Garmin AT, Inc. GDL 90 UAT Data Link Sensor Technical Report Document Revision: -- 16 January 2005 16-Jan-2005 Page 1 of 41
Rev Date Description -- 16-Jan-2005 Initial Release. MS Word 2002. Revision Log Title: Garmin AT, Inc. GDL 90 UAT Data Link Sensor Technical Report Cage Code 0XCJ6 2345 Turner Rd. S. E. Salem, Oregon USA Prepared By: T. Mosher, Senior Design Engineer Date: 16-Jan-2005 16-Jan-2005 Page 2 of 41
Table of Contents 1. INTRODUCTION...6 1.1. Purpose... 6 1.2. Scope... 6 1.3. References... 6 1.3.1. Garmin AT, Inc...6 1.3.2. U.S. Federal Aviation Administration...6 1.3.3. Industry Standards...6 1.4. Test Equipment... 6 1.5. Test Setup... 7 2. REQUIREMENTS VALIDATION...8 2.1. Transmitter Output Power... 8 2.1.1. Requirement Text...8 2.1.2. Validation Procedure...9 2.1.3. Measurements & Figures...11 2.1.4. Conclusion...13 2.2. Receiver Desired Signal Dynamic Range... 14 2.2.1. Requirement Text...14 2.2.2. Validation Procedure...14 2.2.3. Measurements & Figures...14 2.2.4. Conclusion...15 2.3. Modulation Rate... 16 2.3.1. Requirement Text...16 2.3.2. Validation Procedure...16 2.3.3. Measurements & Figures...16 2.3.4. Conclusion...16 2.4. Modulation Distortion... 17 2.4.1. Requirement Text...17 2.4.2. Validation Procedure...17 2.4.3. Measurements & Figures...17 2.4.4. Conclusion...19 2.5. UTC Coupled Condition... 20 2.5.1. Requirement Text...20 2.5.2. Validation Procedure...20 2.5.3. Measurements & Figures...20 2.5.4. Conclusion...20 2.6. Non-UTC Coupled Condition... 21 2.6.1. Requirement Text...21 2.6.2. Validation Procedure...21 2.6.3. Measurements & Figures...22 2.6.4. Conclusion...22 2.7. Message Start Opportunity (MSO)... 23 2.7.1. Requirement Text...23 16-Jan-2005 Page 3 of 41
2.7.2. Validation Procedure...23 2.7.3. Measurements & Figures...24 2.7.4. Conclusion...25 2.8. Relationship of the MSO to the Modulated Data... 26 2.8.1. Requirement Text...26 2.8.2. Validation Procedure...26 2.8.3. Measurements & Figures...26 2.8.4. Conclusion...27 2.9. Time Registration and Latency... 28 2.9.1. Requirement Text...28 2.9.2. Validation Procedure...28 2.9.3. Conclusion...28 2.10. Non-Precision Condition and UTC Coupled... 29 2.10.1. Requirement Text...29 2.10.2. Validation Procedure...29 2.10.3. Measurements & Figures...30 2.10.4. Conclusion...31 2.11. Precision Condition and UTC Coupled... 32 2.11.1. Requirement Text...32 2.11.2. Validation Procedure...32 2.11.3. Measurements & Figures...32 2.11.4. Conclusion...33 2.12. Requirements when Non-UTC Coupled... 34 2.12.1. Requirement Text...34 2.12.2. Validation Procedure...34 2.12.3. Conclusion...34 2.13. Data Timeout... 35 2.13.1. Requirement Text...35 2.13.2. Validation Procedure...35 2.13.3. Conclusion...35 2.14. Turnaround Time... 37 2.14.1. Requirement Text...37 2.14.2. Validation Procedure...37 2.14.3. Measurements & Figures...37 2.14.4. Conclusion...37 2.15. Receiver Time of Message Receipt... 38 2.15.1. Requirement Text...38 2.15.2. Validation Procedure...38 2.15.3. Measurements & Figures...38 2.15.4. Conclusion...39 2.16. Report Assembly on Receipt of Messages... 40 2.16.1. Requirement Text...40 2.16.2. Validation Procedure...40 2.16.3. Measurements & Figures...40 2.16.4. Conclusion...40 16-Jan-2005 Page 4 of 41
2.17. Message Reception-to-Report Completion Time... 41 2.17.1. Requirement Text...41 2.17.2. Validation Procedure...41 2.17.3. Measurements & Figures...41 2.17.4. Conclusion...41 Table of Figures FIGURE 1 - GDL 90 TEST EQUIPMENT RACK AND VIBRATION TEST FIXTURE...7 FIGURE 2 - TEST SETUP A...9 FIGURE 3 - TEST SETUP E...10 FIGURE 4 - TX OFF TO ACTIVE STATE...11 FIGURE 5 - TX ACTIVE TO OFF STATE...12 FIGURE 6 - LEADING EDGE OF POWER INACTIVE STATE...12 FIGURE 7 -TRAILING EDGE OF POWER INACTIVE STATE...13 FIGURE 8 - RECEIVER DYNAMIC RANGE...15 FIGURE 9 - EYE DIAGRAM, VERTICAL OPENING...18 FIGURE 10 - EYE DIAGRAM, HORIZONTAL OPENING...18 FIGURE 11 - MODULATED DATA TIMING...27 FIGURE 12 - REPORTED POSITION, NON-PRECISION CONDITION...30 FIGURE 13 - POSITION ERROR, NON-PRECISION CONDITION...30 FIGURE 14 - TOMR ACCURACY...39 16-Jan-2005 Page 5 of 41
1. Introduction 1.1. PURPOSE This document demonstrates how the GDL 90 UAT Data Link Sensor complies with certain requirements of the draft UAT SARPs and UAT Technical Manual. 1.2. SCOPE The requirements validated in this report were requested by the UAT SARPs subgroup of Working Group C of the ICAO Aeronautical Communication Panel. Where appropriate, use is made of data originally collected to show compliance with FAA TSO-C154. 1.3. REFERENCES 1.3.1. Garmin AT, Inc. PD3612 Rev C GDL 90 Functional Performance Test Plan and Report 1.3.2. U.S. Federal Aviation Administration TSO-C154 1.3.3. Industry Standards RTCA/DO-282A UAT MOPS 1.4. TEST EQUIPMENT The following specialized test equipment was used in performance of these tests. RF signal generator, Rhode & Schwarz SMIQ 03 Vector Signal Analyzer, Agilent/HP 89441A GPS/GNSS simulator, NavLabs LP In addition, a UAT Test Set was constructed to provide signals for certain RF test scenarios as required. 16-Jan-2005 Page 6 of 41
1.5. TEST SETUP The following figures illustrate typical test setups, for illustration. Figure 1 - GDL 90 Test Equipment Rack and Vibration Test fixture 16-Jan-2005 Page 7 of 41
