MAC & Network The BGAN air interface supports a matrix of carriers and bursts of different modulation type, symbol rate and code rate. In BGAN terminology carriers and bursts are known collectively as bearers. The following description presents the configuration of BGAN bearers correct as of Q G Forward Direction (to UE) Forward Direction Bearer Types The BGAN air interface offers a range of forward direction bearers. For each type of beam (global, regional, narrow) Inmarsat has selected appropriate forward direction bearers. Table G-2 shows the bearer types used in the forward direction. Table G-2 : Forward Direction Bearer Types currently used in BGAN A forward direction bearer is a carrier transmitting a continuous stream of 80 ms data frames at constant power. Each of the 80 ms frames consists of one, four or eight blocks of data ( FEC blocks ) each separately turbo-coded. Each 80 ms frame is preceded by a unique-word pattern. A single forward bearer type has been chosen for use in the global beam. This bearer has a bandwidth of 10.5 khz, uses QPSK modulation (2 bits per symbol) and has a symbol rate of 8.4 ksym/s. There are two choices of forward bearer in the regional beam. The AES will use the highest rate channel it can for the current link conditions. Page 132 Final Edition Number: 1.0

145 A single forward bearer type has been chosen for use in the narrow beam. This bearer has a bandwidth of 189 khz and uses 16 QAM modulation with a symbol rate of 151 ksym/s. In the regional and narrow beams the data rate achievable is variable G.1.5 Standards BGAN and SwiftBroadband specific services are defined in an Inmarsat System Definition Manual. This is not generally available except to partners developing equipment or services to use BGAN. G.1.6 Technology Readiness Level (TRL) The TRL level for SBB to support safety related communications i.e. ATS is 7. This is based on the availability of the SBB for aeronautical non-safety related but without the implementation of technical enhancements to meet the needs of ATS. G.1.7 APPLICATION OF TECHNOLOGY TO ATM Concept of Operation Currently SBB is not designed to support ATS communications. If it were a similar service distribution arrangement would be expected as with the existing Inmarsat Classic Aero service i.e. ATS would get access to the service via communication service provider. Spectrum Considerations SBB operates in the MSS band. Airspace Application The airspace potentially applicable to SBB is that within coverage (approx +/- 78 degs N/S) for which it can meet requirements. This is not yet known. Status of the technology SBB has potential in the short to medium term to support safety related communications if some additional features such as priority and pre-emption were provided. In additional the lifetime of the satellites that supports BGAN/SBB will be reaching the end of the life around Consequently SBB is not considered as a viable component of the future communication infrastructure. Edition Number: 1.0 Final Page 133

146 APPENDIX H. ESA ATM SATCOM TECHNICAL DESCRIPTION H.1.1 Overview The ESA ATM SATCOM system can be defined as a modernised version of the ICAO Classic Aero Satcom System (or AMSS), which has been now in operation for more than 15 years. ATM SATCOM reuses some concepts of the AMSS, such as reliance on geostationary satellites, while overcoming the legacy system limitations with the aim to support future ATM mobile communication services with the required performance level. Alike legacy AMSS, the ATM SATCOM model is characterised by: 1. Interoperable Standard supporting Multiple Service provider scheme, 2. Operation in protected radio-spectrum allocation for safety and regularity of flights 3, 3. Geostationary Satellite Communication system, 4. Ground to Air connectivity supporting ATM services. In addition, ATM SATCOM offers lighter airborne equipment than AMSS, while providing a more reliable service, and a better usage of available spectrum. Improved performance results from the integration of state-of-the-art satellite communication technology into the new system: Improved Quality of Service : better availability and integrity performance through implementation of QoS mechanisms, Light Terminals : minimal antenna size and drag, reduced transceiver size and weight Improved Spectrum Efficiency : latest channel coding and access techniques, Thanks to the improved efficiency brought by ATM SATCOM at service and terminal levels (passive omni-directional antenna, passive cooled HPA), equipment cost is lower. With the reduction of volume and power required for airborne equipment, usage of satellite services will therefore no longer be limited to long haul commercial aircraft and high end corporate aviation, but will also become affordable to single aisle commercial aircraft and general IFR aviation. H.1.2 Functional Architecture The ATM SATCOM system implements a mobile communication sub-network, designed for transparent integration into a more global Aeronautical Telecommunication Network infrastructure. The system operates over geostationary satellites. Each satellite provides a service over a wide region. The complete system can be composed of complementary interoperable regional systems in order to achieve worldwide coverage. The three basic elements of the ATM SATCOM architecture are: 1. The Geostationary Satellite, 3 ITU AMS(R)S allocation in L-band Page 134 Final Edition Number: 1.0

