Advanced Scenario Generation Test Methods

1. Advanced Scenario Generation Test Methods Proprietary & Confidential—Page 1

2. Agenda • User Command File • User Command files • MOD (Modification) Command • User Defined Data (UDD) Files Proprietary & Confidential—Page 2

3. Agenda • User Command File • User Command files • MOD (Modification) Command • User Defined Data (UDD) Files Proprietary & Confidential—Page 3

4. User Command File • What is the User Command file and what can it be used for? • The User Command File permits several SimREMOTE commands to be scripted as an ASCII text file for use during the scenario • The User Command File is a source file used by the scenario with the extension *.ucd • These commands are used for scripting various actions throughout the scenario, for instance: • Turning satellites on/off, maybe to model obscurations • Modifying signal power levels, maybe to model effects on the line of sight such as foliage or building materials • Adding multipath signals • Code/carrier divergence of the signals Proprietary & Confidential—Page 4

5. Incorporating UCD Files into SimGEN • The User Command source file is incorporated into the scenario under the Options scenario tree shown to the right • It has been available since SimGEN V2.70 • Previously only available via “remote command file” which held no scenario association • Must be Enabled in order for SimGEN to apply the commands in the User Command File • The User Command file cannot be edited within SimGEN Proprietary & Confidential—Page 5

6. Additional User Command File Information • When using commands, the User Command File should NOT contain certain scenario control SimREMOTE commands such as: • SC, RU, AR, TR, TIME, UTC_OFFSET (that make reference to the scenario) • VEH_ , ANT_ , SIG_ (that make data requests) • Motion commands should be referenced in the .umt file • The User Command File cannot be edited via a SimGEN GUI • Refer to the SimREMOTE manual for ASCII syntax of the commands • An example user command is: • 0 00:00:05,POW_ON,v1_a1,1,1,0,0,0 • Turn ON satellite SVID 1 at 5 seconds into the simulation Proprietary & Confidential—Page 6

7. Modification (MOD) Command • Some tests require more control of the signal characteristics then what is provided “out of the box” by SimGEN • These tests may require modeling: • Ionospheric scintillation • Code/Carrier divergence • Diffuse or user specified multipath • User specified Ionospheric/Tropospheric models • Any other unmodeled effects that need unique control of each satellite code, carrier and amplitude • So for where SimGEN’s default models may not be sufficient, the user can generate their own models using the “MOD” command Proprietary & Confidential—Page 7

8. Ionospheric Scintillation MOD Example • An occasional event, Ionospheric scintillation is a rapid change in signal amplitude and phase that can cause ranging and tracking errors • A rising concern in ranging accuracy, Scintillation causes pseudorange and carrier phase measurement error, and even complete loss of lock for a receiver (affect on amplitude and carrier are shown below) • This phenomena is not modeled by any of the atmospheric settings. If the user wishes to simulate Scintillation they should use the MOD command to rapidly change the signals characteristics Proprietary & Confidential—Page 8

9. MOD Command (cont.) • The MOD command is a SimREMOTE command that can be sent to SimGEN remotely or scripted locally on the SimGEN PC • Using the MOD command, the user has the powerful capability of overlaying user defined code, carrier and amplitude contributions on top of SimGEN’s calculated values • These contributions can be defined for: • Each frequency (L1, L2,L5) • Each satellite • Resolution/transmit rates at up to 100Hz • Multipath echoes • It is important to note that the MOD commands are continuously applied until updated by the user Proprietary & Confidential—Page 9

10. MOD Command Format • Similar to other SimREMOTE commands, the MOD command has: • Timestamp for specifying the time of applicable for the data in the MOD command • Specifications for which vehicle, antenna and signal type (GPS, GLONASS, etc.) to apply the modifications • Which satellite, channel, multipath echo and frequency to apply the modifications • The modifications to signal power level, carrier and code offsets • Format • <timestamp>, MOD, <veh_ant>, <signal_type>, <svid_chan_num>, <multi_index>, <mode>, <all_flag>, <freq>, <all_freq>, <sig_level>, <carr_offset>, <code_offset> Proprietary & Confidential—Page 10

11. MOD Command Example • A simple MOD command example is: • 0 00:00:10.00, MOD, v1_a1, gps, 14, 0, 0, 0, 0, 1, 3.2, 10.7, 10.65 • Timestamp, apply the modification 10 seconds into the scenario • Apply for vehicle 1, antenna 1 and GPS signal types • Apply to satellite SVID 14 only • 0 = 14 represents the SVID and not the channel • 0 = Just for this SVID and not all SVIDs • Apply the modifications: • 1 = On all frequencies • 3.2 dB increase in signal level • 10.7 m increase in carrier range • 10.65 m increase in code range Proprietary & Confidential—Page 11

