GALILEI. Complementary Systems: VDL Mode 4

Transcription

1 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 1 Sustainable Mobility and Intermodality Promoting Competitive and Sustainable Growth GALILEI Complementary Systems: VDL Mode 4 Written by Responsibility - Company Date Signature Jens Redeborn, Abdul Tahir Swedavia Verified by Niclas Gustavsson Swedavia Certified by Umberto Guida Alenia Spazio WBS Code Classification : C.2.B.8 : Final Issue

2 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 2 THE INFORMATION IN THIS DOCUMENT IS PROVIDED AS IS AND NO GUARANTEE OR WARRANTY IS GIVEN THAT THE INFORMATION IS FIT FOR ANY PURPOSE. THE USER THEREOF USES THE INFORMATION AT ITS SOLE RISK AND LIABILITY. FURTHERMORE, DATA, CONCLUSIONS OR RECOMMENDATIONS IN THIS REPORT ARE PROVIDED ON THE BASIS THAT SUCH INFORMATION IS SUBSEQUENTLY, AND PRIOR TO USE, VERIFIED BY THE PARTY WISHING TO USE THAT INFORMATION.

3 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 3 CHANGE RECORDS ISSUE DATE : CHANGE RECORD AUTHOR First draft issue. Draft issue (Internal updates) Draft issue (Internal updates) J. Redeborn Final Issue J. Redeborn 1.A Update per comments from Industrial Team A. Tahir 1.B Update per comments from Industrial Team as well as comments from Alenia Spazio during telecon A. Tahir, J. Redeborn 1.C Update based on from Alenia Spazio A.Tahir, J.Redeborn Issue 1.1 A.Tahir, J.Redeborn

4 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 4 TABLE OF CONTENTS 1 PRESENTATION OF THE STUDY SPECIFIC REFERENCES Acronyms Reference Documents VDL MODE SYSTEM DESCRIPTION LOCAL FUNCTIONS AND SERVICES Communication Service Functions and applications Surveillance applications Communication applications Navigation applications Secondary Navigation in VDL Mode 4 based on triangulation Operational benefits of secondary navigation VDL MODE 4 LOCAL PERFORMANCES VDL MODE 4 COVERAGE VDL MODE 4 TRANSCEIVER ASPECTS VDL Mode 4 Transceiver Hybrid TRANSCEIVER Spectrum for Hybrid Transceiver COMBINATION IN CRITICAL ENVIRONMENT CRITICAL ENVIRONMENT VDL MODE 4 AND GNSS IN CRITICAL ENVIRONMENT EXTENSION TO GALILEO Brief Description of VDL4- Augmentation with GNSS VDL4-Augmentation with Galileo for Aviation VDL4-Augmentation with Galileo for Multimodal Applications Universal Automatic Identification System for Maritime RECOMMENDATIONS INTEROPERABILITY CERTIFICATION AND STANDARDISATION Certification Objective Certification Process...40

5 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: Development and Certification Standards LEGAL ASPECTS SECURITY ISSUES CONCLUSION... 47

6 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 6 LIST OF FIGURES Figure 2-1 Time-slots in VDL Mode Figure 2-2 Ground station transmissions Figure 2-3 Layered Structure of VDL Mode Figure 2-4 Services Supported by VDL Mode Figure 2-5 Overview of GNSS Navigation Concept Figure 2-6 Secondary Navigation in VDL Mode Figure 2-7 VDL Mode 4 Coverage from Flight Test at Stockholm/Arlanda Airport Figure 2-8 Illustration of Cell Shrinkage using Robin Hood principle Figure 2-9 Block Diagram of a Typical VDL Mode 4 Transceiver for CNS applications Figure 2-10 Detailed Hybrid GNSS Transceiver Figure 2-11 VDL Mode 4 and Galileo Spectrum Allocation Figure 3-1 Basic VDL4-Augmentation with Galileo Concept Figure 3-2 VDL Mode 4 Airborne and Ground Subsystem for CNS/ATM Figure 3-3 Overview of the AIS Figure 4-1 Typical Development/Certification Process used in Civil Aviation Figure 4-2 Top Level Safety Allocation Process Figure 4-3 Typical Safety Assessment Process Model Figure 4-4 Software Life Cycle Process LIST OF TABLES Table 2-1 VDL Mode 4 Target Performance for CNS Services Table 3-1 VDL4-Augmentation Performance Improvement progression Table 4-1 Certification Authorities for Various Segments... 42

7 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 7 1 PRESENTATION OF THE STUDY The objective of this study is to provide the basic principle of VDL Mode 4 as part of Galileo and its use in Communication, Navigation and Surveillance (CNS) in Aviation. The use of VDL Mode 4 is not limited to aviation; it provides similar functionality for multi-modal applications as it does for aviation. These include maritime uses such as Automated Identification System (AIS). The principle focus of this presentation is VDL Mode 4 and how it compliments Galileo for achieving enhanced performance for CNS usage. The target objective is to achieve these capabilities during all phases of flight i.e. for entire gate-to-gate operations. VDL Mode 4 is a datalink developed to provide a high throughput and optimal data broadcast with minimal losses.. VDL Mode 4 is a robust Self-organising TDMA datalink, which can be used for CNS functions. Conversely, navigation data derived from Galileo would be used in aviation for surveillance for ADS-B and other aviation applications. The precise timing available from Galileo provides precise UTC signal for the synchronisation of.vdl Mode 4 broadcasts. The precise timing also forms a basis for a secondary navigation function which can be derived from the VDL Mode 4 as a backup navigation source when a GNSS based primary navigation function is not available due to lack of satellite visibility or other causes. Hence VDL Mode 4 and Galileo form a proper compliment to Galileo whereby navigation and precise timing are available for complimentary use and a convenient way to field Galileo receivers early.

8 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: SPECIFIC REFERENCES ACRONYMS ADS ADS-B AIS APV ASAS A-SMGCS ATC ATM ATS CAA CDTI CFIT CNS CPDLC DAS DCL DGNSS DGPS DLS DoS EC EGNOS ESA FAA FAS FIS-B GALA GALILEO GBAS GEMINUS GEO Automatic Dependent Surveillance Automatic Dependent Surveillance Broadcast Automatic Identification System APproach with Vertical guidance Airborne Separation Assurance Systems Advanced Surface Movement Guidance and Control System Air Traffic Control Air Traffic Management Air Traffic Services Civil Aviation Authority Cockpit Display of Traffic Information Controlled Flight Into Terrain Communication, Navigation and Surveillance Controller-pilot data link communications Delegated Airborne Separation Departure CLearance Differential GNSS Differential GPS Data Link Services Directory of Services European Commission European Geostationary Navigation Overlay Service European Space Agency Federal Aviation Administration Final Approach Segment Flight Information Service Broadcast GALILEO overall Architecture study Global navigation satellite system Ground Based Augmentation System GALILEO European Multimodal Integrated Navigation User Service GEOstationary satellite