147 2. The Airborne Terminal (AES), and 3. The Ground Earth Station (GES). The ATM SATCOM network can be organised either in multi-star configuration, with several GES handling a set of AES (Figure H-1) or with a unique central GES. Fixed to mobile connectivity is provided (i.e. ground station to/from aircraft), but not mobile to mobile (i.e. No direct aircraft to aircraft communications). The multi-star configuration capability allows implementations with multiple operators of ATM SATCOM. H.1.3 Services Provided & Key Features Figure H-1 Multi-star network concept The ATM SATCOM system is designed to provide highly reliable packet data service. The objective is to provide guaranteed performances to end users, as required for safety related services. Several QoS classes are supported. The network protocols provide the necessary mechanisms for end-to-end quality of service negotiation and control. The main parameters taken into account in the specification of the classes of services are the transit delay and the residual error rate. In terms of connectivity, the network provides bidirectional and unidirectional data services (for periodic reporting for instance), as well as broadcast services from ground to air. In addition to the data service, the ATM SATCOM service provides a low codec duplex packet voice communication service (4.8kbps or 2.4kbps vocoding). H.1.4 Air Interface Description Two options are being considered: a baseline air interface based on CDMA, which would easily allow multiple access from several GESs, and an air interface based on DVB-S2 for the forward link, which would be optimum within a centralised architecture using a single GES. Baseline Air Interface The baseline air interface is based on Code Division Multiple Access (CDMA), both in forward and return link. All the carriers share the same basic characteristics (same Edition Number: 1.0 Final Page 135

148 waveform and data rate) and are associated to CDMA codes. Several CDMA carriers can be simultaneously transmitted in forward and return links to provide multi-user access. Further, to optimise access efficiency, a Time Division Multiple Access (TDMA) over CDMA scheme is selected in return link. Above the physical CDMA carriers, logical channels are defined. The proposed set of logical channels essentially re-uses the classical AMSS structure, and extends it with additional channels specifically designed to carry critical information. Table H-1 Channels Definition Table H-1 above, provides the definition of the ATM SATCOM channels, while Figure H-2 below represents the channel distribution scheme of the ATM SATCOM in a basic system instantiation over a geostationary satellite. Figure H-2 Channel Distribution For each GES the following channels are used, (whose functionalities are aligned with those of AMSS channels): Page 136 Final Edition Number: 1.0

149 - several forward data traffic channels (Pd, D), with one (Psmc) used for network entry, o 1 return logon channel (Rsmc), o several concurrent return access channels (Rd), o several non-concurrent return access (or critical traffic) channels (D), o several return traffic channels (T), o several duplex voice channels (C). Table H-2 below provides a summary of the main characteristics of the ATM SATCOM waveform for the physical and link layers. Table H-15-2 Waveform Summary The following types of framing have been defined in [RD.4]: Continuous carrier framing, applicable to Pilot/reference carriers. Framing of asynchronous Random Access type carriers Framing of Synchronous Raw CDMA type carriers TDMA over CDMA structure framing, including Super-frame and time-slots. A coding rate of ½ is used (turbo-coding), that together with the QPSK modulation results in a symbol duration equal to the bit duration. In consequence, the frames presented below represents the symbol and the bit contents. The spreading is implemented with gold-codes. The most significant framing types are introduced hereafter, corresponding to TDMA/CDMA packet data carrier structure, and Voice/Data multiplex carrier structure. The TDMA/CDMA framing presented in the Figure below, is used to transmit packet data information in forward and return links. Edition Number: 1.0 Final Page 137

150 Figure H-3 TDMA/CDMA General Carrier Frame Structure With The raw CDMA framing, presented in Figure H-4, is used to transmit packet data or voice information in forward and return links. The framing supports data and voice multiplexing. With- Figure H-4 General Burst Structure for Voice/Data multiplexing Page 138 Final Edition Number: 1.0

151 Forward Link Air Interface Option Optionally, the forward link air interface can be replaced, or complemented, by a single Time Division Multiplex carrier. In this option, the forward link carrier will be implemented according to the DVB-S2 standard, where the throughput can be variable. Figure H-5 Channel Distribution In the forward link, one single TDM (Time Division Multiplex) conveys all the data (both signalization and traffic), using the GSE protocol (Generic Stream Encapsulation) to carry the data. This protocol allows for direct encapsulation of IP and other network layer packets over DVB-S2 physical layer frames. GSE supports several addressing modes (multicast & Unicast addresses, no address, MAC address, etc). The Figure H-6 below shows the GSE encapsulation over a DVB-S2 BBFrame: Figure H-6 GSE Frame encapsulation The Payload Data Unit carries the data useful for upper layers. GSE offers an excellent performance in terms of overhead (2-3%) using a protocol of low complexity. The Table below, provides a summary of the main characteristics of the ATM SATCOM waveform for the forward physical and link layers in the DVB-S2 option. Edition Number: 1.0 Final Page 139

