Report on the Validation of the Requirements in the SARPs for UAT

Transcription

1 International Civil Aviation Organization 999 University Street Montreal, Quebec, Canada H3C 5H7 Report on the Validation of the Requirements in the SARPs for UAT Revision April 2005 Prepared by: ACP WG-C UAT Subgroup

2 Change Record Date/Version Change Original Draft based on Version 3.1 of the draft UAT SARPS, in preparation for review 8 September 2004/v0.1 of the UAT Subgroup Meeting #6 in Madrid, September 2004 Incorporating modifications as agreed to during the UAT Subgroup Meeting #6 in 17 September 2004/v0.2 Madrid, September 2004 As reviewed and agreed to during the meeting of the ICAO ACP WG-C/8 in Munich, 21 1 November 2004/v1.0 September No further comments were received against the v0.2 version presented in Munich as of the action item deadline of 31 October As reviewed and updated during the UAT Subgroup Meeting #7 in Montreal, November 2004/v1.1 November 2004 As modified in preparation for review for the UAT Subgroup at Meeting #8 at DFS in 25 January 2005/v1.2 Langen, Germany, 1/31/05 2/2/05 As modified during the review of all Working Papers during the UAT Subgroup Meeting #8 at DFS in Langen, 1/31/05 2/2/05, including changes that were agreed upon by the UAT Subgroup with respect to suggested changes by the Secretariat in UAT-SWG08-31 January 2005/v1.3 WP20, and included insertion of Transmit Power levels, requirements for Mandatory Carriage Requirements and moving Appendix A to the Manual on the UAT Detailed Technical Specifications. As modified in preparation for the review for the UAT Subgroup at Meeting #9 in Montreal 28 February through 2 March Includes insertion of a paragraph on the 23 February 2005/v1.4 asymmetry in and completion of references for unit testing in and As modified during the review by the UAT Subgroup in Meeting #9 in Montreal, 28 2 March 2005/v1.5 February 2 March March 2005/v1.6 As modified during the review by the UAT Subgroup in Meeting #10 in Montreal, March April 2005/V2.0 As reviewed and approved by ACP WG-C during their Meeting #9 in Montreal, 4 8 April

3 12.0 CHAPTER 12. VALIDATION OF UNIVERSAL ACCESS TRANSCEIVER (UAT) Validation of Definitions and Overall System Characteristics Validation of Definitions Validation of UAT Overall System Characteristics of Aircraft and Ground Stations Validation of Transmission Frequency Validation of Frequency Stability Validation of Transmit Power Validation of Transmit Power Levels Validation of Maximum Power Validation of Transmit Mask Validation of Spurious Emissions Validation of Polarization Validation of Time/Amplitude Profile of UAT Message Transmission Validation of Mandatory Carriage Requirements VALIDATION OF SYSTEM CHARACTERISTICS OF THE GROUND INSTALLATION Validation of Ground Station Transmitting Function Validation of Ground Station Transmitter Power Validation of Ground Station Receiving Function VALIDATION OF SYSTEM CHARACTERISTICS OF THE AIRCRAFT INSTALLATION Validation of Aircraft Transmitting Function Validation of Aircraft Transmitter Power Validation of Receiving Function Validation of Receiver Sensitivity Validation of Long UAT ADS-B Message as Desired Signal Validation of Basic UAT ADS-B Message as Desired Signal Validation of UAT Ground Uplink Message as desired signal Validation of Receiver Selectivity Validation of Receiver Desired Signal Dynamic Range Validation of Receiver Tolerance to Pulsed Interference VALIDATION OF PHYSICAL LAYER CHARACTERISTICS Validation of Modulation Rate Validation of Modulation Type Validation of Modulation Distortion Validation of Broadcast Message Characteristics Validation of UAT ADS-B Message Validation of Bit Synchronization Validation of The Message Data Block Validation of FEC Parity Validation of Code Type Validation of Transmission Order of FEC Parity Validation of UAT Ground Uplink Message Validation of Bit Synchronization Validation of Interleaved Message Data Block and FEC Parity Validation of Message Data Block (before interleaving and after de-interleaving) Validation of FEC Parity (before interleaving and after de-interleaving)

4 Validation of Code Type Validation of Transmission Order of FEC Parity Validation of Interleaving Procedure GUIDANCE MATERIAL List of Figures Figure 1: UAT Transmit Spectrum Figure 2: Time/Amplitude Profile of UAT Message Transmission Figure 3: Ideal eye diagram Figure 4: Distorted eye diagram List of Tables Table 1: Transmitter Power Levels... 9 Table 2: UAT Transmit Spectrum Table 3: Standard Receiver Rejection Ratios Table 4: High Performance Receiver Rejection Ratios Table 5: Validation of FEC Parity Table 6: Ground Uplink Interleaver Matrix

5 12.0 CHAPTER 12. VALIDATION OF UNIVERSAL ACCESS TRANSCEIVER (UAT) 12.1 Validation of Definitions and Overall System Characteristics Validation of Definitions UAT: Universal Access Transceiver (UAT) is a broadcast data link operating on 978 MHz, with a modulation rate of Mbps. UAT ADS-B Message: UAT ADS-B Messages are broadcast once per second by each aircraft to convey state vector and other information. UAT ADS-B Messages can be in one of two forms depending on the amount of information to be transmitted in a given second: the Basic UAT ADS-B Message or the Long UAT ADS-B Message (see Section for definition of each). UAT Ground Stations can support Traffic Information Service-Broadcast (TIS-B) through transmission of individual ADS-B Messages in the ADS-B segment of the UAT frame. UAT Ground Uplink message: The UAT Ground Uplink Message is used by Ground Stations to broadcast, within the Ground Segment of the UAT Frame, flight information such as text and graphical weather data, advisories, and other aeronautical information, to aircraft that are in the service volume of the Ground Station (see Section for further details). Standard Receiver: A general purpose UAT receiver satisfying the minimum rejection requirements of interference from adjacent frequency Distance Measuring Equipment (DME) (see Section for further details). High Performance Receiver: A UAT receiver with enhanced selectivity to further improve the rejection of adjacent frequency DME interference (see Section for further details). Optimum Sampling Point: The optimum sampling point of a received UAT bit stream is at the nominal center of each bit period, when the frequency offset is either plus or minus khz. Power Measurement Point (PMP): A cable connects the antenna to the UAT equipment. The PMP is the end of that cable that attaches to the antenna. All power measurements are considered as being made at the PMP unless otherwise specified. The cable connecting the UAT equipment to the antenna is assumed to have 3 db of loss. Successful Message Reception (SMR): The function within the UAT receiver for declaring a received message as valid for passing to an application that uses received UAT messages. See Section 4.0 of the Manual on the UAT Detailed Technical Specifications for a detailed description of the procedure to be used by the UAT receiver for declaring successful message reception. 5