2. Requirements Validation This section provides validation of each applicable SARPs requirement. For each requirement, the source is identified and reference is made to any equivalent RTCA/DO-282A validation procedure. The validation procedure is given, and any appropriate measurements and figures are presented. 2.1. TRANSMITTER OUTPUT POWER Source: draft UAT SARPs 12.1.2.6 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.2.5 2.1.1. Requirement Text 12.1.2.6 Transmitter Power Output Requirements 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 ( 12.4.4.1.1, 12.4.4.2.1) appearing at the output port of the equipment. a. Prior to 8 bit periods before the reference time, the average RF output power (300 KHz measurement bandwidth) shall not exceed 80 dbm. b. Between 8 and 6 bit periods prior to the reference time, the RF output power (2 MHz measurement bandwidth) shall remain at least 20 db below the minimum power requirement for the UAT equipment class. c. During the Active state, defined as beginning at the reference time and continuing for the duration of the message the RF output power (2 MHz measurement bandwidth) shall be greater than or equal to the minimum power requirement for the UAT equipment class. d. The RF output power (2 MHz measurement bandwidth) 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 (2 MHz measurement bandwidth) 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 average RF output power (300 KHz measurement bandwidth) shall fall to a level not to exceed 80 dbm. 16-Jan-2005 Page 8 of 41
Reference figure (from SARPs Figure 2) 2.1.2. Validation Procedure Test Date: 01 May 2004 Equipment Setup: Use Setup A or Setup E as required. Figure 2 - Test Setup A 16-Jan-2005 Page 9 of 41
Figure 3 - Test Setup E All of the output power measurements are adjusted for 3dB loss allocated for cabling to the antenna of the aircraft. On each test below set up the UAT equipment to transmit a Long ADS-B Message. In this test, the data has been adjusted by 3 db. Step 1: Measure Active State RF Power Output Using setup A, verify that the minimum and maximum power values specified for the equipment class are satisfied over the entire message. Step 2: Verify RF Transmitter Power Prior to the Active State Using setup A, verify that the power measurement does not exceed the corresponding allowable power level for the equipment class. Step 3: Verify RF Transmitter Power Post Active State Using setup A, verify that the power measurement does not exceed the corresponding allowable power level for the equipment class. Step 4: Measure Inactive State RF Power Output Using setup E, verify that the power measurement does not exceed the corresponding allowable power level for the equipment class. The MOPS requirement is beyond the capability of the VSA. An external antenna switch in conjunction with a 40 db LNA (low noise amplifier) is required to make the measurement. Aggressive time averaging must be used on the VSA in order to observe the required -80 dbm noise floor. Step 5: Measure Power at the Non-Selected Antenna Port Use setup A. Select the top antenna port. Verify that the power measured at the Bottom antenna port is 20 db or more below the power measured on the Top antenna port. Repeat the test on the Bottom antenna port. 16-Jan-2005 Page 10 of 41
2.1.3. Measurements & Figures Parameter Criteria Measurement Result Active State Power Min: +42 dbm +45.0 dbm Pass Max: +46 dbm Droop: +/- 2 db 0.3 db Pass Prior to Active State < +22 dbm ~0 dbm (see Figure 4) Pass Post Active State < +22 dbm ~0 dbm (see Figure 5) Pass Non-selected antenna port > 20 db isolation Top: 24 db isolation Pass Bottom: 30 db isolation Pass Inactive State Power < -80 dbm -82 dbm (see Figure 6 and Figure 7) Pass Note: all Vector Signal Analyzer signal levels are reduced by a 30.0 db fixed RF attenuator, plus compensation for 3 db of installation losses. Figure 4 - Tx Off to Active State In the figure above, the first bit start time is at the cursor. Bit times are approximately one major unit horizontally. 16-Jan-2005 Page 11 of 41
Figure 5 - Tx Active to Off State In the figure above, the last bit end time is at the cursor. Bit times are approximately one major unit horizontally. Figure 6 - Leading edge of Power Inactive State 16-Jan-2005 Page 12 of 41
In the figure above, the cursor is set 8 bits prior to active state, and measures -85 dbm after compensation for the 40 db gain of the LNA. Figure 7 -Trailing edge of Power Inactive State In the figure above, the cursor is set 8 bits after the last bit of the message, and measures -95 dbm after compensation for the 40 db gain of the LNA. 2.1.4. Conclusion The GDL 90 meets all requirements for Transmitter Output Power. 16-Jan-2005 Page 13 of 41
2.2. RECEIVER DESIRED SIGNAL DYNAMIC RANGE Source: draft UAT SARPs 12.3.2.3 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.8.2.2 2.2.1. Requirement Text 12.3.2.3 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 antenna in the absence of any interfering signals. 2.2.2. Validation Procedure Test Date: 18 February 2004 Using test setup A (see Figure 2), provide the GDL 90 under test with Long ADS-B messages having pseudo-random payload data and valid FEC parity symbols and the following characteristics: 978.000 MHz center frequency 625 KHz FM deviation (measured at the optimum sampling point) RF signal level variable from -90 dbm to -10 dbm, referenced at the antenna port (allowing for 3 db installation losses) Apply messages to unit under test Top antenna port. Measure receiver MSR (Message Success Rate), out of 1,000 messages. Modify RF signal level and repeat Step 2 to cover -90 dbm to -10 dbm in 10 db steps. Repeat for Bottom antenna port. 2.2.3. Measurements & Figures Parameter Criteria Measurement (MSR) Result MSR at -90 dbm >= 99% Top: 0.999 Bottom: 0.999 Pass MSR at -80 dbm >= 99% Top: 0.999 Bottom: 0.999 Pass MSR at -70 dbm >= 99% Top: 1.000 Bottom: 0.999 Pass MSR at -60 dbm >= 99% Top: 0.999 Bottom: 0.999 Pass MSR at -50 dbm >= 99% Top: 0.999 Bottom: 0.999 Pass MSR at -40 dbm >= 99% Top: 1.000 Bottom: 0.999 Pass MSR at -30 dbm >= 99% Top: 0.999 Bottom: 0.999 Pass MSR at -20 dbm >= 99% Top: 1.000 Bottom: 0.999 Pass MSR at -10 dbm >= 99% Top: 1.000 Bottom: 0.999 Pass Note: Top and Bottom antenna ports have identical performance to within the measurement error (1 message out of 1,000). 16-Jan-2005 Page 14 of 41