9 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 9 GIS GLONASS GNSS GNSSP GPRS GPS GR GRAS GSC ICAO ISO LME MAC MEDUP MFF MOPS NEAN NEAP NLTB NPA NPV NUP PVT QoS RF RNAV RNP SAR SARPS SBAS SMGCS STDMA TIS-B TRAN TTA UMTS Geographic Information System GLObal NAvigation Satellite System (Russia) Global Navigation Satellite System GNSS Panel General Packet Radio Service Global Positioning System (USA) General Request message Ground based Regional Augmentation System Global Signalling Channel International Civil Aviation Organisation International Organisation for Standardisation Link Management Entity Media Access Control Mediterranean Update Program Mediterranean Free Flight Minimum Operational Performance Standards North European ADS Network North European CNS/ATM Application Project Northern Latitude Test Bed Non Precision Approach Non Precision approach with Vertical guidance NEAN Update Program Position Velocity Time Quality of Service Radio Frequency area NAVigation RadioNavigation Plan Search And Rescue Standards And Recommended Practices Satellite Based Augmentation System Surface Movement Guidance and Control Server Self-organising Time Division Multiple Access Traffic Information Service Broadcast Terrestrial Regional Augmentation Network Time To Alarm Universal Mobile Telecommunication System

10 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 10 UTC VDL VOR VSS WAAS Universal Co-ordinated Time VHF Data Link Very high frequency Omni-directional Radio range VDL Mode 4 Specific Services Wide Area Augmentation System REFERENCE DOCUMENTS RD 1 RD 2 DD020 : Required Performances for Local Application DD021 Complimentary Systems: Functions and Performance RD 3 MRD Mission Requirements Document Issue 1 RD 4 SRD System Requirements Document Issue 1 RD 5 RD 6 RD 7 MASPS for A-SMGCS, EUROCAE; Eurocae ED 108 VDL Mode 4 MOPS; Eurocae DRAFT ICAO SARPS for GNSS Amendment Letter 77; November 2001; ICAO RD 8 ED-12B Software Considerations in Airborne Systems and Equipment Certification, Eurocae RD 9 "Secondary navigation in VDL Mode 4", Larry Johnsson, Aeronautical Mobile Communications Panel, Madrid, April RD 10 Study on the options of time synchronisation in the VDL Mode 4 Datalink System; Issue 1.2; Eurocontrol RD 11 DO 242 Minimum Aviation System Performance Standards For Automatic Dependent Surveillance Broadcast (ADS-B), RTCA RD 12 VDL Mode 4 Master Document; Issue 2, Swedish CAA, September 2001 RD 13 RD 14 ED 78A Guidelines for Approval of the Provision and Use of Air Traffic Services supported by Data, Eurocae ED 72A MOPS for Airborne GPS receiving equipment for supplemental means of navigation, Eurocae

11 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 11 2 VDL MODE SYSTEM DESCRIPTION VDL Mode 4 is an ICAO standardised 1 STDMA VHF data link, providing digital communications between mobile stations (aircraft and airport surface vehicles) and between mobile stations and fixed ground stations. It was developed for CNS/ATM aviation applications, supporting various services including broadcast applications (e.g. ADS-B, TIS- B, FIS-B and GNSS) as well as point-to-point communications (e.g. ADS-C). VDL Mode 4 protocols support ADS-B and similar applications through the broadcast of short repetitive messages, with graceful adaptation to increasing traffic loads. The core of VDL Mode 4 is the ADS-B Service, other services such as TIS-B, FIS-B, GNSS etc., are add on services that are being considered to enhance the use of VDL Mode 4 for aviation. Navigation applications of VDL Mode 4 is currently not being considered for standardisation by ICAO VDL Mode 4 transmits digital data in a standard 25 khz VHF communications channel and divides the communication channel into a large number of time slots. The start of each slot is an opportunity for a station to transmit as shown in Figure slots per minute Figure 2-1 Time-slots in VDL Mode 4 VDL Mode 4 is built on the Self-organising Time Division Multiple Access (STDMA) technology, in which the time-slots are synchronised, to UTC. A possible source for precise UTC is GNSS including Galileo. The stations advertise their intention to transmit in a specified time-slot by means of a reservation protocol carried in a prior transmission see figure 2-2. For convenience, a group of contiguous time slots spanning a period of 60 seconds is termed a superframe. The superframe contains 4500 slots (equivalent to 75 slots per 1 VDL Mode 4 is currently standardised within ICAO for Surveillance applications only.

12 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 12 second). Each time slot may be used by a radio transceiver (mounted on aircraft, ground vehicles or at fixed ground stations) for transmission of data. The exact timing of the slots and planned use of them for transmissions are known to all users in range of each other, so that efficient use of the data link can be made and users do not transmit simultaneously. As a result of this self-organising protocol, VDL Mode 4 is capable of operating outside the coverage of a ground infrastructure and can therefore support air-air as well as ground-air data communications and applications. In high density airspace, a ground infrastructure may be used to manage the system and improve overall performance. VDL Mode 4 operates in the aeronautical VHF spectrum band, i.e MHz. The discrimination property of VHF, which allows a station to select the stronger of two overlapping signals, enables efficient re-use of time slots and spectrum. A pair of Global Signalling Channels (GSC) will be allocated for worldwide use. These channels will be sufficient to support ATM in most areas, but may need to be complemented by Local Signalling Channels (LSC) needed in busy terminal areas and at high-density airports to supplement the GSCs for ADS-B, and possible additional VHF-channels required for uplink and downlink of application data. Principles for assigning VDL Mode 4 channels are yet to be developed. Appropriate frequency management techniques must be used when determining the set of physical VHF frequencies in a certain area, considering the co-channel and adjacent channel interference (CCI/ACI) characteristics of the VDL Mode 4 transceivers. Ground stations will generally transmit bursts containing several different types of messages. There are several EC sponsored programs one of them called NUP (NEAN Update Program) was set up to broadcast different types of messages for various different services an example of that is shown in Figure 2-2. The figure shows uplink transmissions containing: ADS-B messages (synchronisation bursts); Directory of Services messages (DoS); TIS-B messages; FIS-B messages; GNSS augmentation data General Request messages (GR).