6 Pseudorandom Message Data Blocks: Several UAT requirements state that performance will be tested using pseudorandom message data blocks. Pseudorandom message data blocks should have statistical properties that are nearly indistinguishable from those of a true random selection of bits. For instance, each bit should have (nearly) equal probability of being a ONE or a ZERO, independent of its neighboring bits. There should be a large number of such pseudorandom message data blocks for each message type (Basic ADS-B, Long ADS-B or Ground Uplink) to provide sufficient independent data for statistical performance measurements. See Section 2.3 of the Manual on the UAT Detailed Technical Specifications for an example of how to provide suitable pseudorandom message data blocks. Service Volume: A part of the facility coverage where the facility provides a particular service in accordance with relevant SARPs and within which the facility is afforded frequency protection. Validation Acronyms: I A Inspection using common IT Integration Test knowledge I BB Inspection through use of prior analysis/documents A Analysis FT Flight Test S Simulation MN Monitoring UT Unit Test MD Manufacturer s Data NVR No Validation Required (may include editorial inspection) There is no validation required for the above statement of definitions Validation of UAT Overall System Characteristics of Aircraft and Ground Stations Note: Details on technical requirements related to the implementation of UAT SARPs are contained in the Manual on the UAT Detailed Technical Specifications. The UAT Implementation Manual provides additional guidance material Validation of Transmission Frequency The transmission frequency shall be 978 MHz. 6

7 Validation Methods = I BB The use of a single common global channel is the simplest architecture for supporting ADS-B seamless air-to-air operation. As a result, the channel should be of significant bandwidth to assure adequate capacity and performance. The 978 MHz frequency was selected because of the wide channelization that currently exists there and the potential availability of the channel on a global basis. The design of the Universal Access Transceiver was originally proposed in a document entitled A Prototype Transceiver for Evaluating a Multipurpose Broadcast Data Link Architecture captured in RTCA: UAT-WP The rationale for choosing the specific transmission frequency of 978 MHz was further demonstrated in the following Working Papers: RTCA: UAT-WP-2-05, RTCA: UAT-WP-2-14, RTCA: UAT-WP-5-13, RTCA: UAT-WP-5-15, RTCA: UAT-WP-7-11, RTCA: UAT-WP-8-06, RTCA: UAT-WP-8-09, RTCA: UAT- WP-9-10, RTCA: UAT-WP and UAT-SWG04-WP02. These papers provided and supported the following rationale: 978 MHz provides adequate frequency separation from 1090 MHz replies from co-sited SSR transponders and from 1030 MHz interrogations from co-sited ACAS. 978 MHz is in a part of the radionavigation band where transmissions from legacy systems (DME) are from the ground only. This offers the ATCS service provider a reasonable control of nearby interfering sources through the shifting of affected assignments. 978 MHz minimizes interaction of UAT on DME ground transponders since these do not receive in this portion of the band. 978 MHz is the least utilized frequency for operational DME/TACAN systems on a worldwide basis. The ICAO ACP WG-C UAT Subgroup has performed additional analysis on the suitability of 978 MHz to support UAT operation on a worldwide basis. The DFS proposed frequency planning criteria for enroute operations at the fourth meeting of the UAT Subgroup that would support unrestricted assignment of DMEs on the first adjacent channel to 978 MHz. Further analysis was performed for a terminal/approach scenario that confirmed the DFS proposed frequency planning criteria for these types of operations as well. In May 2004 the ICAO NSP Spectrum Subgroup reported that After having noted the results of extensive German (ICAO SSG WP11 UAT Impact on DME-Proposal for Frequency Planning Criteria, IP1, UAT impact on DME-compatibility measurement description and results ) and US studies (ICAO SSG WP6 DME Operation in the Presence of UAT Signals ), the ICAO NSP Spectrum-Subgroup agreed to recommend that UAT/DME channel planning criteria to support future high-level UAT environments specify that the closest assignable DME interrogator receiver frequencies relative to the UAT frequency of 978 MHz are the first adjacent DME channels. 7

8 The ICAO Secretariat consulted with the ITU as to whether the current ITU regulatory framework for the band 960 to 1164 MHz provides for the use of UAT. In November 2003, the ITU indicated that the basic function of ADS-B can be considered as an application within the aeronautical radionavigation service. The ITU further indicated that the functions associated to the UAT ground uplink message are of a nature which would fall into the category of an application in the aeronautical mobile (R) service, and that it would be advisable to change the Table of Frequency Allocations at WRC-07, in the frame of Agenda Item 1.6, to have the ground uplink function of the UAT to operate in a consistent regulatory framework. ICAO (WG-F of ACP) is developing a position for WRC-07 consistent with this ITU advice Validation of Frequency Stability The radio frequency of the UAT equipment shall not vary more than ±0.002% (20 PPM) from the assigned frequency. Validation Methods = I A, I B, B UT Measurements taken on UAT avionics certified to the United States Federal Aviation Administration (FAA) Technical Standard Order (TSO) C154, and on prototype Class A3 Transmitters, have demonstrated compliance to this requirement. See ACP WG-C UAT Subgroup Working Papers UAT-SWG06- WP14, UAT-SWG07-WP03, UAT-SWG07-WP12, UAT-SWG08-WP15, UAT- SWG08-WP16, UAT-SWG08-WP21, and UAT-SWG08-WP Validation of Transmit Power Validation of Transmit Power Levels UAT equipment shall operate at one of the power levels shown in Table 1 below. 8