Message Success Rate (Long ADS-B) MSR Limit 1.2 1 0.8 MSR 0.6 0.4 0.2 0-110 -100-90 -80-70 -60-50 -40-30 -20-10 0 RF level at antenna (dbm) Figure 8 - Receiver Dynamic Range 2.2.4. Conclusion The GDL 90 meets requirements for Receiver Desired Signal Dynamic Range. 16-Jan-2005 Page 15 of 41
2.3. MODULATION RATE Source: draft UAT SARPs 12.4.1 RTCA/DO-282A, UAT MOPS, Equivalent: none 2.3.1. Requirement Text 12.4.1 Modulation Rate The modulation rate shall be 1.041667 Mbps with a tolerance for airborne transmitters of +/-20 ppm. 2.3.2. Validation Procedure Test Date: December 2004 There is no direct measurement method available that will measure the modulation rate for ADS-B transmissions with sufficient accuracy to validate this requirement. Alternate means of validation must be used. Note that RTCA/DO-282A relies on the Modulation Distortion measurement of the transmitted eye pattern, to verify that the transmitted symbol drift rate over the duration of an ADS-B transmission is sufficiently small such that the transmitted data can be successfully recovered. The design for the Garmin GDL 90 equipment uses a digitally-controlled message transmission process. The transmitted modulation rate is derived from an internal Reference Clock, and therefore the Modulation Rate has the same accuracy as the Reference Clock. Bench measurements were made of the Reference Clock accuracy in the worst-case condition (i.e. unit operating with no GNSS fix). Results are given below. 2.3.3. Measurements & Figures Parameter Criteria Measurement Result Reference Clock Frequency < +/- 20 PPM < +/- 1.5 PPM Pass 2.3.4. Conclusion The GDL 90 meets requirements for Modulation Rate. 16-Jan-2005 Page 16 of 41
2.4. MODULATION DISTORTION Source: draft UAT SARPs 12.4.3 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.2.4 2.4.1. Requirement Text 2.4.2. Validation Procedure 12.4.3 Modulation Distortion (subparagraphs a and c only) a. For airborne 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 payload data. b. (omitted - applies to base stations only). c. The minimum horizontal opening of the eye diagram of the transmitted signal (measured at 978 MHz) shall be no less than 0.624 µs (0.65 symbol periods) when measured over an entire Long ADS-B Message containing pseudorandom payload data. Test Date: 17 February 2004 Use Test Setup A. Configure the VSA (Vector Signal Analyzer) to demodulate UAT messages and display the received eye diagram. Configure the GDL 90 unit under test to transmit ADS-B messages containing pseudo-random payload data. Connect the unit under test to the VSA with RF attenuation as necessary. Connect the External Trigger input of the VSA to the Transmitter timing test point on the GDL 90 unit under test. To measure the Vertical Eye Diagram opening, temporarily set the VSA Data Format to part real(i). Visually scan the demodulated data display to find the 1 bit that has the lowest amplitude, and the 0 bit that has the highest amplitude. Without moving the markers, set the VSA Data Format to eye diagram I. The cursors will be shown on the eye diagram display at the point of minimum vertical opening of the eye diagram. Record the cursor delta value in kilohertz. To measure the Horizontal Eye Diagram opening, manually scroll the cursor markers through the captured data buffer, until the zero-crossing points are found that yield the minimum horizontal eye diagram opening. The minimum horizontal opening is the fractional portion of the marker delta, in fractions of a symbol. 2.4.3. Measurements & Figures Parameter Criteria Measurement Result Vertical Eye Diagram Opening > 560 KHz 581.5 KHz Pass Horizontal Eye Diagram Opening > 0.65 bit periods 0.80 bit periods Pass 16-Jan-2005 Page 17 of 41
Figure 9 - Eye Diagram, vertical opening Figure 10 - Eye Diagram, horizontal opening The marker positions were adjusted to select the minimum horizontal eye pattern opening. The net opening of the horizontal eye diagram is the fractional portion of marker delta (0.80 bit periods). 16-Jan-2005 Page 18 of 41
2.4.4. Conclusion The GDL 90 meets requirements for Modulation Distortion. 16-Jan-2005 Page 19 of 41
2.5. UTC COUPLED CONDITION Source: draft Technical Manual 3.1.1.1 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.5.1 2.5.1. Requirement Text 3.1.1.1 UTC Coupled Condition The UTC Coupled subfield shall be set to ONE, except under the conditions discussed in 3.1.1.2. The conditions discussed in 3.1.1.2 for the non-utc coupled condition are: 1 - when no external time mark is supplied (subparagraph a) 2 - within 2 seconds of loss of UTC reference (subparagraph b), and 3 - for at most 2 seconds after acquisition of UTC reference (subparagraph f) 2.5.2. Validation Procedure Test Date: 8 March 2004 The GDL 90 does not support use of an external time mark, so condition 1 cannot be validated. To validate conditions 2 and 3, provide the GDL 90 equipment with a GNSS signal source. Use a terminal emulator connected to the Maintenance port to display the status of the internal GNSS receiver and the transmitted payload data. 2.5.3. Measurements & Figures Parameter Criteria Measurement Result Time from loss of UTC reference < 2 seconds 1 second Pass to reporting of UTC Coupled field being set to ZERO. Time from acquisition of UTC reference to reporting of UTC Coupled field being set to ONE. < 2 seconds 1 second Pass 2.5.4. Conclusion The GDL 90 meets requirements for the UTC Coupled Condition. 16-Jan-2005 Page 20 of 41