13 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 13 System control DoS TIS-B FIS-B GNSS GR Augmentation Blocked area Ground station transmissions Figure 2-2 Ground station transmissions The figure also shows: Directed reporting of some aircraft. These are aircraft that are reporting under direction of the ground station and they have been directed into the slots immediately after the uplink transmission. Ground quarantine slots. These are the slots immediately following a ground station transmission or a transmission from a mobile in directed reporting. They are not used for ADS-B messages by autonomous mobiles. Blocked slots. These are typically reserved slots for ground station transmissions only, in order to protect the transmitted information from unintentional interference from other transmitters, but mobile stations may also be directed into blocks. In an area with several active ground stations their pre-planned transmissions are co-ordinated and the blocked area is covering all transmissions from these ground stations. As shown in Figure 2-3 VDL Mode 4 sub-system implements the three lower layers of the OSI model: Layer 1 (Physical layer) provides transceiver frequency control, bit exchanges over the radio media, and notification functions. These functions are often known as radio and modulation functions. The ICAO VDL SARPs define the physical layer for VDL Mode 4: The modulation scheme is Gaussian Filtered Frequency Shift Keying (GFSK), at a nominal bit rate of 19,200 bits/s. Layer 2 (Link Layer): is split into three sublayers and a management entity: The Media Access Control (MAC) sublayer provides access to the Physical layer by a simple Time Division Multiple Access (TDMA) algorithm under the control of the next higher sublayer. It also provides system time functions to co-ordinate the TDMA channel access. The VDL Mode 4 specific services (VSS) sublayer provides control of channel access using a self-organising mechanism. The VSS also support a number of ground controlled

14 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 14 access protocols. The basic services are built on reserved, random and fixed access to the TDMA slots and support broadcast and point-to-point communication. The Data Link Services (DLS) sublayer is composed of the Aviation VHF Link Control (AVLC) derived from the High Level Data Link Control (HDLC) protocol (ISO 3309) whose main functions are frame exchanges, frame processing and error detection. The DLS protocols are adapted to make best use of the unique VSS channel access protocols. The Link Management Entity (LME) is in charge of the links between peer DLS sublayers and also the maintenance of the broadcast link functions.

15 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 15 ATN VDL Mode Subnetwork Position source Link control data and parameters Frames and DLS user parameters LME Synchronization bursts, Peer entity contact table, Net entry Link establishment and maintenance (exchange identity protocols), Directory of services XID frame data, DLS user parameters Sync burst data, VSS user parameters DLS sublayer Re-transmission, Frame error detection, DLS burst formatting, Mode 4 data transfer protocol, (ground-air) and (air-air), Mode 2 data transfer protocol VDL Mode 4 specific applications Burst and frame data, VSS user parameters Received burst and frame data, VSS user status information VSS Burst formatting, Self organizing TDMA Slot selection, Reservation table, Burst encoding, Reserved access Reservation table update, Burst decoding, Data error detection Bursts and frames, Time to send, Access control (reserved or random) Received burst and frame data, Unsent random transmissions MAC Slotted TDMA, Time synchronization Transmission formatting, Burst error detection Slot occupied/not occupied processing, Arrival time measurement Physical Transmission, nominal start of transmission Frequency control, Data encoding Transmission timing, Transmitter shutdown Received transmission, Channel busy/idle notification Data decoding, Signal quality notification, Channel sensing, Arrival time measurement VHF Figure 2-3 Layered Structure of VDL Mode 4

16 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 16 Layer 3: The VDL SARPs defines only the lowest network sublayer of layer 3 (SNAcP). It is compliant with the subnetwork sublayer requirements defined in the ATN SARPs and conforms to the ISO 8208 (or network layer of CCITT X.25). It provides packet exchanges over a virtual circuit, error recovery, connection flow control, packet fragmentation, and subnetwork connection management functions. VDL Mode 4 operation is built up from the following fundamental features, which support various CNS operations: a. A robust modulation scheme for encoding data in each slot. VDL Mode 4 supports Gaussian Filtered Frequency Shift Keying (GFSK) with a modulation rate of 19,200 bits/sec. b. A self organising time division multiplex access (STDMA) frame structure. In VDL Mode 4, channel time is divided into fixed length time slots. A superframe consists of a group of slots that span a period of 60 seconds and contains 4500 slots (equivalent to 75 slots per second). c. A timing reference providing a unique marker for the start of each communications slot. The timing concept used in VDL Mode 4 is based upon Universal Co-ordinated Time (UTC). The primary source during normal operation is typically GNSS which includes Galileo, but other sources may be used as long as they can be related to UTC and satisfy the performance requirements. Hence VDL Mode 4 derives the benefit of high precision timing source from GNSS including Galileo In the event that a station loses its primary source of UTC time, it may resort to a failure mode known as secondary timing of reduced precision, which is a backup mode. A possible source of secondary time may be derived from the time of arrival of synchronisation bursts received from another station declaring primary time. A further failure mode (known as tertiary timing) allows a station to transmit when it is unable to derive time from primary or secondary time sources. In tertiary time, a station maintains synchronisation to an estimate of the mean slot start time of a set of stations. It should be noted that secondary timing is only used as backup modes in case of a possible failure of all the GNSS satellite systems. d. Position information from the aircraft s navigation system, which could be GNSS, including Galileo derived is used to organise access to the slots. If a station loses its source of position information it may continue to derive position from synchronisation bursts received from other stations (known as secondary navigation) shown in Figure 2-6. Stations operating on secondary or tertiary timing do not offer certified data quality and thus cannot be used for derivation of secondary navigation. e. A flexible message structure that can support a wide range of broadcast and data transfer protocols such as ADS-B and point-to-point communication. f. A slot selection function that determines when a station can access the channel and maintains information on the current and planned slot assignments. g. A slot access management function, controlling the use of each slot. h. A number of link management functions that support access to data link services on a wide range of channels.

17 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: LOCAL FUNCTIONS AND SERVICES VDL Mode 4 local functions and services described in this section are based on a number of EC sponsored programs. These projects are today exploring the benefits of such applications with VDL Mode 4 as a key component to enable the different applications through services. The most recognised project within this field is the NUP II (North European ADS-B Network Update Programme) Phase II which is a direct follow up on NUP phase I and the NEAN projects. The main objective in NUP II is to Establish a European ADS-B network based on global standards supporting certified applications and equipment in synergy with the European ATM concepts providing benefits to ATM stakeholders. The development of different ADS-B applications is the core process in NUP phase II, such as ADS-B in Non Radar Environment, off-shore operations, surface movement operations (SMGCS), air-to-air operations and ADS-B in ATC. Although the main focus is on ADS-B the scope is not limited to this. The use of complementary services like TIS-B (Traffic Information Service- Broadcast), FIS-B (Flight Information Services-Broadcast) and services in the point-to-point area will also be investigated during the projects life cycle. Other Projects are the MFF (Mediterranean Free Flight Programme) and MEDUP (Mediterranean Update Programme). The main goal of ADS-MEDUP is the construction of a pre-operational infrastructure serving a large portion of the Mediterranean airspace, which includes key Ground and Airborne CNS/ATM elements based on satellite navigation and VDL Mode 4 data link as enabling technologies. The MFF programme is investigating Free Routing and Free Flight providing technical and operational evaluation of integration interoperability and safe use of CNS/ATM technologies and applications (e.g. operational requirements and procedures based on the use of new CNS/ATM technologies enabling the introduction of free flight operations in the Mediterranean area). Also to verify appropriate new operative procedures for ATM staff and crew in free routing and free flight scenarios such as delegation of separation responsibility from ATC to aircraft and vice versa, through simulations and flight trials using specially equipped aircraft and controller working positions. A close coordination among these and other programmes in the same field are conducted in order to obtain interoperability. VDL Mode 4 provides a platform of services on which to develop new applications. Such applications operate in a wide range of operational scenarios from worldwide civil aviation to the local airport environment. Most of these applications that are imbedded in the services provided by VDL Mode 4 are complemented by GNSS, which includes Galileo. Example applications include: 1. Automatic Dependent Surveillance-broadcast (ADS-B); 2. Differential GNSS; utilised for augmentation as shown in Figure Surface Movement Guidance and Control (SMGCS); 4. Uplink information such as traffic, meteorological, etc.