9 Table 1: Transmitter Power Levels Transmitter Type Minimum Power at PMP Maximum Power at PMP Aircraft (Low) 7.0 watts (+38.5 dbm) 18 watts (+42.5 dbm) Aircraft (Medium) 16 watts (+42 dbm) 40 watts (+46 dbm) Aircraft (High) 100 watts (+50 dbm) 250 watts (+54 dbm) Ground Station (Specified by the service provider to meet local requirements within the constraint of Section ) Note: The 3 different levels listed for the avionics are available to support applications with varying range requirements. See the discussion of UAT aircraft Equipage Classes in Section of the UAT Implementation Manual. Validation Methods = I B, B UT, A Measurements taken on UAT avionics certified to the United States Federal Aviation Administration (FAA) Technical Standard Order (TSO) C154, and on prototype Class A3 Transmitters, have demonstrated compliance to this requirement. See ACP WG-C UAT Subgroup Working Papers UAT-SWG07- WP12, UAT-SWG08-WP15, UAT-SWG08-WP16, UAT-SWG08-WP21, and UAT-SWG08-WP Validation of Maximum Power The maximum EIRP for a UAT aircraft or Ground Station shall not exceed +58 dbm. Note: For example, the maximum EIRP listed above could result from the maximum allowable aircraft transmitter power shown in Table 1 with a maximum antenna gain of 4 dbi. 9

10 Validation Methods = I B, B UT, A Measurements taken on UAT avionics certified to the United States Federal Aviation Administration (FAA) Technical Standard Order (TSO) C154, and on prototype Class A3 Transmitters, have demonstrated compliance to this requirement. See ACP WG-C UAT Subgroup Working Papers UAT-SWG07- WP12, UAT-SWG08-WP15, UAT-SWG08-WP16, UAT-SWG08-WP21, and UAT-SWG08-WP Validation of Transmit Mask The spectrum of a UAT ADS-B Message transmission modulated with pseudorandom Message Data Blocks (MDB) shall fall within the limits specified in Table 1 when measured in a 100 khz bandwidth. Note: Figure 1 is a graphical representation of Table 2. Table 2: UAT Transmit Spectrum Frequency Offset From Center Required Attenuation from Maximum Power Level (db) as Measured at the PMP All frequencies in the range MHz 0 All frequencies in the range MHz Based on linear* interpolation between these points 1.0 MHz 18 All frequencies in the range MHz Based on linear* interpolation between these points 2.25 MHz 50 All frequencies in the range MHz Based on linear* interpolation between these points 3.25 MHz 60 * based on attenuation in db and a linear frequency scale 10

11 UAT Spectral Mask db Below Maximum % Boundary Frequency offset (MHz) Notes: Figure 1: UAT Transmit Spectrum 1. 99% of the power of the UAT spectrum is contained in 1.3 MHz (±0.65 MHz). This is roughly equivalent to the 20 db bandwidth. 2. Spurious emissions requirements begin at ±250% of the 1.3 MHz value, therefore the transmit mask requirement extends to ±3.25 MHz. Validation Methods = I B, B UT, A See ACP WG-C UAT Subgroup Working Paper UAT-SWG04-WP02 that summarizes DFS testing showing that the mask is sufficient to protect adjacent DME for enroute; RTCA Working Paper UAT-WP-8-04A shows that prototype equipment meets the mask and that the mask supports DME and Link 16 compatibility; ACP WG-C UAT Subgroup Working Papers UAT-SWG07-WP12, UAT-SWG08-WP15, UAT-SWG08-WP16, UAT-SWG08-WP21, UAT- SWG08-WP22. These Working Papers show that two of the three prototype Class A3 Transmitters met the UAT SARPs requirements and that the third prototype, Unit #2 missed the spectrum mask by 4 db at a frequency offset of ±3.25 MHz. Although different measurement techniques were used by the laboratories that performed the tests (DFS, United States FAA William J Hughes Technical Center (FAATC) and Rockwell Collins), the test results regarding Unit #1 and Unit #2 were consistent across laboratories, showing that Unit #2, which was tested in the DFS lab, did not meet the requirement. Review by the UAT Subgroup of prototype Unit #3 test results provided by the 11

12 manufacturer led the UAT Subgroup to agree that production UAT Class A3 Transmitters can meet the UAT SARPs requirements. The UAT Subgroup agreed that the testing performed validated the UAT SARPs requirement. ICAO ACP WG-F Meeting 10 Summary Validation of Spurious Emissions Spurious emissions shall be kept at the lowest value which the state of the technique and the nature of the service permit. Note: Appendix 3 of the ITU Radio Regulations requires that transmitting stations shall conform to the maximum permitted power levels for spurious emissions or for unwanted emissions in the spurious domain. Validation Method = I BB Questions were raised regarding requirements on spurious emissions for Universal Access Transceiver (UAT) equipment. The results are found in Working Paper RTCA: UAT-WP-5-14 and ICAO ACP WG-F Meeting 10, Working Paper 22. ICAO ACP Working Group F agreed that the spurious emission boundary for UAT should occur at 250 percent of the 1.3 MHz UAT 20 db bandwidth (i.e., ±3.25 MHz) as indicated in the ICAO ACP WG-F Meeting 10 Summary Validation of Polarization The design polarization of emissions shall be vertical. Validation Method = I A Vertical polarization is preferable to horizontal polarization for a number of reasons, including: The antenna structure for vertical polarization can be relatively simple, consisting of a quarter-wave monopole over a ground plane (the aircraft fuselage). For horizontal polarization the antenna would need to be either a loop-type structure mounted above (or below) the fuselage or 12