12. MOD Command Example (cont.) • The MOD command is a remote command that can be sent into SimGEN for real-time manipulation of the simulated RF signals • MOD commands can be transmitted at up to 250Hz • The MOD command can be transmitted in either ASCII (shown) or binary formats (UDP) • A real-time example is shown below: • 30.00,MOD,v1_a1,gps,31,0,0,0,0,1,5,3,3 • At simulation time 30 seconds, apply a power offset of 5dB and code/carrier offsets of 3m to SVID 31 • At a 10Hz rate, update the signal level, carrier and code offsets • 30.10,MOD,v1_a1,gps,31,0,0,0,0,1,4.9,3.1,3.15 • 30.20,MOD,v1_a1,gps,31,0,0,0,0,1,4.8,3.2,3.3 • 30.30,MOD,v1_a1,gps,31,0,0,0,0,1,4.7,3.3,3.45 Proprietary & Confidential—Page 12

13. Agenda • User Command File • User Command files • MOD (Modification) Command • User Defined Data Files Proprietary & Confidential—Page 13

14. User Defined Data (UDD) Files • Typically when running a scenario: • SimGEN models the RF doppler for the satellite and vehicle/antenna motion • It also generates the satellite orbital data from a specified set of Almanac data • The almanac data is generated either from SimGEN’s default almanac or user provided YUMA, SEM, or RINEX • SimGEN adds in any Ionospheric or Tropospheric delays based on the models defined in the scenario • SimGEN can also update or modify the Nav data for causing errors or changing various data sets • So what are UDD files for? Proprietary & Confidential—Page 14

15. User Defined Data (UDD) Files (cont.) • UDD files allow the user to have much more control over what SimGEN uses for modeling various parameters such as: • Almanac • Ephemeris • Navigation Data • Genuine SV Orbits • Ionosphere and Troposphere delays • Using these files, the user has the ability to update the orbits, almanac, navigation data, use their own atmosphere models or create other unique and powerful tests • Be aware however that using UDD files can be complicated and can cause undesirable results if improperly implemented Proprietary & Confidential—Page 15

16. What are UDD Files? • Similar to the User Command files, the User Defined Data files are ASCII based and can be edited with any text editor • These files can be viewed within SimGEN if edited • There is a separate text file for each UDD selection in the scenario • The UDD features are described on the following slides and include: • Satellite Orbital Data • Satellite Ephemeris Data • Almanac Nav Data • Almanac Upload • Global Nav Data • Ionospheric Delay • Tropospheric Delay • Nav Data Modification • IEEE Control Messages Proprietary & Confidential—Page 16

17. Incorporating UDD Files in SimGEN • UDD files are added to the scenario under GPS Constellation > Enable user-defined data as shown to the right • Once UDD is enabled, one or all of the UDD files may be selected and enabled for use in the scenario • In order for the desired UDD file to be used in the scenario it has to be enabled with a ‘check’ • All file formats are described in detail in the SimGEN User Manual, Chapter 24 User-defined data (EVTP) Proprietary & Confidential—Page 17

18. Satellite Orbital Data • Used to define the motion of the simulated GPS satellites • Specifically this defines the actual motion of the SV’s that are simulated on the RF • Useful for modeling unique orbits or having divergence from the broadcast ephemeris positions in the navigation data • The ASCII text file has extension .EPH • An example is shown to the right • Consecutive ephemeris may exhibit some degree of divergence from one another with time • To avoid discontinuity when switching from one set to the next, SimGEN determines the applied satellite motion from the current ephemeris set up to a point that is one minute before a new set is applied at the cutover time Proprietary & Confidential—Page 18

19. Satellite Ephemeris Data • Used to define the broadcast Navigation Data sets for satellite ephemeris and clock parameters • Specifically this defines the content of the Navigation data and not what the RF is doing • Useful for updating the satellite orbital positions or having divergence from the simulated RF positions • The ASCII text file has extension .EPH • This file has the same format as the orbital data file • An example is shown to the right Proprietary & Confidential—Page 19