18 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 18 User functions & applications Controller-Pilot Data Link Communication (CPDLC) ADS contract (ADS-C) Non- ATN ground-air communication Air-air communications Air-air trajectory negotiation Precision navigation Non Precision Approach Flight Information Service- broadcast (FIS-B) Traffic Information Service - broadcast (TIS-B) Cockpit Display of Traffic Information ( CDTI) Airborne separation assurance (ASAS) Precision Runway Monitoring (PRM) Surface movement surveillance Secondary navigation Core functions supported VDL Mode 4 ATN GNSS Augmentation ground-air data broadcast ADS-B VDL Mode 4 Services ground-air End-to-end communications ATN services ground-air air-air ground-air air-air End-to-end communications Data broadcast VDL Mode 4 specific services ground-air air-air Position broadcast Figure 2-4 Services Supported by VDL Mode 4 VDL Mode 4 provides a platform on which to develop new, yet not fully defined applications. Such applications operate in a wide range of operational scenarios from world-wide civil aviation to the local airport environment. Figure 2-4 illustrates VDL Mode 4 user functions and applications and their relationship to the core functions and communication services supported by the system. The description in this section expands on the diagram COMMUNICATION SERVICE VDL Mode 4 supports two different types of communication services: VDL Mode 4 specific services (VSS); VDL Mode 4 ATN data link services (DLS). The VDL Mode 4 specific services include broadcast and point-to-point (addressed) communications with a minimum of overhead information for exchange of time-critical data. VDL Mode 4 constitutes an ATN sub-network and thus provides fully ATN compliant communication services. Together these services support several broadcast and end-to-end communication functions that supporting a range of air-ground and air-air ATM applications. VDL Mode 4 services are accommodated on multiple VHF channels. While DLS channels must be separated from those supporting VSS, various broadcast functions and applications could share a channel. The possibilities for channel sharing depends on various constraints such as channel availability, certification requirements and ATS regulations and may differ between states and regions FUNCTIONS AND APPLICATIONS This section expands on the VDL Mode 4 ATM functions and applications identified in Figure 2-4 following the traditional subdivision into Communications, Navigation and

19 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 19 Surveillance (CNS). As ADS-B is the fundamental service provided by VDL Mode 4, Broadcast of data is the fundamental VDL Mode 4 technique, while point-to-point communications could be seen as a complement necessary for realising specific needs in the future ATM concept. As an enabler of important applications and services such as ATS surveillance, cockpit display of traffic, surface movement surveillance and airborne separation assurance, ADS-B is the key VDL Mode 4 service. Surveillance applications are described first, followed by communications and navigation applications. It should be noted that the boundaries between C, N and S are somewhat blurred, as all functions and applications essentially are based on (data link) communications. In this section, the intended use of an individual application has been used to determine the group in which it is described. Use of multiple channels The number of channels required to support VDL Mode 4 C, N and S services in a certain area will depend on local and regional conditions such as the traffic density (affecting the channel load), certification requirements, ATS regulations and spectrum availability. Whereas a single channel may be acceptable to support ADS-B, GNSS augmentation, TIS-B and FIS-B in one area, multiple channels may be required to support ADS-B and TIS-B alone in a highdensity terminal area, supplemented by separate channels that support any augmented GNSS navigation and FIS-B Surveillance applications ADS-B The ADS-B function is an evolving technology that uses the VDL Mode 4 synchronisation burst message formats to broadcast regularly an aircraft or vehicle s identity, position, altitude, time, intent and vector information for use by other users, both mobiles and ground stations. Because position reporting is an integral part of communications management in VDL Mode 4, the core elements of ADS-B are already present on the link. ADS-B supports many mobile-mobile surveillance applications such as cockpit display of traffic information (CDTI), airborne situational awareness (AIRSAW) and station keeping. When the VDL Mode 4 system also includes ground stations it is also able to support applications such as Advanced Surface Movement Guidance and Control Systems (A- SMGCS), enhanced ATC, Search And Rescue (SAR) coordination, etc. Cockpit Display of Traffic Information (CDTI) One of the greatest benefits of VDL Mode 4, and a natural extension of its ADS-B capability, is that it provides a pilot with situation awareness using CDTI. This means that a display in the cockpit can show the pilot the positions of all other aircraft in the vicinity with a range of up to 200 nautical miles. Traffic Information Service (TIS) TIS is an ATM function that uses a data link to upload radar surveillance data from the ground to aircraft to supplement ADS-B reports in airborne surveillance. VDL Mode 4 supported broadcast TIS (TIS-B) will provide ADS-B equipped aircraft with position information from non-equipped aircraft to provide situational awareness of all nearby traffic. Thus TIS-B is an important function to deliver benefits from ADS-B in a partially equipped environment and during the transition from a radar-based to ADS-B surveillance environment. TIS-B reports are typically restricted to position information on aircraft not equipped with ADS-B.

20 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 20 Air-to-air surveillance Basic air-to-air surveillance is provided by ADS-B. The direct air-to-air communication (addressed) capability of VDL Mode 4 can be used to implement a temporary pair wise crosslink for trajectory negotiations between two aircraft in the Free Flight concept. Such a crosslink is used to ensure that action taken by one aircraft in a conflict situation does not conflict with the other aircraft s intentions in response to the same conflict5. ATS surveillance (air) The ADS-B application of VDL Mode 4 can be used with ground stations to provide ATS surveillance either as an alternative to radar or working in conjunction with existing radar systems. During a transition phase, there will be mixed coverage of ADS-B and radar surveillance. Track data based on ADS-B; radar or merged (fused) ADS-B/radar data is presented on ATS displays. The quality of ADS-B data (based on precise GNSS position and course information) information is superior to radar-only data and therefore provides a better basis for predictions made by the ground system. This capability is further enhanced by the supplementary intent information in ADS-B reports. Surface movement surveillance (& Navigation) Advanced Surface Movement Guidance and Control System (A-SMGCS) will become an essential means for maintaining maximum capacity and safety in low visibility conditions at high-density airports. VDL Mode 4 provides a flexible communication, surveillance and navigation backbone which supports the creation and operation of A-SMGCS, providing for example: ADS-B data to support the ground movement surveillance system; ADS-B combined with CDTI for support of guidance on the ground, surface navigation, situational awareness, and collision avoidance; a two-way data link to support automated controller-pilot communications; up linked GNSS augmentation to support aircraft navigation in poor visibility; a communication link to assist airline operators in the surveillance and control of support vehicles. Search and Rescue (SAR) In Search And Rescue (SAR) operations, VDL Mode 4 services could be used to provide surveillance services to support, for instance: provision of an overall situation display to support SAR activities and coordination of resources including participating vessels; point out last known position from disabled aircraft or vessel; aid to visual acquisition; separation assurance Communication applications Standardisation effort is ongoing within the industry for the applications described below: Controller-pilot data link communications (CPDLC)