13 two half-loops located on either side. For the top-mounted configuration the effect of the fuselage may tend to create a null on the horizon. In either case, the aerodynamic drag of a horizontally polarized antenna is likely to be higher. Nearby TV stations transmit very high power signals (megawatts) using horizontal polarization. Their interference potential will be significantly reduced if the UAT communication signals are vertically polarized. The effects of reflections off the earth (or bodies of water) just above the horizon are likely to be more deleterious for horizontal than for vertical polarization Validation of Time/Amplitude Profile of UAT Message Transmission The Time/Amplitude profile of a UAT Message Transmission shall meet the following requirements, in which the reference time is defined as the beginning of the first bit of the synchronization sequence (see , ) appearing at the output port of the equipment. Notes: 1. All power requirements for subparagraphs a through f below apply to the PMP. For installations that support transmitter diversity, the RF power output on the non-selected antenna port should be at least 20 db below the level on the selected port. 2. All power requirements for subparagraphs a and f assume a 300 khz measurement bandwidth. All power requirements for subparagraphs b, c, d and e assume a 2 MHz measurement bandwidth. 3. The beginning of a bit is ½ bit period prior to the optimum sample point. 4. These requirements are depicted graphically in Figure 2. a. Prior to 8 bit periods before the reference time, the RF output power at the PMP shall not exceed 80 dbm. Note: This unwanted radiated power restriction is necessary to ensure that the UAT Transmitting Subsystem does not prevent closely located UAT receiving equipment on the same aircraft from meeting its requirements. It assumes that the isolation between transmitter and receiver equipment at the PMP exceeds 20 db. b. Between 8 and 6 bit periods prior to the reference time, the RF output power at the PMP shall remain at least 20 db below the minimum power requirement for the UAT equipment class. Note: Guidance on definition of UAT equipment classes is provided in the UAT Implementation Manual. 13

14 c. During the Active state, defined as beginning at the reference time and continuing for the duration of the message the RF output power at the PMP shall be greater than or equal to the minimum power requirement for the UAT equipment class. d. The RF output power at the PMP shall not exceed the maximum power for the UAT equipment class at any time during the Active state. e. Within 6 bit periods after the end of the Active state, the RF output power at the PMP shall be at a level at least 20 db below the minimum power requirement for the UAT equipment class. f. Within 8 bit periods after the end of the Active state, the RF output power at the PMP shall fall to a level not to exceed 80 dbm. Note: This unwanted radiated power restriction is necessary to ensure that the Transmitting Subsystem does not prevent closely located UAT receiving equipment on the same aircraft from meeting its requirements. It assumes that the isolation between transmitter and receiver equipment at the PMP exceeds 20 db. Allowed power range for Equipment Class 20 db Inactive Active Inactive -80 dbm 2 6 T* 6 2 * T = 276 for Short ADS-B T = 420 for Long ADS-B T = 4452 for Ground Uplink ADS-B Message Transmission Interval Time in Bit Periods (1 bit period = 0.96 microseconds) Figure 2: Time/Amplitude Profile of UAT Message Transmission 14

15 Validation Method = I B, B A, MD, UT Appendix B of the UAT Implementation Manual shows that the requirement is adequate; Conclusions of RTCA: UAT-WP-6-08 and RTCA: UAT-WP-8-08; ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP15 summarizes DFS testing on a High Performance Class Transmitter. ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP16 summarizes testing on UAT Transceivers by the FAATC, that have been certified by the United States FAA as per TSO-C154, and Ground Based Transceivers (GBTs) provided by Sensis Corporation that have been accepted as production units by the United States FAA for installation as Ground Stations under the United States FAA Capstone project in Alaska. ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP06 summarizes the test results from Garmin Aviation Technologies certification testing on their GDL-90 UAT Transceiver, certified to FAA TSO-C154. ACP WG-C UAT Subgroup Working Paper UAT-SWG07-WP12, UAT- SWG08-WP21 and UAT SWG08-WP22 summarize the test results from Rockwell Collins with regard to its prototype Class A3 UAT Transmitter Validation of Mandatory Carriage Requirements Requirements for mandatory carriage of UAT equipment shall be made on the basis of regional air navigation agreements which specify the airspace of operation and the implementation timescales for the carriage of equipment, including the appropriate lead time. Note: No changes will be required to aircraft systems or ground systems operating solely in regions not using UAT. 15

16 12.2 VALIDATION OF SYSTEM CHARACTERISTICS OF THE GROUND INSTALLATION Validation of Ground Station Transmitting Function Validation of Ground Station Transmitter Power Recommendation: The effective radiated power should be such as to provide a field strength of at least 280 microvolts per metre (minus 97 dbw/m 2 ) within the service volume of the facility on the basis of free-space propagation. Note: This is determined on the basis of delivering a 91 dbm (corresponds to 200 microvolts per metre) signal level at the PMP (assuming an omnidirectional antenna). The 280 µv/m recommendation corresponds to the delivery of a 88 dbm signal level at the PMP of the receiving equipment. The 3 db difference between 88 dbm and 91 dbm provides margin for excess path loss over free-space propagation. Validation Method = I B, B UT Conclusions in RTCA: UAT-WP-6-08 and ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP16; Unit test results from production UAT GBTs that demonstrate meeting a specified level of performance. UAT Ground Stations broadcasting at the maximum EIRP of 58 dbm will provide the recommended field strength to the radio horizon, assuming free-space propagation loss. However, the desired transmit power for a UAT Ground Station will be established based upon the defined operational service volume Validation of Ground Station Receiving Function Note: An example Ground Station Receiver is discussed in Section 2.5 of the UAT Implementation Manual, with UAT air-to-ground performance estimates consistent with use of that receiver provided in Appendix B of that Manual. 16