2.6. NON-UTC COUPLED CONDITION Source: draft Technical Manual 3.1.1.2 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.5.2 2.6.1. Requirement Text 3.1.1.2 Non-UTC Coupled Condition a. This condition shall be entered when the ADS-B equipment has not been provided a GPS/GNSS, or equivalent, time mark. b. Within 2 seconds of entering the Non-UTC Coupled condition, the UAT equipment shall set the UTC Coupled subfield to ZERO in any transmitted messages. c. While in the non-utc Coupled Condition, Airborne UAT equipment with operational receivers shall be capable of aligning to within +/- 6 milliseconds of UTC time based upon successful message reception of any UAT Ground Uplink Message with the UTC Coupled bit set. d. While in the non-utc Coupled Condition when UAT Ground Uplink Messages cannot be received, the UAT transmitter shall estimate or coast time through the outage period such that the drift rate of estimated time, relative to actual UTC-coupled time, is no greater than 12 milliseconds in 20 minutes. e. While in the non-utc Coupled Condition, ADS-B transmissions shall continue. f. The UAT equipment shall change state to the UTC coupled condition within 2 seconds of availability of the UTC coupled source. 2.6.2. Validation Procedure Test Date: 8 March 2004 The requirement of subparagraph a does not apply to the GDL 90, since it does not support an external time mark signal. The requirements of subparagraphs b and f were validated in 2.5 of this report. Validation of Subparagraph c : Using Test Setup A, configure the UAT Test Set to generate simulated Uplink messages. Provide a GNSS signal to the UAT Test Set. Disconnect any GNSS source from the GDL 90 unit under test. Connect an oscilloscope to the time reference test points on the UAT Test Set (on Channel 1) and the unit under test (on Channel 2). Measure the time difference between the time mark signals on Channel 1 and Channel 2. The time difference is a direct measurement of the ability to synchronize the GDL 90 time reference to reception of an Uplink message. Record the measurement. Validation of Subparagraph d : Discontinue the transmission of Uplink messages by the UAT Test Set. After 20 minutes, measure the time difference between the time mark signals on Channel 1 and Channel 2. The time difference is a direct measurement of the ability of the GDL 90 to maintain its timing 16-Jan-2005 Page 21 of 41
reference in the absence of either GNSS signals or reception of Uplink messages. Record the measurement. For Subparagraph e, observe that payloads continue to be transmitted during periods of no GNSS fix (and therefore without UTC coupling), and that the UTC Coupled subfield is set to the ZERO value. 2.6.3. Measurements & Figures Parameter Criteria Measurement Result Subparagraph c: Time alignment on receipt of < +/- 6 msec +0.23 msec Pass Uplink message Subparagraph d: Coast time w/o Uplink message < 12 msec in 20 +0.84 msec Pass minutes Continued transmission without UTC coupling Required Observed Pass 2.6.4. Conclusion The GDL 90 meets the requirements for the Non-UTC Coupled condition. 16-Jan-2005 Page 22 of 41
2.7. MESSAGE START OPPORTUNITY (MSO) Source: draft Technical Manual 3.1.2.1 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.6.2.1 2.7.1. Requirement Text 3.1.2.1 The Message Start Opportunity (MSO) UAT ADS-B Messages shall be transmitted at discrete Message Start Opportunities (MSO) chosen by the following pseudo-random process. See the Technical Manual for the full text of the procedure MSO selection algorithm. 2.7.2. Validation Procedure Test Date: 28 February 2004 Validation of full MSO range selection: Use a GNSS simulator to provide a position to the unit under test in UAT angular units of exactly 0x08A868 Latitude (12.175083 degrees N) and 0x05A23A Longitude (7.9223861 degrees E). Place the unit under test into the Airborne mode using the Air/Ground input discrete signal. Verify that the sequence of MSO selected for the first thirty-one ADS-B message transmissions is as shown in the following table. t (sec) MSO t (sec) MSO 0 2904 16 2280 1 3474 17 2850 2 826 18 3402 3 2996 19 2372 4 1948 20 1324 5 2518 21 1894 6 3070 22 2446 7 2040 23 1416 8 992 24 3568 9 1562 25 938 10 2114 26 1490 11 1084 27 3660 12 3236 28 2612 13 3806 29 3182 14 1158 30 3734 15 3328 -- -- Definition: The MSO values for each of the restricted MSO ranges are as follows: 1 st restricted range: MSOs 752 to 1551 2 nd restricted range: MSOs 1552 to 2351 16-Jan-2005 Page 23 of 41
3 rd restricted range: MSOs 2352 to 3151 4 th restricted range: MSOs 3152 to 3951 Validation of restricted range selection: Continue from the previous step. Set the Air/Ground discrete input on the unit under test to indicate On- Ground. Verify that the range of MSOs selected lies within one of the restricted ranges. Note: Exactly which range is selected depends on the exact timing of entering the Onground condition, and is not the subject of this test. This step validates that the unit under test transitions from the using the full airborne MSO range to using a restricted range upon entering the On-ground condition. Validation of use of each restricted range: Set the Air/Ground input discrete to Airborne. Set the Latitude and Longitude to the value in UAT angular units of 0x000321. Set the Air/Ground input to On-ground. Verify that the range of MSOs selected is from the 2 nd restricted range. Set the Air/Ground input discrete to Airborne. Set the Latitude and Longitude to the value in UAT angular units of 0x000641. Set the Air/Ground input to On-ground. Verify that the range of MSOs selected is from the 3 rd restricted range. Set the Air/Ground input discrete to Airborne. Set the Latitude and Longitude to the value in UAT angular units of 0x000961. Set the Air/Ground input to On-ground. Verify that the range of MSOs selected is from the 4 th restricted range. Set the Air/Ground input discrete to Airborne. Set the Latitude and Longitude to the value in UAT angular units of 0x000C81. Set the Air/Ground input to On-ground. Verify that the range of MSOs selected is from the 1 st restricted range. 