21 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 21 Controller Pilot Data Link Communication (CPDLC) illustrated in Figure 3-1 is an ATN function providing point-to-point communications of time-critical data between pilots and controllers. Departure clearance (DCL) DLC could be described as a variant of CPDLC for semi-automated data link exchange of messages between an aircraft and the control tower (TWR) prior to commencement of taxiing for take-off. Flight Information Services (FIS) FIS is a ground-generated communication function that provides time sensitive weather and supporting information to the aircraft. Although the information can be carried via the pointto- point services provided by the ATN services of VDL Mode 4, an alternative and more efficient method is to broadcast such information to all users using the broadcast services of VDL Mode Navigation applications GNSS augmentation When using GNSS data for navigation or surveillance, a GNSS augmentation system is required to ensure the quality of the position data. Combined with a GNSS reference system for computing differential corrections and integrity data for satellites in view of the ground station, VDL Mode 4 can be used to broadcast a differential GNSS signal using the GNSS augmentation. Air and ground mobile users can receive differential GNSS augmentation signals when a VDL Mode 4 ground station is within line-of-sight. This augmentation provides navigation application, which is complementary to GBAS. Service for wider geographical area can be provided through a network of ground stations, which are connected through a ground network, typically located at airports would extend the coverage of the augmented system. The network could be used for monitoring of the operation and possibly for exchange of information between individual stations in order to further enhance the integrity of the broadcast augmentation data. The augmented network could be expanded indefinitely. Overall objective is to achieve complementary systems that can support navigation in all phases of flight for gate-to-gate operation including A-SMGCS. Galileo is a component of GNSS for augmentation and therefore would be used as a complementary component to provide navigation during the various phases of flight. In order to achieve this functionality and implement it on a large scale, standardisation of this architecture and generation of standards would be required. This approach is currently not under consideration within the standardisation organisations such as Eurocae, ICAO etc Secondary Navigation in VDL Mode 4 based on triangulation VDL Mode 4 is capable of providing navigation without GNSS signals as a backup or fallback function in case of primary navigation failure in the GNSS receiver or GNSS signal. The secondary navigation function, which is defined as an optional element within the SARPs for VDL Mode 4, provides for navigation to en route accuracies (RNP 1) without reliance on

22 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 22 GNSS. In remote/oceanic airspace, a user with a failed GNSS receiver can navigate successfully by relying on the UTC-synchronised Mode 4 synchronisation bursts of other users in the airspace (who determine their own position and accurate time either via GNSS or other system with similar performance). In domestic airspace, the secondary navigation function allows a civil aviation authority to use its VDL Mode 4 ground infrastructure as a backup to GNSS. This assumes a stable source of time is available to the associated groundbased radios. The secondary navigation concept is similar to that of GNSS, illustrated in Figure 2-5. In GNSS, pseudo-noise (PN) ranging signals transmitted by the GNSS spacecraft are slaved to Universal Co-ordinated Time (UTC). These signals emanate from known points in space since the ephemeredes of the spacecraft are known. The arrival times of the signals at a GNSS receiver are measured relative to the local clock of the receiver. If the GNSS receiver is synchronised to UTC, the signal flight time (propagation time) divided by the speed of light yields the range to spacecraft, which generated the signal. If the GNSS receiver is not synchronised to UTC, the apparent propagation time yields a so-called "pseudorange". In the general case the receiver is not synchronised, and must solve for its (x, y, z) position as well as its clock offset. These four unknowns can be determined if four measurements with good relative geometry are available. If more than four measurements are available, the system is over determined and can be solved with reduced error and redundancy. The key elements of GNSS are: a set of transmitting platforms at known locations which transmit time-synchronised ranging signals, in sufficient numbers to provide a minimum of four ranging signals with good geometry to the user community with high probability; user equipment able to receive and measure the arrival times of these signals, and performs the necessary computations to triangulate its own position. The fact that the transmitting platforms are moving at orbital speeds is not significant, as long as their paths of motion are known with high accuracy and their locations at any instant of time can be determined to within a few meters. GNSS performs well because the signals are synchronised with great accuracy; the positions of the transmitting satellites are measured and reported with great accuracy, and the ranging signals have sufficient bandwidth to allow highly accurate measurement of arrival time. The key elements of a position determination system are available through the VDL Mode 4 as well: (1) numerous transmitting stations reporting their position with fair accuracy; and (2) time-synchronised signals from these same platforms. In the case of VDL Mode 4, the transmitting stations of interest for secondary navigation are those aircraft or ground stations that report that they are time-synchronised, and whose reported positioning figure of merit is good. Figure 2-6 illustrates the basic concept, which parallels that of GNSS.

23 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 23 GNSS S 1 (P 1, dt 1 ) GNSS S 2 (P 2, dt 2 ) GNSS S 3 (P 3, dt 3 ) GNSS S 4 (P 4, dt 4 ) R 1 R 2 R 3 R 4 P = (x, y, z) t = t UTC = t i + dt i signal flight time = m i + dt 0 - t i - dt i (P 0, dt 0 ) Satellite positions determ ined from ephem erides Satellite U TC clock offsets also read from m sgs Pseudoranges (R i ) found relative to local clock U ser position (P 0 ) and clock (dt 0 ) are calculated Figure 2-5 Overview of GNSS Navigation Concept The position solution determined through the VDL Mode 4 that will be less accurate than that of GNSS for the following reasons: 1. In most cases, the uncertainty in the reported position of a user is larger than the uncertainty in the reported position of a GNSS satellite; 2. The transmissions are emitted with greater time jitter and uncertainty than the transmissions of a GNSS satellite; and 3. The arrival time measurements at a receiving station are not as precise as the arrival time measurements performed in a GNSS receiver. Nevertheless, a position solution can be generated. The draft SARPs for VDL Mode 4 specify transmit timing jitter 1 usec (2σ). This corresponds to a range uncertainty of 300 m (~1000 ft). If signal arrival times can be measured to equivalent accuracies (approximately 1 usec (2σ)), ranging errors on each signal would be bounded by 500 m (2σ) and users experiencing good geometry would achieve positioning accuracies on the order of 1 km or better. This would be the typical performance for users in active airspace (where many suitably-equipped users would be located in all directions about the user), or users in airspace where the CAA had explicitly designed the ground infrastructure to provide acceptable geometry (a network of ground stations could be completely independent of GNSS, and could provide enhanced performance 2 due to their highly accurate position reports and possibly their more accurate transmit timing). 2 Relative to that achieved via ranging from mobile units.