17 12.3 VALIDATION OF SYSTEM CHARACTERISTICS OF THE AIRCRAFT INSTALLATION Validation of Aircraft Transmitting Function Validation of Aircraft Transmitter Power The effective radiated power shall be such as to provide a field strength of at least 225 microvolts per metre (minus 99 dbw/m 2 ) on the basis of free-space propagation, at ranges and altitudes appropriate to the operational conditions pertaining to the areas over which the aircraft is operated. Transmitter power shall not exceed 54 dbm at the PMP. Notes: 1. The above field strength is determined on the basis of delivering a 93 dbm (corresponds to 160 microvolts per metre) signal level at the PMP (assuming an omni-directional antenna). The 3 db difference between 225 µv/m and 160 µv/m provides margin for excess path loss over free-space propagation when receiving a Long UAT ADS-B Message. A 4 db margin is provided when receiving a Basic UAT ADS-B Message. 2. Various aircraft operations may have different air-air range requirements depending on the intended ADS-B function of the UAT equipment. Therefore different installations may operate at different power levels (see ). Validation Method = I B, B UT, FT ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP15 summarizes DFS testing on a prototype Class A3 UAT Transmitter developed by Rockwell Collins. ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP16 summarizes testing on UAT Transceivers by the FAATC that have been certified by the United States FAA as per TSO-C154. This Working Paper also includes results of testing on a prototype Class A3 UAT Transmitter developed by Rockwell Collins. ACP WG-C UAT Subgroup Working Paper UAT-SWG07-WP12, UAT- SWG08-WP21 and UAT-SWG08-WP22 summarize the test results from Rockwell Collins with regard to its prototype Class A3 UAT Transmitters. ACP WG-C UAT Subgroup Working Papers UAT-SWG06-WP13 and UAT-SWG06-WP10 provides flight test results consistent with meeting 17

18 this requirement in a given low-density scenario. For further estimated performance, see Appendix B of the UAT Implementation Manual Validation of Receiving Function Validation of Receiver Sensitivity Introductory Discussion of Doppler Effects: During discussions of the testing of the UAT data link versus the testing of other candidate ADS-B data links, the question of Doppler acceleration and its effect on UAT was raised. After further investigation it was concluded that Doppler and Doppler rate do not constitute a performance issue for UAT. The reasons for this are as follows. Doppler will change the frequency and timing of the transmitted signals with respect to the receiver. Under the assumption that the maximum relative velocity of the two receivers is Mach 2, such relative velocity will cause a shift of 2 PPM in the frequency and the timing. Since the UAT carrier frequency is about 1 GHz, the maximum shift under this assumption is about 2 khz. This is operationally insignificant with respect to the 625 khz spacing between a ZERO and a ONE in the UAT waveform. Thus, there is no need to compensate the Doppler, i.e., UAT equipment does not require a tracker. Moreover, since the whole range of frequency variation is similarly negligible, there is no Doppler rate issue as far as frequency shift is concerned. As for the symbol timing issue, during the course of a Long UAT ADS-B Message, which is 420 bits long, a Doppler shift of 2 PPM will cause a timing error of 420* = bit periods. For a UAT Ground Message the timing error could be about 10 times worse (actually less because the ground isn't moving), but it's still less than 0.01 bit periods. That is much less than the errors assumed for the initial synchronization process. This means that UAT does not have to track the symbol (bit) timing. UAT just synchronizes and goes with that timing for the duration of the Message. Any slewing of the Doppler during the reception of a Message from maximum to minimum Doppler will only make things better. Thus, Doppler rate is not a significant factor in symbol timing Validation of Long UAT ADS-B Message as Desired Signal A desired signal level of 93 dbm applied at the PMP shall produce a rate of Successful Message Reception of 90% or better under the following conditions: a. When the desired signal is of nominal modulation (i.e., FM deviation is 625 KHz) and at the maximum signal frequency offsets, and subject to relative Doppler shift at ±1200 knots. 18

19 b. When the desired signal is of maximum modulation distortion allowed in Section , at the nominal transmission frequency ±1 PPM, and subject to relative Doppler shift at ±1200 knots. Note: The receiver criteria for Successful Message Reception of UAT ADS-B Messages are provided in Section 4 of the Manual on the UAT Detailed Technical Specifications. Validation Methods = I B, B UT The rate of Successful Message Reception of 90% for UAT was initially set as the standard based on this figure being accepted as requirements for sensitivity for Transponders and the 1090 MHz Extended Squitter ADS-B data link. The figure of 90% can be found in ICAO SARPs and RTCA MOPS documents as a reference for its inclusion into the first draft of the UAT MOPS, documented in Working Paper RTCA: UAT-WP The Receiver Sensitivity of -93 dbm was originally proposed in the first draft of the UAT MOPS, documented in Working Paper RTCA: UAT-WP Upon review of this document by Working Group 5 (WG-5) of the RTCA Special Committee 186 (SC-186), an action item was generated for further investigation and validation of the value, as documented in the Minutes to UAT MOPS WG-5 Meeting #2, item #6. As a result of this action item, Working Paper RTCA: UAT-WP-3-06 reported on the study and measurement of early prototype UAT Transceivers in order to validate the initially proposed sensitivity of -93 dbm. Further validation efforts by RTCA SC-186 WG-5 produced a simulation environment at Johns Hopkins University Applied Physics Lab which resulted in the report of simulation runs in RTCA: UAT-WP-5-18, which further validates the selection of the sensitivity value of -93 dbm for the Long UAT ADS-B Message. Subsequent measurements of the implementability of this sensitivity on commercially available Garmin GDL 90 UAT Transceivers certified by the United States FAA, and modified Class A3 receiver prototypes is documented in ACP WG-C UAT Subgroup Working Papers UAT-SWG06-WP13, UAT- SWG08-WP06, and UAT-SWG08-WP16. Additional references include ACP WG-C UAT Subgroup Working Paper UAT-SWG06-WP14, and Appendix B of the UAT Implementation Manual. 19