2.7.3. Measurements & Figures Parameter Criteria Measurement Result MSO Selection, full Airborne range per table All MSO selections are correct Pass Transition to restricted range use any restricted range Confirmed Pass when becoming On-ground Use of 2 nd restricted range 2 nd range only Confirmed Pass Use of 3 rd restricted range 3 rd range only Confirmed Pass Use of 4 th restricted range 4 th range only Confirmed Pass Use of 1 st restricted range 1 st range only Confirmed Pass 16-Jan-2005 Page 24 of 41
2.7.4. Conclusion The GDL 90 complies with the requirements for the Message Start Opportunity. 16-Jan-2005 Page 25 of 41
2.8. RELATIONSHIP OF THE MSO TO THE MODULATED DATA Source: draft Technical Manual 3.1.2.2 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.6.2.2 2.8.1. Requirement Text 3.1.2.2 Validation of Relationship of the MSO to the Modulated Data The optimum sample point of the first bit of the UAT synchronization sequence at the antenna terminal of the UAT equipment shall occur at TTX microseconds after the 1 second UTC epoch according to the following formula: TTX (microseconds) = 6000 + (250*MSO) within the following tolerances: a. +/- 500 nanoseconds for UAT equipment with an internal UTC coupled time source, b. +/- 500 nanoseconds for UAT equipment with an external UTC coupled time source. 2.8.2. Validation Procedure Test Date: 31 March 2004 Using Test Setup A, provide a live GNSS signal to the GDL 90 unit under test. Connect a 1 pulse per second timing reference signal to the External Trigger input of the VSA (Vector Signal Analyzer). Configure the unit under test to transmit only in MSO 3950. Configure the VSA to demodulate UAT messages, with the following parameters: External Trigger with a time delay of 993.5 msec. Time span: 25 symbols Display format: Real part (I) Note that an ADS-B message transmitted in MSO 3950 should have the first bit of the synchronization pattern occur at 993.5 milliseconds after the 1 PPS timing reference. Since the first few modulated bits of the ADS-B Sync pattern are the pattern 11101, the peak value of the 0 bit in this sequence (in the 4 th bit position) provides a well defined event that can be identified and measured with the VSA cursor markers. Place a marker on the peak value of the 4 th bit position. The time delay (in symbols) to this point should be 3 symbol periods after the optimum sample point of the first bit of the synchronization sequence. The GDL 90 does not support use of external UTC coupled time sources, so Subparagraph b of the requirement cannot be validated. 2.8.3. Measurements & Figures Parameter Criteria Measurement Result Position of first 0 bit in 3.0 +/- 0.5 symbols 3.0 symbols Pass synchronization sequence 16-Jan-2005 Page 26 of 41
Figure 11 - Modulated Data Timing The marker position shows that the 4 th bit of the synchronization pattern occurs 3.0 symbols after the triggering event. 2.8.4. Conclusion The GDL 90 meets the requirements for the Relationship of the MSO to the Modulated Data 16-Jan-2005 Page 27 of 41
2.9. TIME REGISTRATION AND LATENCY Source: draft Technical Manual 3.1.3 RTCA/DO-282A, UAT MOPS, Equivalent: none Note: MOPS 2.4.7.2 contains similar text to Technical Manual 3.1.3, but the MOPS text contains no testable requirements. 2.9.1. Requirement Text 3.1.3 Time Registration and Latency The UAT transmitter shall use the Precision or Non-Precision condition for reporting SV data according to the criteria below: a. Precision condition shall be in effect when: 1. The NACP value is 10 or 11, or 2. The NIC value is 9, 10 or 11 b. Otherwise, the Non-Precision condition shall be in effect. 2.9.2. Validation Procedure Test Date: n/a This requirement is validated by compliance with the separate requirements for Precision and Non- Precision timing modes. See 2.10 and 2.11 of this document. 2.9.3. Conclusion The GDL 90 meets the requirements for Time Registration and Latency. 16-Jan-2005 Page 28 of 41
2.10. NON-PRECISION CONDITION AND UTC COUPLED Source: draft Technical Manual 3.1.3.1 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.7.2.1 2.10.1. Requirement Text 3.1.3.1 Requirements When in Non-Precision Condition and UTC Coupled When the UAT Transmitting Subsystem is in the Non-Precision Condition, and is UTC Coupled: a. At the time of the ADS-B Message transmission, position information that is encoded in the LATITUDE and LONGITUDE fields, and in the ALTITUDE field, when it conveys a Geometric Altitude, shall be applicable as of the start of the current 1 second UTC Epoch. b. All other updated ADS-B Message fields that are provided at the ADS-B equipment input interface at least 200 milliseconds prior to the time of a scheduled ADS-B Message transmission that involves those fields, shall be reflected in the transmitted message. 