24 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 24 Requires measurement of sync burst arrival time to a small fraction of a symbol period achievable with careful design User position and time derived from multiple external stations (3 or more) + altimeter expected accuracy ~ 1-2 km System time (w/o position) derived from autonomous nav (Loran, INS,...) plus one external station Similar to GNSS Full backup for GNSS sufficient to maintain communications, and navigate in en route airspace. Figure 2-6 Secondary Navigation in VDL Mode Operational benefits of secondary navigation The operational benefits of secondary navigation are: A backup navigation source for Galileo for conditions where Galileo signals are not available for enroute navigation due to failure, masking or other reasons. A robust means to maintain efficient communications and resource sharing in the VDL Mode 4 protocol. Ability to generate an independent range estimate to a user (i.e., by estimating the propagation time of the received message) supports enhanced integrity features at the MAC layer and above. In domestic airspace, secondary navigation in combination with a ground network which transmits synchronisation bursts on the Global Signalling Channels (GSC) can provide a full GNSS backup suitable for en route navigation. 3 This robust, locally controlled backup may ease the global introduction of GNSS as a primary means of navigation and allows for an early introduction of GNSS navigation using Galileo satellites. Airborne and/or ground stations provide a backup to isolated users with failed GNSS equipment. 3 This requires an independent source of accurate time at the ground stations, and sufficient redundancy of ground stations to provide coverage by 3 or more stations, with high probability, to users at or above a designated altitude

25 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: VDL MODE 4 LOCAL PERFORMANCES The standardisation work at ICAO and other standardisation institutions for CNS services is underway; Table 2-1 shows the expected target performance for the Communication, Navigation and Surveillance services. Only Terminal and APV-I, navigation operation using differential GNSS correction broadcast via VDL Mode 4 data link is considered here. The performance shown here is complementary to the performance provided by GBAS for the services shown in the table. VDL Mode 4 Performance Table 2-1 VDL Mode 4 Target Performance for CNS Services Integrity 1-1 x 10-5 Continuity of Service Communication (FIS-B; Point-to-point) per message x 10-4 per hour Navigation (APV-I) 1-1 x 10-7 per hour 1 5 x 10-5 per hour Surveillance (ADS-B; TIS-B) 1-1 x 10-6 per target Availability x 10-4 per hour MTBO hours hours hours These performance figures are still under development but it can be seen from the open access services of Galileo and VDL Mode 4 that these figures can be achieved easily. The navigation performance would be achieved using differential Galileo signals generated via a network of ground stations as described in section Currently ICAO GBAS SARPs does not specify the use of VDL Mode 4 data link for GBAS for Category I precision approach, however using Galileo and differential Galileo signals the navigation performance shown in Table 2-1 could be achieved. Spectrum planning which is an ongoing process at ICAO currently supports the use of VDL Mode 4 in the aeronautical navigation band for surveillance only; hence additional institutional issues are required to be addressed for this concept to be implemented. 2.4 VDL MODE 4 COVERAGE The planned service volume (range) is 200 NM air-to-air, air-to-ground and ground-to- air. When the load on the channel exceeds 90% then the service volume (or cell ) around a user shrinks as described in Figure 2-8. (The Robin Hood principle). However, the minimum cell size is 150 NM, and the transmission rate is always kept constant out to the edge of the cell. The Robin Hood principle allows a station operating on a busy channel to use slots previously reserved for broadcast transmission by another station as long as slots reserved by the most distant stations are chosen in preference to those of nearer stations. This results in a graceful reduction in the broadcast range of a station on busy channels as illustrated in Figure 2-8

26 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 26 Figure 2-7 shows the 200 nm coverage distance in actual flight tests conducted at the Stockholm/Arlanda airport. The results were similar for both air to air and air to ground broadcasts. Figure 2-7 VDL Mode 4 Coverage from Flight Test at Stockholm/Arlanda Airport Figure 2-8 Illustration of Cell Shrinkage using Robin Hood principle 2.5 VDL MODE 4 TRANSCEIVER ASPECTS VDL MODE 4 TRANSCEIVER The VDL Mode 4 system is a transponder that provides for a number of transmitters and receivers capable of transmitting at any 25 khz channel in the MHz band and receiving at any 25 khz channel in the MHz band. Typically the system consists of one transmitter and two receivers where the signal transmission and reception is

27 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 27 via one transmit and one receive VHF antenna. It is possible to use one antenna interface for transmitting and receiving. The GNSS subsystem of a VDL Mode 4 transponder also accommodates one GNSS antenna interface that functions as interface to the GNSS Signal in Space and a GNSS subsystem. The GNSS system could be based on Galileo or GPS or a combination of GPS and Galileo. The GPS component of the hybrid transreceiver would comply with the existing ICAO, Eurocae and other international aviation organisation s specifications and standards. The GNSS subsystem is used for both Navigation and Surveillance. Enroute and terminal navigation operations are performed using GNSS based positioning data. Precision approach is performed using differential GNSS signals. GNSS based position reporting is used for ADS broadcast for surveillance functions. The transponder has the capability to receive data on multiple VHF channels and transmit on one channel simultaneously. A single transmitter can typically report on several VHF channels by changing channels between transmissions. This feature provides full ADS-B reporting and monitoring capability. Figure 2-9 shows a block diagram of a typical VDL Mode 4 transponder. The transponder typically contains one transmitter and two receivers. The embedded computation subsystem performs all the software necessary to perform the necessary STDMA, slot allocation and other control of the transmitters and receivers to perform the VDL Mode 4 functions as described in section 2. The embedded computer also process the GNSS data for interface with the external equipment for Navigation and Surveillance functions. The computation block would also perform the input/output interface and control with the external equipment. It should be noted that within the computation block the processing of the Communication, Navigation and Surveillance functions are partitioned such that the failure of one function does not affect the operation of the other function. Brick wall partitioning is implemented along with extensive safety analysis to ensure that the partitioning is robust and no common mode failures exist.