20 Validation of Basic UAT ADS-B Message as Desired Signal A desired signal level of 94 dbm applied at the PMP shall produce a rate of Successful Message Reception of 90% or better under the following conditions: a. When the desired signal is of nominal modulation (i.e., FM deviation is 625 KHz) and at the maximum signal frequency offsets, and subject to relative Doppler shift at ±1200 knots. b. When the desired signal is of maximum modulation distortion allowed in Section , at the nominal transmission frequency ±1 PPM, and subject to relative Doppler shift at ±1200 knots. Note: The receiver criteria for Successful Message Reception of UAT ADS-B Messages are provided in Section 4 of the Manual on the UAT Detailed Technical Specifications. Validation Methods = I B, B UT For any given UAT Receiver, a 93 dbm sensitivity for Long UAT ADS-B Messages (with the FEC as defined in the UAT SARPs), as required above, will provide a 94 dbm sensitivity for Basic UAT ADS-B Messages (with the FEC as defined in the UAT SARPs), assuming that the Bit Error Rate (BER) is independent of the UAT Message Type. The 1 db difference in the Long and Basic UAT ADS-B Messages can further be validated as shown in ACP WG-C UAT Subgroup Working Paper UAT-SWG07-WP03 and RTCA: UAT-WP The first Working Paper shows that for 90% SMR, the Long UAT ADS-B Message needs a channel BER of and the Basic UAT ADS-B Message requires a BER of (less stringent). If you look at the INR=-infinity curves in Figures 3 and 7 of the second Working Paper, you will see that for both of the 1.2 MHz filter and the 0.8 MHz filter (in the Garmin design), the BER difference implies that about 1 db less of desired signal is needed to receive a Basic ADS-B Message than to receive a Long ADS-B Message. Subsequent measurements of sensitivity on commercially available Garmin GDL 90 UAT Transceivers certified by the United States FAA under TSO C154 is documented in ACP WG- C UAT Subgroup Working Paper UAT-SWG06-WP13. Additional references include ACP WG-C UAT Subgroup Working Paper UAT- SWG06-WP14, Appendix B of the UAT Implementation Manual, and RTCA: UAT-WP

21 Validation of UAT Ground Uplink Message as desired signal A desired signal level of 91 dbm applied at the PMP shall produce a rate of Successful Message Reception of 90% or better under the following conditions: a. When the desired signal is of nominal modulation (i.e., FM deviation is 625 KHz) and at the maximum signal frequency offsets, and subject to relative Doppler shift at ±850 knots. b. When the desired signal is of maximum modulation distortion allowed in Section , at the nominal transmission frequency ±1 PPM, and subject to relative Doppler shift at ±850 knots. Notes: 1. The receiver criteria for Successful Message Reception of UAT Ground Uplink Messages is provided in Section 4 of the Manual on the UAT Detailed Technical Specifications. 2. This requirement ensures the bit rate accuracy supporting demodulation in the UAT equipment is adequate to properly receive the longer UAT Ground Uplink Message. Validation Methods = I B, B UT, IT Measurements of sensitivity on commercially available Garmin GDL 90 UAT Transceivers certified by the United States FAA under TSO C154 is documented in ACP WG-C UAT Subgroup Working Paper UAT-SWG06-WP13 and is confirmed by Integration Testing with a Sensis UAT GBT as described in UAT- SWG09-WP17. Additionally reference ACP WG-C UAT Subgroup Working Paper UAT- SWG06-WP14, and Appendix B of the UAT Implementation Manual Validation of Receiver Selectivity Notes: 1. The undesired signal used is an unmodulated carrier applied at the frequency offset. 2. This requirement establishes the receiver s rejection of the off-channel energy. 21

22 3. It is assumed that ratios in between the specified offsets will fall near the interpolated value. 4. The desired signal used is a UAT ADS-B Long Message at -90 dbm at the PMP, to be received with a 90% Successful Message Reception Rate. 5. The tolerable co-channel continuous wave interference power level for aircraft UAT Receivers is assumed to be -101 dbm or less at the PMP. 6. See Section of the UAT Implementation Manual for a discussion of when a High Performance Receiver is desirable. a. Standard receivers shall meet the selectivity characteristics given in Table 3: Table 3: Standard Receiver Rejection Ratios Frequency Offset from Center Minimum Rejection Ratio (Undesired/Desired level in db) -1.0 MHz MHz 15 (±) 2.0 MHz 50 (±) 10.0 MHz 60 Note: It is assumed that ratios in between the specified offsets will fall near the interpolated value. b. High performance receivers shall meet the more stringent selectivity characteristics given in Table 4 below: Table 4: High Performance Receiver Rejection Ratios Frequency Offset from Center Minimum Rejection Ratio (Undesired/Desired level in db) -1.0 MHz MHz 40 (±) 2.0 MHz 50 (±) 10.0 MHz 60 22