2.10.2. Validation Procedure Test Date: 19 March 2004 Using a GNSS simulator, create a scenario with the following characteristics: Initial position: 45.0 degrees North, 123.0 degrees West Velocity: 100 m/s true north (approx 194 kts) NIC = 8, NACp = 7 (the non-precision condition) Record the 5 Hz position records provided by the GNSS simulator as the truth data. Apply the simulated GNSS signal to the GDL 90 unit under test. Record the transmitted ADS-B messages. Compare the truth data for the 1 Hz UTC epochs (where the seconds fraction is zero) with the transmitted position reports for at least a 5 minute period (300 epochs). The position errors should be consistent with the quantization of the position reports in UAT angular units. Note that since Latitude = -123.0 degrees can not be represented exactly in the UAT angular unit system, there will be a bias in the position error for Latitude. (-123.0 degrees converts to -- 122.999990 degrees in UAT angular units). The expected error is -0.000010 degrees The accuracy of the time of applicability of Geometric Altitude cannot be verified for the GDL 90, since its normal mode of operation is for the Altitude field to convey the Pressure Altitude. Performance is expected to be identical to that for the position data provided by the GNSS receiver. Subparagraph b is validated by analysis of the GDL 90 design. The software process that creates the transmitted ADS-B messages is designed such that the message fields are updated from the present values of the available data sources not more than 100 msec before the MSO assigned to that transmission. This guarantees that the requirements of subparagraph b are met. 16-Jan-2005 Page 29 of 41
2.10.3. Measurements & Figures Parameter Criteria Measurement Result Latitude accuracy within +/- 0.5 LSB +/- 0.5 LSB Pass Longitude accuracy within +/- 0.5 LSB +/- 0.5 LSB Pass Reported Position (not to scale) 45.6 45.5 45.4 Lat (degrees) 45.3 45.2 45.1 45 44.9-123.005-123.004-123.003-123.002-123.001-123 -122.999-122.998-122.997-122.996-122.995 Long (degrees) Figure 12 - Reported Position, non-precision Condition Figure 12 shows the Latitude and Longitude data for each transmitted ADS-B message. Position Error vs Time, Non-precision mode 0.000015 0.00001 0.000005 0 1 24 47 70 93 116 139 162 185 208 231254 277 300 323 346 369 392 415 438 461 484 507 530 553 576 599 Error (degrees) -0.000005-0.00001-0.000015 delta Lat delta Long -0.00002-0.000025-0.00003-0.000035 Time (sec) Figure 13 - Position Error, non-precision Condition 16-Jan-2005 Page 30 of 41
Figure 13 shows the difference between the true position and the reported position for each transmitted ADS-B message. Summary: As expected, the Latitude differences are randomly distributed between +/- ½ an LSB unit (+/- 0.000011 degrees). Also as expected, the Longitude differences are also within +/- ½ an LSB unit, with a bias equal to the inaccuracy of the representation of -123.0 degrees in UAT angular units. 2.10.4. Conclusion The GDL 90 meets the requirements for the Non-Precision Condition when UTC Coupled. 16-Jan-2005 Page 31 of 41
2.11. PRECISION CONDITION AND UTC COUPLED Source: draft Technical Manual 3.1.3.2 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.7.2.2 2.11.1. Requirement Text 3.1.3.2 Requirements When in Precision Condition and UTC Coupled When the UAT Transmitting Subsystem is in the Precision Condition, and is UTC Coupled: a. At the time of the ADS-B Message transmission, the position information that is encoded in the LATITUDE and LONGITUDE fields, and in the ALTITUDE field, when it conveys a Geometric Altitude, shall be applicable as of the start of the current 0.2 second UTC Epoch. b. All other updated ADS-B Message fields that are provided at the ADS-B equipment input interface at least 200 milliseconds prior to the time of a scheduled ADS-B Message transmission that involves those fields, shall be reflected in the transmitted message. 2.11.2. Validation Procedure Test Date: 30 March 2004 Using a GNSS simulator, create a scenario with the following characteristics: Initial position: 45.0 degrees North, 123.0 degrees West Velocity: 100 m/s true north (approx 194 kts) NIC = 9, NACp = 9 (the Precision condition) Record the 5 Hz position records provided by the GNSS simulator as the truth data. Apply the simulated GNSS signal to the GDL 90 unit under test. Record the transmitted ADS-B messages for at least a 5 minute period. For at least one transmitted message in each of the 5 Hz epochs, verify that the transmitted data applies to the beginning of the appropriate 5 Hz epoch. Subparagraph b is identical to the requirement for the non-precision condition, and is validated by similarity. 2.11.3. Measurements & Figures Time MSO Epoch Lat Long True Lat True Lng Lat diff Lng diff 22:17:26.00 760 0.0 45.40677-123 45.40676-123 1.1E-05 1E-05 22:14:50.00 1509 0.2 45.26719-123 45.26718-123 1E-05 3.1E-05 22:13:44.00 2204 0.4 45.20823-123 45.20822-123 5E-06 3.1E-05 22:14:13.00 3080 0.6 45.23438-123 45.23439-123 -4E-06 3.1E-05 22:14:55.00 3825 0.8 45.27219-123 45.2722-123 -7E-06 1E-05 Summary: 16-Jan-2005 Page 32 of 41
The position differences are consistent with the expected magnitudes. See 2.10 for analysis. 2.11.4. Conclusion The GDL 90 meets the requirements for the Precision condition when UTC coupled. 16-Jan-2005 Page 33 of 41