28 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 28 GNSS Receiver External Interface Input VHF Transmitter VHR Receiver Computation Subsystem External Interface Output VHF Receiver Figure 2-9 Block Diagram of a Typical VDL Mode 4 Transceiver for CNS applications The number of transmitters and receivers in a VDL Mode 4 transponder and for an aircraft depend on: the services required, e.g. ADS-B, FIS-B, ATN and non-atn point-to-point communications; Navigation functions for enroute and terminal and augmentation with Galileo for precision approach capability the quality of service (QoS), including possible sharing of channels for different services; the number of aircraft to be supported in a given environment at a given reporting rate. Multiple channels may be needed to accommodate a large number of aircraft. This impacts on the required transceiver configuration. the redundancy and availability of services required In most applications a single VHF antenna for transmitting and receiving is sufficient HYBRID TRANSCEIVER As described in section a VDL Mode 4 system consists of a number of transmitters and receivers, which operate, in the VHF band. Also embedded in the VHF Transponder is a GNSS receiver. This receiver is typically a GPS receiver. As a complimentary system to Galileo the GNSS receiver would be a hybrid receiver. The GPS component of the hybrid receiver would comply with the existing ICAO, Eurocae and other international aviation organisation s specifications and standards. The hybrid GNSS receiver would also comply with the ICAO, Eurocae and other international specifications and standards for aviation that would be developed.

29 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 29 The hybrid receive would contain the functionality of a Galileo receiver. This receiver would be able to track and decode the navigational ranging signals. These signals would be used to primarily compute Position, Velocity and Time and other navigational parameters. A GPS receiver and an EGNOS receiver will also augment the Galileo receiver and other navigation GNSS signals such as WAAS etc. could also be included in the Hybrid receiver, reference figures Figure 2-10and Figure Within the VDL Mode 4 transponder there is computational capability provided to compute the best possible navigation solution based on the characteristics of the raw ranging signals. Because of the multiplicity and redundancy of navigational signals which include VDL Mode 4 (described in section 2.1) as a backup navigational source a navigation solution which has high integrity and accuracy better than that of standalone GPS with virtually 100% availability and a high continuity of function is provided. Improvement in performance due to the different components of the hybrid receiver is shown in Table 3-1. This table shows how the VDL Mode 4 and Galileo complement each other and bringing benefits to each other along with a method for early implementation of Galileo. Galileo Receiver GPS Receiver EGNOS Receiver Other GNSS Receivers Best Navigation Solution External Interface Input VHF Transmitter Computation Subsystem External Interface Output VHF Receiver VHF Receiver Figure 2-10 Detailed Hybrid GNSS Transceiver

30 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: Spectrum for Hybrid Transceiver As shown in Error! Reference source not found. VDL Mode 4 for aviation use operates in the aeronautical VHF spectrum band, i.e MHz, Galileo ranging signals for open access are broadcast on L1, E5a and E5b band. The masks defined for VDL Mode 4 equipment should prevent any harmonics or interference signals being generated that would cause problems to the Galileo or Hybrid receiver. Conversely the Galileo and Hybrid receivers should be so designed to have immunity similar to that defined currently for GPS receivers. VDL Mode 4 Galileo Signals E5A/E5B E6 108 MHz MHz E2 L1 E MHz 1215 MHz 1260 MHz 1300 MHz 1559 MHz 1591 MHz Figure 2-11 VDL Mode 4 and Galileo Spectrum Allocation

31 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 31 3 COMBINATION IN CRITICAL ENVIRONMENT 3.1 CRITICAL ENVIRONMENT Critical environment considered for CNS applications are areas where the CNS functions are limited. These limitations are due to various reasons, such as terrain, limited space, high traffic volume, interference, lack of radar or radar coverage etc. 3.2 VDL MODE 4 AND GNSS IN CRITICAL ENVIRONMENT The Surveillance function of ADS-B service and Navigation are interdependent for which VDL Mode 4 and Galileo form a complementary system. ADS-B- as defined, developed and tested within several EC projects such as NEAN, NEAP, NUP, MEDUP, MFF, comes as a service bundled with VDL Mode 4 when augmented with Galileo as described here builds on this inter-dependence and bundling. These programs demonstrate that the VDL Mode 4 and GNSS form complimentary systems where timing and navigation redundancy is provided by each system allows for continuos operation in areas where signals are interrupted due to terrain, interference and other critical environmental situations. It should be noted that the overall objective of airport authorities and service providers is to be able to provide navigation capability for a full up gate to gate operation. New technologies are investigated and exploited to ensure that these operations can be achieved to the extent possible as well as to provide full performance in Critical Environment. The sections below describe VDL Mode 4 and augmentation components in the Galileo context. The objective of this is to propose a comprehensive and homogenous approach rather than dealing with the VDL Mode 4 and augmentation components as independent Local Components. The systems being interoperable combine assets of different European development programs into an integrated approach for Aviation Users. Some of these programs are the Mediterranean Update Programme (MEDUP) and Mediterranean Free Flight (MFF) programme. 3.3 EXTENSION TO GALILEO BRIEF DESCRIPTION OF VDL4- AUGMENTATION WITH GNSS VDL Mode 4 can be augmented with GNSS including Galileo to provide a service that provides GNSS augmentation data to mobiles in all user groups of the aeronautical transport sector. This augmentation can be extended by a network of ground stations that provide this augmentation. The overall long term objective of this augmentation is toto support all user groups and all phases of operation. The requirements on accuracy, integrity, alert limit, etc. vary for different operations. In order to use the VDL Mode 4 efficiently, different operational service levels have been considered each intended for different operations and/or applications. Such a service could provide an enhancement of performance whereby VDL

32 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 32 Mode 4 and Galileo complement each other. This augmentation concept has been extensively tested in EC projects such as NEAN, NEAP and NUP. Tests were led by Sweden and are currently being also tested in the MEDUP and MFF programs. A VDL Mode 4- system, which provides GNSS augmentation service by which the user receives information directly from ground-based transmitters, allows continuous reception of the service over a large geographical area (200NM+). The ground components may be interconnected in a network. This network is basically made up of multiple ground stations with overlapping coverage. The stations are networked together in order to provide coverage over a larger area than that provided by a single ground station. Such a network can be used in: High latitude locations Gate-to-gate surveillance and navigation operation for aviation Global Coverage Is unencumbered by Institutional issues Provides Redundancy Reduction of Liability due to Redundancy VDL-4 is a particularly effective communication link for multiple CNS (Communication, Navigation, and Surveillance) applications, such as ADS-B, FIS-B, TIS-B, A-SMGCS, and CPDLC. Therefore, it is expected that most high value air traffic will be within reach of one or more VDL-4 Ground Stations whenever these aircraft are near land. As a result, VDL4- augmentation will be able to provide high accuracy and high integrity GNSS for all such traffic. In addition, the same accuracy and integrity will be available for Surface Movement Guidance and Control of aircraft and of support vehicles at any airport equipped with a VDL-4 Ground Station. When integrating multiple services such as Communication, Navigation and Surveillance in a single system, care must be taken in partitioning and appropriate system and safety analysis should be performed to ensure no single point or common cause failures exist and the reliability and integrity of each service meets the specification. The liability issue, which is associated with loss of service due to the failure of the primary system, without a backup system of equivalent performance. VDL Mode 4 and Galileo provide a reduction in liability by providing complimentary backup to secondary timing and navigation for each other VDL4-AUGMENTATION WITH GALILEO FOR AVIATION Galileo and its potential Local Components provides the navigation service delivering high precision and integrity service to the users. In aviation, this service will be utilised by the surveillance function to provide an accurate position with high integrity. This inter-relation between the navigation and surveillance services and systems is critical and is addressed in this section.