23 Note: See Section of the UAT Implementation Manual for guidance material on the implementation of High Performance Receivers. Validation Methods = I B B The rationale for choosing the Receiver Selectivity for both the Standard Receiver and the High Performance Receiver is detailed in the analysis of Working Papers RTCA: UAT-WP-4-13, UAT-WP-5-08 and UAT-WP The resulting performance of the UAT system in future high density air spaces is presented in Appendix B of the UAT Implementation Manual. The reason for the asymmetry in the selectivity requirement for the High Performance Receiver is to provide extra protection against high-power DME/TACAN transmitters operating at 979 MHz. In general, the frequencies 978 MHz and 979 MHz are reserved for emergency use but are actually used in a very limited way worldwide. A variety of Working Papers generated by RTCA SC-186 WG-5 during the development of the UAT MOPS dealt with this issue. UAT-WP pointed out that these frequencies are used only for ramp testers in the United States. RTCA: UAT-WP-05-15, UAT-WP and UAT-WP pointed out that the frequency 978 MHz is used at a very small number of locations worldwide, while 979 MHz is used much more often. So, while it may be possible to vacate the users at 978 MHz, the users at 979 MHz are expected to remain (and more such users may be put in place). Since there are currently no users at 977 MHz, it was determined that certain receivers needed more protection from interferers at +1 MHz than at -1 MHz. Because the interference is asymmetrical, it was decided that the selectivity requirement could also be made asymmetrical. (Note that, although the requirement is asymmetrical, there is no prohibition against building a receiver with symmetrical selectivity provided the minimum requirements are met.) Because the High Performance receivers are expected to operate at the highest altitudes and thus experience the most interference and because they have the most stringent performance requirements (update rate versus range), they need the most interference protection. Working Paper RTCA: UAT-WP-7-10 reported on simulation results indicating that the performance of high-flying aircraft receivers (A3) would be markedly improved with the narrower, asymmetrical receiver filters available to be tested at the time. The more relaxed specifications for the Standard Receivers selectivity were shown to be sufficient for them to meet their requirements. 23

24 Validation of Receiver Desired Signal Dynamic Range The receiver shall achieve a Successful Message Reception rate for Long ADS-B Messages of 99% or better when the desired signal level is between 90 dbm and 10 dbm at the PMP in the absence of any interfering signals. Note: The value of 10 dbm represents 120-foot separation from an aircraft transmitter transmitting at maximum allowed power. Validation Method = I A, MD The Receiver Desired Signal Dynamic Range of 99% for UAT was initially set as the standard based on this figure being accepted as requirements for dynamic range for Transponders and the 1090 MHz Extended Squitter ADS-B data link. The figure of 99% can be found in ICAO SARPs and RTCA MOPS documents as a reference for its inclusion into the first draft of the UAT MOPS, documented in Working Paper RTCA: UAT-WP ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP06 summarizes the test results from Garmin Aviation Technologies certification testing on their GDL 90 UAT Transceiver, certified to FAA TSO-C154. ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP16 summarizes the test results from the FAATC of several sets of UAT equipment, including: (1) a Ground Based Transceiver (GBT) which is now a commercially available product of the Sensis Corporation, (2) a commercially available UAT Transceiver, certified by the United States FAA under TSO-C154 as Class A1H avionics equipment, and marketed under the model number GDL-90 by Garmin International, (3) a UAT Receiver which was specifically modified to have the same filter characteristics as a Class A3, High Performance UAT Receiver, specifically for UAT SARPs validation activities, and (4) a prototype Class A3, High Performance Transmitter produced by Rockwell Collins Corporation specifically for UAT SARPs validation testing. The modified Class A3 Receiver (#3 above) did not meet the UAT SARPs Dynamic Range requirement. It did not achieve 99% Message Success Rate at the required -90 dbm. Testing showed that it achieved 99% SMR at approximately -89 dbm. The UAT Subgroup reviewed the results specified in UAT-SWG08-WP16 and agreed that a production Class A3 UAT Receiver meeting this requirement can be produced, particularly given the satisfaction of this requirement by the Garmin GDL-90 Class A1H (#2 above) certified UAT Receiver, and that the UAT SARPs requirement should be considered validated. 24

25 Validation of Receiver Tolerance to Pulsed Interference Note: All power level requirements in this section are referenced to the PMP. a. For Standard and High Performance receivers the following requirements shall apply: 1. The receiver shall be capable of achieving 99% SMR of Long UAT ADS-B Messages when the desired signal level is between 90 dbm and 10 dbm when subjected to DME interference under the following conditions: DME pulse pairs at a nominal rate of 3,600 pulse pairs per second at either 12 or 30 microseconds pulse spacing at a level of 36 dbm for any 1 MHz DME channel frequency between 980 MHz and 1213 MHz inclusive. 2. Following a 21 microsecond pulse at a level of ZERO (0) dbm and at a frequency of 1090 MHz, the receiver shall return to within 3 db of the specified sensitivity level (see ) within 12 microseconds. b. For the Standard Receiver the following additional requirements shall apply: 1. The receiver shall be capable of achieving 90% SMR of Long UAT ADS-B Messages when the desired signal level is between 87 dbm and 10 dbm when subjected to DME interference under the following conditions: DME pulse pairs at a nominal rate of 3,600 pulse pairs per second at a 12 microseconds pulse spacing at a level of 56 dbm and a frequency of 979 MHz. 2. The receiver shall be capable of achieving 90% SMR of Long UAT ADS-B Messages when the desired signal level is between 87 dbm and 10 dbm when subjected to DME interference under the following conditions: DME pulse pairs at a nominal rate of 3,600 pulse pairs per second at a 12 microseconds pulse spacing at a level of 70 dbm and a frequency of 978 MHz. c. For the High Performance Receiver the following additional requirements shall apply: 1. The receiver shall be capable of achieving 90% SMR of Long UAT ADS-B Messages when the desired signal level is between 87 dbm and 10 dbm when subjected to DME interference under the following conditions: DME pulse pairs at a nominal rate of 3,600 pulse pairs per second at a 12 microseconds pulse spacing at a level of 43 dbm and a frequency of 979 MHz. 2. The receiver shall be capable of achieving 90% SMR of Long UAT ADS-B Messages when the desired signal level is between 87 dbm and 10 dbm when subjected to DME interference under the following conditions: DME pulse pairs at a nominal rate of 3,600 pulse pairs per second at a 12 microseconds pulse spacing at a level of 79 dbm and a frequency of 978 MHz. 25