2.12. REQUIREMENTS WHEN NON-UTC COUPLED Source: draft Technical Manual 3.1.3.3 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.7.2.3 2.12.1. Requirement Text 3.1.3.3 Requirements When Non-UTC Coupled When the UAT Transmitting Subsystem is in the Non-UTC Coupled Condition, any change in an ADS-B Message field provided to the transmitter shall be reflected in any transmitted message containing that message field that is transmitted more than 1.0 second after the new value is received by the transmitter. 2.12.2. Validation Procedure Test Date: 30 March 2004 This requirement is validated by analysis of the GDL 90 design. The software process that creates the transmitted ADS-B messages is not dependant on the state of the UTC Coupled condition. Since data is provided by the GNSS receiver at a 5 Hz rate (200 milliseconds), and all non-gnss sourced data fields are updated at most 100 milliseconds before the MSO selected for the transmitted message, the minimum requirement is met. 2.12.3. Conclusion The GDL 90 meets the requirements for the non-utc Coupled condition. 16-Jan-2005 Page 34 of 41
2.13. DATA TIMEOUT Source: draft Technical Manual 3.1.3.4 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.7.2.4 2.13.1. Requirement Text 3.1.3.4 Data Timeout At the Time of Applicability for the ADS-B Message transmission, any ADS-B Message fields without an update provided to the transmitter within the Data Lifetime parameter (in seconds) of Table 3-1 shall be encoded as data unavailable in the subsequent transmitted message containing that message field. The table is recreated below with analysis for each data element. 2.13.2. Validation Procedure Test Date: March 2004 (covered by multiple test procedures performed over a range of dates). See Results column for each Input Data Element in the following table. Many of the data lifetime requirements are validated based on analysis of the source data rates, combined with the validation of the Time Registration and Latency requirements for the UTC Coupled conditions. For items listed with an asterisk (*), see the notes below the table. 2.13.3. Conclusion The GDL 90 meets the requirements for Data Lifetime for the data elements that are implemented. 16-Jan-2005 Page 35 of 41
Input Data Element Paragraph Data Lifetime (sec) Result ICAO 24-bit Address 2.1.5.1.3.1 No limit n/a Latitude 2.1.5.2.1 2 1 sec * Longitude 2.1.5.2.1 2 1 sec * Altitude Type Selection 2.1.5.2.2 60 60 sec Barometric Pressure Altitude 2.1.5.2.3 2 2 sec Geometric Altitude 2.1.5.2.3 2 1 sec NIC 2.1.5.2.4 2 1 sec Airborne/On-Ground Indication 2.1.5.2.5.1 2 2 sec North Velocity 2.1.5.2.6.1 2 1 sec East Velocity 2.1.5.2.6.3 2 1 sec Ground Speed 2.1.5.2.6.2 2 1 sec Track Angle 2.1.5.2.6.4 2 1 sec Heading 2.1.5.2.6.4 2 2 sec Barometric Vertical Rate 2.1.5.2.7.1.1 2 2 sec Geometric Vertical Rate 2.1.5.2.7.1.1 2 1 sec A/V Length and Width and POA 2.1.5.2.7.2 No limit n/a UTC 1 PPS Timing 2.1.5.2.8 2 1 sec Emitter Category 2.1.5.4.4 No limit n/a Call Sign 2.1.5.4.5 60 60 Emergency / Priority Status Selection 2.1.5.4.6 60 60 SIL 2.1.5.4.8 60 n/a * NACp 2.1.5.4.11 2 1 sec * NACv 2.1.5.4.12 2 n/a * NICbaro 2.1.5.4.13 2 n/a * CDTI Traffic Display Capability 2.1.5.4.14.1 60 60 sec TCAS Installed and Operational 2.1.5.4.14.2 60 60 sec TCAS/ACAS Resolution Advisory Flag 2.1.5.4.15.1 18 18 sec IDENT Selection 2.1.5.4.15.2 60 60 sec Receiving ATC Services Flag 2.1.5.4.15.3 60 60 sec True/Magnetic Indicator Flag 2.1.5.4.16 60 60 sec Heading / Track Indicator 2.1.5.6.1.1 60 60 sec Target Source Indicator (Horizontal) 2.1.5.6.1.2 60 n/a * Horizontal Mode Indicator) 2.1.5.6.1.3 60 n/a * Target Heading or Track Angle 2.1.5.6.1.5 60 n/a * Target Altitude Type 2.1.5.6.2.1 60 n/a * Target Source Indicator (Vertical) 2.1.5.6.2.2 60 n/a * Mode Indicator (Vertical) 2.1.5.6.2.3 60 n/a * Target Altitude Capability 2.1.5.6.2.4 60 n/a * Target Altitude 2.1.5.6.2.5 60 n/a * Radio Altitude 2.1.5.2.5.1 2 2 sec Pressure Altitude Disable 2.1.5.2.2 No limit n/a Airspeed 2.1.5.2.5.1 2 2 sec Note (*): For GNSS data sources, the measured data lifetime is stated for the non-precision condition. SIL is a constant value, and cannot be unavailable. There are no data sources for NACv and NICbaro and are therefore unavailable. The GDL 90 does not implement the requirements for the optional Target State data elements. 16-Jan-2005 Page 36 of 41
2.14. TURNAROUND TIME Source: draft Technical Manual 3.1.4.1 and 3.1.4.2 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.11.1 and 2.4.11.2 2.14.1. Requirement Text 3.1.4.1 Transmit-Receive Turnaround Time A transceiver shall be capable of switching from transmission to reception within 2 milliseconds. 3.1.4.2 Receive-Transmit Turnaround Time A transceiver shall be capable of switching from reception to transmission within 2 milliseconds. 2.14.2. Validation Procedure Test Date: 01 May 2004 These two requirements are validated by a single test procedure, which demonstrates the ability to receive two closely spaced ADS-B messages while transmitting an ADS-B message in the time delay between them. Configure the UAT Test Set to transmit Long ADS-B messages in every 5 th MSO, including MSOs 893 and 898. The duration of a Long ADS-B message is 0.40 milliseconds. The delay between the end of the 1 st message and the start of the 2 nd message is (1.25-0.40) = 0.85 milliseconds. Configure the GLD 90 unit under test to transmit a Long ADS-B message in MSO 895 (i.e. during the 0.85 millisecond delay). The delay from the end of the 1 st received message to MS) 895 is (0.50-0.40) = 0.10 milliseconds. The delay from the end of the unit under test s transmitted message to the start of the 2 nd received message is (0.75-0.40) = 0.35 milliseconds. Confirm that the UAT Test Set received the unit under test s transmitted message, and that the GDL 90 received both of the subject ADS-B test messages. 2.14.3. Measurements & Figures Parameter Criteria Measurement Result Receive to Transmit < 2.0 msec < 0.10 msec Pass Transmit to Receive < 2.0 msec < 0.35 msec Pass 2.14.4. Conclusion The GDL 90 meets the requirements for Receiver and Transmitter Turnaround Time. 16-Jan-2005 Page 37 of 41