33 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 33 Automatic Dependant Surveillance Broadcast (ADS-B) is a surveillance function that will use Galileo and its Local Components and is generally seen as an enabler for true growth of capacity and increased safety in European Airspace. The purpose of VDL4-augmentation is to provide greatly enhanced GNSS surveillance and navigation accuracy and integrity throughout any region served by VDL-4. As a direct result, the performance of ADS-B over the VDL-4 data link will also be enhanced because of the improved GNSS accuracy and integrity provided by the Galileo component. Galileo augmentation of VDL4 provides improved GNSS accuracy, integrity and availability. The multiple applications inherently requires different service levels, since the requirements for en-route navigation is very different from approach or surface movement applications. The different service levels are discussed in the next section. Enhanced VDL4-augmentation using GPS and Galileo satellite navigation system will be designed to allow support for: All phases of flight (seamless gate-to-gate) some of the gate-to-gate operations may need additional augmentation; Multiple service levels to support the above; Multiple applications down to non-precision approach with vertical guidance (APV-I and II) and Advanced Surface Movement Guidance and Control (A-SMGCS) and; For all user groups. Table 3-1 shows the improvement in performance when VDL 4- is augmented by GNSS as a progression when the GNSS complement is changed from GPS to Galileo and GPS + Galileo hybrid. Since the specifications are still under development, the exact quantification of performance figures is not feasible currently. However, it can be easily seen that there is an improvement in accuracy by the use of Galileo instead of GPS and there is a considerable improvement in availability by the combined use of GPS and Galileo. VDL Mode 4 being able to be used as a secondary navigation source as described in section 2.2 additionally compliments this improvement. Figure 3-2 shows an actual VDL Mode 4 Airborne Transceiver and Ground Station used for Communication, Navigation and Surveillance as part of NEAN Update Program. These systems are currently operational in Sweden, Germany, France and Denmark.

34 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 34 Figure 3-1 Basic VDL4-Augmentation with Galileo Concept Table 3-1 VDL4-Augmentation Performance Improvement progression Performance Parameters Accuracy (2dRMS) Augmentation using GPS Augmentation using Galileo Augmentation using GPS + Galileo <10 m + = Availability (%) Integrity Time to Alarm Secondary Navigation Reduction of Liability 6 sec = =

35 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 35 VDL4 CNS Ground station VDL4 Airline transponder VDL4 General Aviation transponder Figure 3-2 VDL Mode 4 Airborne and Ground Subsystem for CNS/ATM

36 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: VDL4-AUGMENTATION WITH GALILEO FOR MULTIMODAL APPLICATIONS VDL Mode 4 and GALILEO play an important role in multimodal applications involving Aviation, Maritime and Land applications. Search and rescue is an example of a multimodal application, which could be envisaged through VDL Mode 4. Intermodal is defined as transportation using at least two modes of conveyance without change of container. Multimodal is defined as transportation using at least two modes of conveyance, allowing a shipment to change between conveyance container (e.g. Air Cargo). Examples of Applications are: Real time origin - destination tracking of containers and swap bodies Remote monitoring of container seal integrity, esp. for high value goods Monitoring of shipment condition (perishables and dangerous goods) Telematics & fleet management Search and Rescue Benefits include: More accurate and timely dispatch of resources Increased transparency of Supply Chain Less production disruptions in JIT / sequenced deliveries Higher Security => lower insurance premiums More effective and efficient tracking & tracing System requirements for intermodal and multimodal applications include: Easy to use, easy data access Protection of sensitive / proprietary information Robust & reliable Tamper proof Low investment Low operating costs Global coverage Integration of mode specific information (e.g. UIC) Open system architecture More than tracking capability Universal Automatic Identification System for Maritime The emerging ship and shore-based broadcast system within Maritime is called Universal AIS (or AIS, as it is commonly known).

37 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 37 AIS uses the STDMA technology which is also used by VDL Mode 4 although it is simpler in general. It uses a lower baud rate, less protocols etc. VDL Mode 4 is the more advanced generation of STDMA/AIS. Clearly, the close relationship facilitates multimodal solutions. AIS includes the Navigation and surveillance piece, i.e. GNSS Augmentation and Position broadcast (including identification), a variant of ADS-B for ship. In the maritime world it is usually referred to as Ship to Ship and Ship to Shore. AIS also supports communication of short messages between ships. A user interface with a digital moving map provides improved navigation capability as well as situational awareness by showing other equipped ships. An AIS station is a VHF radio transceiver capable of sending ship information such as identity, position, course, speed, length, ship type and cargo information etc., to other ships and to suitable receivers ashore. Information from an operational shipboard AIS unit is transmitted continuously and automatically without any intervention of the ship s staff. When used with an appropriate graphical display, shipboard AIS enables provision of fast, automatic and accurate information regarding risk of collision by calculating Closest Point of Approach (CPA) & Time to Closest Point of Approach (TCPA) from the positional information transmitted by target vessels. Therefore, AIS will become an important supplement to existing navigational systems, including radar. In general, data received via AIS will enhance the quality of information available to the ship's staff. AIS is an important tool to enhance the awareness of the traffic situation for all users. Purpose The purpose of AIS is to: identify vessels, assist in target tracking, simplify and promote information exchange, Use of AIS The International Maritime Organisation (IMO) specifies three main applications for AIS: 1. Ship to ship, for collision avoidance. 2. For littoral states, in order to obtain information about ships and their cargoes. 3. As a VTS tool, for traffic management. AIS is an additional source of navigational information. AIS supports, but does not replace navigational systems such as radar target tracking and VTS. In general, AIS tracking offers the following significant benefits: highly accurate information, provided in near real-time, capable of instantaneously presenting target course alterations,

38 Complementary Systems: VDL Mode 4 ISSUE : 1.1 PAGE: 38 not subject to target swap, not subject to target loss in clutter, not subject to target loss due to fast manoeuvres, and ability to look around bends and behind islands. Furthermore, AIS can: look behind the bend in a channel or behind an island in an archipelago, to detect the presence of other ships and identify them. predict the exact position of a meeting with other ships in a river or in an archipelago. know which port and which harbour a ship is bound for know the size and the draft of ships in the vicinity. detect a change in a ship s heading almost in real time identify a ferry leaving the shore bank in a river. Figure 3-3 Overview of the AIS