26 Validation Methods = I B, B UT Working Paper RTCA: UAT-WP and its supporting data show that Pre-MOPS UAT transceivers met all pulsed interference requirements, based upon testing conducted at the United States Joint Spectrum Center. ACP WG-C UAT Subgroup Working Paper UAT-SWG09-WP23 summarizes pulsed interference testing conducted by Garmin International as part of the certification process of Garmin s GDL 90 Class A1H UAT Transceiver. This Working Paper reports that the GDL 90 met all pulsed interference test requirements. ACP WG-C UAT Subgroup Working Paper UAT-SWG09-WP22, as revised during the meeting #9 of the UAT Subgroup, summarizes further testing performed by the FAATC on certified UAT Avionics and reports a discrepancy in results between that testing and testing reported in Working Papers discussed above. Specifically, while this Working Paper shows compliance with the requirements at 978 MHz and 979 MHz, the Working Paper also contains results at a 6 db variance to those in the other two Working Papers described above for the 980 MHz tests ( subparagraph 1.a). The Working Paper contains a detailed discussion of this discrepancy and provides rationale for a change made at the UAT Subgroup Meeting #9 in the pulsed interference requirement at 980 MHz to 1215 MHz. This change was to specify the signal strength of the pulsed interference at the PMP to be 36 dbm instead of 30 dbm. The UAT Subgroup agreed that the revised requirement had been validated by all tests conducted VALIDATION OF PHYSICAL LAYER CHARACTERISTICS Validation of Modulation Rate The modulation rate shall be Mbps with a tolerance for aircraft transmitters of ±20 PPM, and a tolerance for ground transmitters of ±2 PPM. Note: The tolerance on the modulation rate is consistent with the requirement on modulation distortion (See ). 26

27 Validation Methods = I BB The rationale for choosing the frequency stability at ±20 PPM was originally demonstrated in RTCA: UAT-WP-4-11A. The choice was made for the following reason: The proposed UAT uplink format consists of 6 blocks of RS(92,72), preceded with a single 36-bit synchronization pattern. The single-sync pattern requirement has an impact on the data rate tolerance. Allowing for 1/10 of a bit clock drift over the duration of the message: 6 * 92 * 8 = 4416 bits per uplink, divided into 1/10 of a bit, or ±24 PPM for the link. In order to avoid requiring an expensive reference oscillator in the avionics, the accuracy of the avionics was limited to ±20 PPM. ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP15 summarizes DFS testing on a High Performance Class Transmitter. ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP06 summarizes the test results from Garmin Aviation Technologies certification testing on their GDL 90 UAT Transceiver, certified to FAA TSO-C Validation of Modulation Type a. Data shall be modulated onto the carrier using binary Continuous Phase Frequency Shift Keying. The modulation index, h, shall be no less than 0.6; b. A binary ONE (1) shall be indicated by a shift up in frequency from the nominal carrier frequency and a binary ZERO (0) by a shift down from the nominal carrier frequency. Notes: 1. Filtering of the transmitted signal (at base band and/or after frequency modulation) will be required to meet the spectral containment requirement of Section This filtering may cause the deviation to exceed these values at points other than the optimum sampling points. 27

28 2. Because of the filtering of the transmitted signal, the received frequency offset varies continuously between the nominal values of ±312.5 khz (and beyond), and the optimal sampling point may not be easily identified. This point can be defined in terms of the so-called eye diagram of the received signal. The ideal eye diagram is a superposition of samples of the (undistorted) post detection waveform shifted by multiples of the bit period (0.96 microseconds). The optimum sampling point is the point during the bit period at which the opening of the eye diagram (i.e., the minimum separation between positive and negative frequency offsets at very high signal-to-noise ratios) is maximized. An example eye diagram can be seen in Figure 3. The timing of the points where the lines converge defines the optimum sampling point. Figure 4 shows an eye pattern that has been partially closed by modulation distortion. Well defined optimum sampling point. Figure 3: Ideal eye diagram Poorly defined optimum sampling point. Figure 4: Distorted eye diagram 28

29 Validation Method = I BB Reference Mitre Technical Report MTR96W28R1, posted as Working Paper RTCA: UAT-WP Additional reference ICAO ACP WG-C UAT Subgroup Working Paper UAT-SWG08-WP15 summarizes DFS testing on a High Performance Class UAT Transmitter Validation of Modulation Distortion a. For aircraft transmitters, the minimum vertical opening of the eye diagram of the transmitted signal (measured at the optimum sampling points) shall be no less than 560 khz when measured over an entire Long UAT ADS-B Message containing pseudorandom Message Data Blocks. b. For ground transmitters, the minimum vertical opening of the eye diagram of the transmitted signal (measured at the optimum sampling points) shall be no less than 560 khz when measured over an entire UAT Ground Uplink Message containing pseudorandom Message Data Blocks. c. For Aircraft transmitters, the minimum horizontal opening of the eye diagram of the transmitted signal (measured at 978 MHz) shall be no less than µs (0.65 symbol periods) when measured over an entire Long UAT ADS-B Message containing pseudorandom Message Data Blocks. d. For ground transmitters, the minimum horizontal opening of the eye diagram of the transmitted signal (measured at 978 MHz) shall be no less than µs (0.65 symbol periods) when measured over an entire UAT Ground Uplink Message containing pseudorandom Message Data Blocks. Notes: 1. Section defines the UAT ADS-B Message types. 2. The ideal eye diagram is a superposition of samples of the (undistorted) post detection waveform shifted by multiples of the bit period (0.96 microseconds). Validation Methods = I B, B A, UT Working Papers RTCA: UAT-WP-9-02 and UAT-WP ACP WG-C UAT Subgroup Working Papers UAT-SWG06-WP12 and UAT-SWG07-WP04 29