152 Table H-3 Waveform Summary Such a solution will allow taking advantage of DVB-S2 performances in terms of spectrum efficiency due to the use of powerful coding techniques. The satellite power required will therefore be lower which means a cheaper solution. Moreover, the use of a standardized and proven air interface would reduce the cost of ground equipment because the technology is already available and new developments are not required. On the other hand, it should be noted that a TDM solution like DVB-S2 is based on a centralized architecture, where the traffic is handled by a single Ground Earth Station: this has some advantages (lower overall cost of the system, broadcasting capability, easier operation, etc.) and some drawbacks (potential issues linked to the ownership of the central GES in a multinational environment, single failure point). H.1.5 Standards The objective of the ATM SATCOM initiative is to develop an open interoperable satellite mobile communication system standard. At lower level, the solution will rely on new standards for the avionics, as well as existing standards, such as ARINC standards for avionics (e.g. ARINC 471 or 481 for AES architecture) and ATN SARPS for networking. Industry standard products for unitary communication modules (DVSI 4.8k vocoder, industry standard turbo-fec chips, etc..) will be used to assemble the solution. H.1.6 Technology Readiness Level (TRL) A system prototype validating proper operation of the CDMA access scheme has been developed by ESA, and qualified with Artemis satellite in At network level, multiple access performance, and access from several ground stations has been demonstrated. Voice services demonstrations have been executed showing the good audio quality provided by the satellite system. Different data services demonstrations have been performed with a representative set of ATS and AOC applications. The GES modem prototypes developed would be functionally close to the final operational product (Figure H-7). As far as the avionics is concerned, the development of a new modem unit (Satellite Data Unit SDU) according to aeronautical standards is required. Other avionics components (AERO-L antennas, HPAs) are already available from the classic AMSS system; they would however benefit from further developments to lower their unit cost. Page 140 Final Edition Number: 1.0

153 Figure H-7: System Prototype Elements Regarding the DVB-S2 option, this access scheme would benefit from existing commercial products (GES components, chipsets, etc.). DVB-S2 performances for satellite systems have been demonstrated in-depth during laboratory and field trails and this access scheme is implemented for commercial broadcasting services over satellite. H.1.7 APPLICATION OF TECHNOLOGY TO ATM Introduction The ATM SATCOM system is specifically designed to serve aeronautical users. The present section will present how the constraints and requirements derived from ATM users according g to the COCR document [RD.2] have been taken into account in ATM SATCOM solution definition, and which are the missions that the ATM SATCOM system intends to fulfil. Concept of Use The ATM SATCOM solution will be used primarily to support data link services. In core Europe, where VHF spectrum is getting congested, the ATM SATCOM system will complement the ground systems by providing extra communication capacity, or an enhancement of data link performance. Outside congested areas, ATM SATCOM will provide seamless connectivity with improved performance compared to classic AMSS either for voice or data services. Edition Number: 1.0 Final Page 141

154 Spectrum Considerations The ATM SATCOM system is intended to operate in ITU AMS(R)S allocation (1.5/1.6 GHz). As this band is already protected for the provision of aeronautical services in relation to safety and regulatory of flight, no new frequency band allocation should be required. ITU Radiocommunications Regulation states the following concerning the AMS(R)S band: 5.357A In applying the procedures of Section II of Article 9 to the mobile-satellite service in the bands MHz and MHz, priority shall be given to accommodating the spectrum requirements of the aeronautical mobile-satellite (R) service providing transmission of messages with priority 1 to 6 in Article 44. Aeronautical mobilesatellite (R) service communications with priority 1 to 6 in Article 44 shall have priority access and immediate availability, by pre-emption if necessary, over all other mobilesatellite communications operating within a network. Mobile-satellite systems shall not cause unacceptable interference to, or claim protection from, aeronautical mobile-satellite (R) service communications with priority 1 to 6 in Article 44. Account shall be taken of the priority of safety-related communications in the other mobile-satellite services. (The provisions of Resolution 222 (WRC- 2000) shall apply.) (WRC-2000) Preliminary spectrum evaluations for a scenario providing coverage of ECAC indicate that around 3 MHz [RD.1] would be required to support future ATM services at horizon Further, as the legacy AMSS system already operates in this band, no further work is expected in terms of EMC and certification at aircraft level. H.1.8 Airspace Application The ATM SATCOM system is intended to provide the following services in the different airspace : o Continental : ATS datalink and AOC datalink in en-route and TMA phases of flight o Remote and Oceanic : ATS datalink & voice, AOC datalink & voice. In dense airspace, some future datalink applications will require highly reliable datalink performance [RD.2]. Preliminary studies show that two parallel radio-systems will be required to meet the required performance. Parallel operation of a terrestrial radiocommunication component along with the ATM SATCOM system may therefore be foreseen for some services. H.1.9 ATM services supported The ATM SATCOM system is principally intended to support data link deployment. The ATM services supported have been identified according to COCR [RD.2]. The supported services include a sub-set of ATS services specified in COCR [RD.2] and all AOC services. The different datalink services have been sorted in four different groups as indicated in Table H-4. Voice services will be provided for oceanic and remote airspace operations. In continental airspace, the dimensioning of the voice service by satellite has so far been based upon a backup Page 142 Final Edition Number: 1.0