20. GPS Nav Data Extract Utility • In addition to extracting subframe data, the GPS Nav Data Extract Utility can also be used to generate *.EPH UDD files from the selected scenario • This provides the benefit of generating .EPH files for other scenarios or as a starting template for offline manipulation to generate new EPH files Proprietary & Confidential—Page 20

21. Almanac Nav Data • Used to define the broadcast almanac data for the satellite orbits • Same as the Satellite Ephemeris Data file, the data defined in the Almanac Nav Data is broadcast in the navigation message only and does not affect the RF • The user supplied almanac data for a satellite is valid throughout the run unless superseded by a user almanac upload file • The ASCII text file has extension .ALM • This file has the same format as the almanac files downloaded from the U.S. Coast Guard website: www.navcen.uscg.gov/gps/almanacs.htm • An example is shown to the right Proprietary & Confidential—Page 21

22. Almanac Upload • Used to define the broadcast almanac data for the satellite orbits after an upload • Simulates an upload of the Almanac Data • Only 1 upload (historic) • Replaces all of the previously used almanac data for each satellite • If used, must also have an Almanac Nav Data file specified • It is the responsibility of the user to ensure that the upload time for the almanac is correctly aligned with a corresponding change in ephemeris/clock data for the affected satellite • The ASCII text file has extension .ALM • This file has the same format as the Almanac Nav Data file • An example is shown to the right Proprietary & Confidential—Page 22

23. Global Nav Data • This file allows various parameters and fields in the Navigation Data message to be overwritten by user defined data • In particular the UTC parameters and ionospheric coefficients • The ionospheric coefficients defined here supersede those defined in the GPS Constellation file and so are used in the modelling of ionospheric delay, as well as for the Navigation Data. • The ASCII text file has extension .GBL • This file has the same format as the Almanac Nav Data file • An example is shown to the right Proprietary & Confidential—Page 23

24. Ionospheric Delay • Used to define the ionospheric delay characteristics over a given period for each satellite explicitly, using a simple quadratic expression Iono Delay = D + Rt + 0.5At2 • Delay (D) The ionospheric delay at the reference time (s) • Rate (R) The delay rate coefficient at the reference time (s/s) • Accel (A) The delay acceleration coefficient (s/s2) • The ASCII text file has extension .ION • An example is shown to the right • Time of Applicability (s) • SVID • Type: Explicit (1), Modeled (0) • Delay (D) • Rate (R) • Accel (A) Proprietary & Confidential—Page 24

25. Tropospheric Delay • Used to define the tropospheric delay characteristics over a given period for each satellite explicitly, using a simple quadratic expression Iono Delay = D + Rt + 0.5At2 • The application of this data is also the same as for the ionospheric data, with the Modelled mode defaulting to the particular tropospheric model specified in the atmosphere file. • The ASCII text file has extension .TRO • An example is shown to the right • Same format as Iono delay file Proprietary & Confidential—Page 25

26. Nav Data Modification • Used to overwrite selected elements of the broadcast Navigation Data message for specified satellites • Similar to the Nav data editor in the constellation file where the user-specified data overwrites the data normally generated by SimGEN • The ASCII text file has extension .NAV • An example is shown below • This is achieved by specifying the: • TOW (Z-count) to apply changes • Subframe • Page • Word • Bits to be changed • This can be applied to all or specified satellites Proprietary & Confidential—Page 26

27. IEEE Control Messages • Used to transmit commands to the signal generator hardware at specified times • This file allows GPIB (IEEE-488) or Ethernet control messages to be transmitted to GSS7700/90 and GSS8000 hardware during a run • Similar to the commands used during annual calibration • The timing and content of these messages are controlled by the user-specified file • This file is intended for internal use by Spirent • It may also be used by customers with special test requirements under the guidance/instruction of Spirent • The ASCII text file has extension .HW_MSG • An example would be a text file that has: CHAN 0 L1CO 0 • This Command would set P code only on L1 for hardware channel 0 Proprietary & Confidential—Page 27

28. How are UDD Files Used in SimGEN? • In normal operation SimGEN uses the information specified in the GPS Constellation file, atmosphere file, etc. to determine the selection and signal characteristics of the satellites to be simulated when running a scenario. • When User Defined Data is enabled for a scenario, then the information contained in these files supersedes the satellite characteristics normally applied, otherwise these are as specified by the standard SimGEN source file • For example: If only the almanac nav data was assigned, the satellite would be simulated as normal, except for the broadcast almanac data, which would be as defined in the user defined data file (*.alm). Proprietary & Confidential—Page 28