2.15. RECEIVER TIME OF MESSAGE RECEIPT Source: draft Technical Manual 4.1.1 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.8.3.5 2.15.1. Requirement Text 4.1.1 Receiver Time of Message Receipt The receiver shall declare a Time of Message Receipt (TOMR) and include this as part of the report issued to the on-board application systems. The TOMR value shall be reported to within the parameters listed below: a. Range of at least 25 seconds expressed as seconds since GPS midnight modulo the range. b. Resolution of 100 nanoseconds or less. c. Accuracy of +/- 500 nanoseconds of the actual time of receipt for UAT equipment using either an internal, or external UTC coupled time source. d. The reported TOMR will be equal to the following quantity: seconds since the previous UTC midnight modulo the specified TOMR range. 2.15.2. Validation Procedure Test Date: 15 April 2004 Subparagraphs a, b, and d are validated by analysis of the GDL 90 data interface design. The integer seconds portion of the TOMR in elapsed seconds since UTC midnight is conveyed in a message that is output at the start of each 1 second UTC epoch. The seconds fraction is output in each ADS-B report, with a time resolution of 80 nanoseconds. The two portions can be combined by the airborne application to create the full TOMR field. Subparagraph c is validated by observing the TOMR value for an ADS-B transmission that travels over an RF propagation path of a known length (path length used is 6.9 meters). 2.15.3. Measurements & Figures Parameter Criteria Measurement Result TOMR Range and Resolution see text Analysis Pass TOMR Accuracy +/- 500 nsec -295 nsec (median value) Pass Note: 100% of TOMR values are within the required accuracy. Since this test was performed, a timing offset adjustment has minimized this time bias. See Figure 14 for the full data set. 16-Jan-2005 Page 38 of 41
TOMR Accuracy 0.0000005 0.0000004 0.0000003 0.0000002 0.0000001 Time (sec) 0 1 87 173 259 345 431 517 603 689 775 861 947 1033 1119 12051291 1377 1463 1549 16351721 1807 1893 1979-0.0000001-0.0000002-0.0000003-0.0000004-0.0000005 Figure 14 - TOMR Accuracy 2.15.4. Conclusion The GDL 90 meets the requirements for Receiver Time of Message Receipt. 16-Jan-2005 Page 39 of 41
2.16. REPORT ASSEMBLY ON RECEIPT OF MESSAGES Source: draft Technical Manual 4.1.2 and 4.1.3 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.9.1 and 2.4.9.2 2.16.1. Requirement Text 2.16.2. Validation Procedure 4.1.2 Report Assembly on Receipt of ADS-B Message Reports shall contain the following information: a. All elements of the received message payload applicable to the ADS-B report type with the range, resolution and units of each payload field preserved. b. The Time of Message Receipt ( 4.1.1) value measured by the receiver. 4.1.3 Report Assembly on Receipt of Ground Uplink Message Reports may contain the following information: a. The 432 bytes of unaltered received message payload. b. The Time of Message Receipt ( 4.1.1) value measured by the receiver. Test Date: 18 May 2004 Use the UAT Test Set to generate a stream of non-overlapping ADS-B and Ground Uplink messages at a level of -80 dbm, with the following distribution: Basic ADS-B: 140 per second Long ADS-B: 560 per second Ground Uplink: 32 per second Use the Maintenance port to verify that in each second, the GDL 90 unit under test reports the reception of at least 99% of each type of message. Subparagraph a of both requirements can be verified by analysis. The GDL 90 supports data interfaces that report the exact payload contents of all ADS-B and Ground Uplink message types. Analysis of flight tests using data recordings of the GDL 90 interfaces provides verification that the message payloads are reported without alteration, and of the validity of the TOMR values as required by each subparagraph b. 2.16.3. Measurements & Figures Parameter Criteria Measurement Result ADS-B Report Assembly Receipt of 700 700 msgs/sec Pass ADS-B msgs/sec Ground Uplink Report Assembly Receipt of 32 32 msgs/sec Pass msgs/sec Data unaltered Yes Verified Pass TOMR present Yes Verified Pass 2.16.4. Conclusion The GDL 90 meets the requirements for Report Assembly of ADS-B and Ground Uplink messages. 16-Jan-2005 Page 40 of 41
2.17. MESSAGE RECEPTION-TO-REPORT COMPLETION TIME Source: draft Technical Manual 4.1.4 RTCA/DO-282A, UAT MOPS, Equivalent: 2.4.10.4 2.17.1. Requirement Text 4.1.4 Message Reception-to-Report Completion Time All ADS-B Applicable Messages shall be output from the Report Assembly Function within 200 milliseconds of message input. All Ground Uplink Applicable Messages shall be output from the Report Assembly Function within 500 milliseconds of message input. 2.17.2. Validation Procedure Test Date: 18 May 2004 These requirements are validated by an internal self-test. The GDL 90 application software monitors the time delay between receipt of a message (as determined by the TOMR value) and the time at which report assembly is completed. While performing the report assembly tests, observe whether any report completion timing violations are detected. 2.17.3. Measurements & Figures Parameter Criteria Measurement Result ADS-B Completion Time < 200 msec No timing violations found Pass Ground Uplink Completion Time < 500 msec No timing violations found Pass 2.17.4. Conclusion The GDL 90 meets the requirements for Message Reception to Report Completion Time. 16-Jan-2005 Page 41 of 41