155 capability only. Table H-4 ATM Services Concerning network level issues, the ATM SATCOM system is designed to comply with ATN specifications, although derivations of ATN/OSI and ATN/IPS stacks could be considered. This subject is currently being actively addressed in ICAO ACP-WGN; ultimately the ATM SATCOM system will be aligned to the selected option at regional level, including possibility to support dual stack implementations. Both options would include mobility management and network security features. H.1.10 Proposed Architecture for Technology System With geostationary satellites, world-wide coverage capability can be provided, as an aggregation of several regional systems. A regional implementation of the ATM SATCOM system is composed of the following elements: Space segment two payloads hosted on distinct Geostationary Satellites, transparent transponder from feeder to mobile link and vice versa, one or several antenna spots, offering a complete coverage of the region considered, one or several frequency channels in AMS(R)S band, Ground segment two non-collocated Network Management Stations (nominal and backup), which can be used for each satellite (i.e. no more than two distinct geographical sites are required), a set of GES, Support segment System Management Network (terrestrial network), Monitoring and Control Facility, User segment a set of mobile AES terminals in the region considered. The AES may be further segregated in several sets according to their class of performance. Edition Number: 1.0 Final Page 143

156 Figure H-8 System Architecture H.1.11 Performance Assurance Initial performance assessment has been carried out to demonstrate that the ATM SATCOM system can comply with the aviation community requirements as expressed in COCR [RD.2], for each set of services taken into account [RD.1], both in terms of Quality of Service (availability, integrity, transit delay), and in terms of System Capacity. Quality of Service compliance has been analysed through theoretical demonstrations (availability & integrity), complemented by simulations at Medium Access Protocol level. A channel loading analysis as been developed in [RD.4] through queuing simulations. It was shown that the system could deliver forward traffic in less than 1.2s with a channel load of 80% in the forward link, and within 4s with a channel load of 75% in the return link see Table H-5 below. These values are generally compliant to [RD.2] requirements, except for some COCR phase 2 services such as A-EXEC for instance which is currently excluded from the ATM SATCOM specification [RD.1]. Page 144 Final Edition Number: 1.0

157 Table H-5 MAC Simulation Results A system capacity evaluation for the ECAC case, using the latest services assumptions from COCR, and a traffic growth forecast from STATFOR has been performed. The order of magnitude lies around 500kbps for Unicast services, and 150kbps for broadcast services at horizon According to the models developed in [RD.4], the system would require about channels to handle the traffic, and circa 3MHz of bandwidth. Taking into account a DVB-S2 solution for the forward link, current estimates foresee a required bandwidth of less than 2 MHz; depending on the modulation and coding average for each communication, spectrum occupancy could potentially be even less than 1.5 MHz. From the system capacity analysis, the AOC service WXGRAPH (meteo data) has been identified as one of the most dimensioning service in the future. This service can be efficiently provided through periodic broadcast, thus saving an important part of the required bandwidth. Thanks to the global coverage provided by the ATM SATCOM solution over the region considered, the required bandwidth to support this service can be reduced down to about 45kbps, an order of magnitude less than with any terrestrial cellular system implementation. H.1.12 STATUS OF TECHNOLOGY The ATM SATCOM system is built on robust and mature technology. No specific technological difficulties are expected in its implementation. A functional system prototype has been developed with minimal custom developments. The development of an industrial aeronautical version of the product requires the production of the necessary standardisation material (MASPS, MOPS), and the validation of the system performance through pilot system experimentation. Definition of new industrialisation processes in order to target a wider market could allow for reduction of unit production cost of equipment and make it affordable for a vast majority of aircraft categories. Edition Number: 1.0 Final Page 145

158 H.1.13 References Page 146 Final Edition Number: 1.0