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Event Data

Events can be used to introduce changes into a running scenario. Events can be used to change the power levels of satellites, to control multipath settings, and to control navigation bits, e.g. simulating bit errors in the navigation message. Events are captured in event files.

Each line of an event file describes one event, using one of the following formats:

  1. TIME {scenario | prn SATID | channel NUMBER} relpower RELPOWER
  2. TIME {scenario | prn SATID | channel NUMBER} abspower on|off|ABSPOWER
  3. TIME {prn SATID | channel NUMBER} duplicate RELRANGE RELDOPPLER RELPOWER EFFECTIVETIME [CHTARGET]
  4. TIME {prn SATID | channel NUMBER} multipath RELRANGE RANGECHANGE RANTEINTERVAL RELDOPPLER DOPPLERCHANGE DOPPLERINTERVAL RELPOWER POWERCHANGE POWERINTERVAL [INSTANCE]
  5. TIME {prn SATID | channel NUMBER} delete [INSTANCE]
  6. TIME prn SATID navbits SIGTYPE SFID PAGEID STARTBITPOS ENDBITPOS HEXSTRING REPEAT CRCFLAG PRINTFLAG

All formats begin with a time tag (TIME), which is the time of application for the event, measured as seconds passed since the scenario Start Time. Events which apply to all satellites use the scenario keyword. Events which apply to a specific satellite indicate this by specifying channel NUMBER or prn SATID values.

  • The first format, relpower, defines a change in the power level for the scenario or a satellite identified by SATID or channel number.
  • The second format, abspower, sets the absolute power for the scenario or a satellite identified by SATID or channel number
  • The third format, duplicate, generates a duplicate signal from a given satellite, using a specified delay, Doppler and power level. Duplicate channels require 60 seconds to be created, and are introduced at fixed 30-second intervals. Only 4 Duplicate satellites are allowed to be created at a time. Duplicate events closer together than 4 seconds are spread apart automatically to maintain 4 second separation.

    SBAS and Interference satellites cannot be duplicated. The optional CHTARGET parameter specifies the channel to be used. If the channel is used by a satellite, this satellite will be disabled, and the multipath satellite replaces it. If the CHTARGET parameter is not specified, the multipath satellite will be created in the first unused channel. Multipath, SBAS and interference/jamming channels cannot be duplicated.

  • The fourth format, multipath, modifies the multipath parameters of a satellite. If the satellite is not a duplicate, it becomes a duplicate satellite, which is reflected in its SATID. SBAS and interference/jamming channels cannot have their multipath parameters modified.
  • The fifth format, delete, deletes a satellite. If the satellite is not a multipath duplicate, it will typically automatically re-appear after 1 to 2 minutes. SBAS and interference/jamming channels cannot be deleted.
  • The sixth format, navbits, sets bits in a navigation message. The ENDBITPOS-STARTBITPOS+1 LSB of the HEXSTRING are used to replace the bits between STARTBITPOS and ENDBITPOS, so that the ENDBITPOS is aligned with the LSB of the HEXSTRING.

    Should ENDBITPOS-STARTBITPOS+1 > length (HEXSTRING), the HEXSTRING will be used as a repeating pattern to replace the bits between STARTBITPOS and ENDBITPOS.

    Multiple navbits events may be applied to the same message. Note that a navbits event is applied to the first message from the event TIME with the SFID and PAGEID specified in the event. For GPS the bit count starts with MSB, whereas for Glonass, the count starts with LSB. Only GPS and GLONASS are currently supported.

The units for the event parameters are:

  • TIME in seconds since scenario start time
  • SATID is a satellite ID. The format explained in protocol documentation.
  • NUMBER is the channel number. Range depends on GSG model.
  • RELPOWER relative change in power settings specified in dB
  • ABSPOWER absolute value for power settings specified in dBm
  • RELRANGE is the relative range delay in meters.
  • RELDOPPLER is the relative Doppler offset in meters/sec.
  • EFFECTIVETIME numerical number. Reserved for future use.
  • CHTARGET is the channel number to where the duplicate is put. Range depends on GSG model.
  • RANGECHANGE is the change in range over RANGEINTERVAL. Specified in meters.
  • RANGEINTERVAL is the time period in which the RANGECHANGE is updated. Specified in seconds to the tenth of seconds accuracy.
  • DOPPLERCHANGE is the change of Doppler in meters/sec.
  • DOPPLERINTERVAL is the time period in which the DOPPLERCHANGE is updated. Specified in seconds.
  • POWERCHANGE is the change in power over POWERINTERVAL. Specified in dB.
  • POWERINTERVAL is the time period in which the POWERCHANGE is updated. Specified in seconds.
  • INSTANCE identifies which instance [1..8] of SATID we want to act on. If several (duplicate) satellites exist with the same SATID, INSTANCE can be used to identify a particular duplicate satellite.
  • SIGTYPE is one of the signal types supported by the satellite. Allowed values are: L1CA, GPSL1CA, L1P, GPSL1P, L1PY, GPSL1PY, L1CAP, GPSL1CAP, L1CAPY, GPSL1CAPY, L2P, GPSL2P, L2PY, GPSL2PY, L2C, GPSL2C, L5, GPSL5, L1, GLOL1, L2, GLOL2
  • SFID is
    • a subframe ID (with GPSL1 and L2P signals)
    • a message type (with L2C and L5 signals)
    • a frame ID (with Glonass)
  • PAGEID is
    • a page ID (with GPSL1 and L2P signals)
    • 0 (not relevant) when the subframe ID is 1-3
    • 0 (not relevant) with L2C and L5 signals
    • a string idID (with Glonass).
  • STARTBITPOS, ENDBITPOS are positions of bits in a navigation message.
  • HEXSTRING is a bit pattern to be set in the message.
  • REPEAT
    • set to 0, if the modification should be applied only once
    • set to 1, if the modification should be repeated on every message.
  • CRCFLAG
    • set to 0, if CRC/parity is not to be corrected after the modification
    • set to 1, if CRC/parity needs to be corrected after the bit modification.
  • PRINTFLAG
    • set to 0, if the modified message does not to be logged (default)
    • set to 1, if the modified message needs to be logged in the execution log. Note that the message is logged only once, even if the modification is repeated on every message (repeat flag is 1).
  • PROPENV

An example event file containing all five formats with explanations is shown below:

1.0 channel 7 relpower -3
2.0 prn G32 abspower -110.5
3.0 scenario abspower off
4.0 scenario abspower on
5.0 scenario relpower 2
10.0 prn G9 duplicate 30.0 -0.01 -8.3 0
10.0 channel 6 duplicate 30.0 -0.01 -8.3 0
11.0 channel 6 multipath 35.0 0.01 1.0 0.0 0.0 0 -10.0 0.0 0
11.0 prn G9D multipath 25.0 0.01 1.5 0.0 0.0 0 -15.0 0.0 0
12.0 prn G1 navbits L1CA 1 0 77 77 1 0 0
170.0 channel 6 delete
180.0 channel G9D delete
  • 1.0 seconds into the scenario the power level of the satellite in channel 7 will be attenuated by 3.0 dB.
  • At 2.0 seconds, the absolute power for GPS PRN 32 is set to to -110.5 dBm.
  • At 3.0 seconds, the signal transmissions for all satellites are turned off.
  • At 4.0 seconds, the power settings for all signals are restored.
  • 5.0 seconds into the scenario, the power level of all satellites is increased by 2.0 dB.
  • At 10.0 seconds, a duplicate of the GPS PRN 9 satellite is created: The range of the duplicate signal is delayed by 30.0 meters, it has a Doppler offset of -0.01 m/s and a power level that is 8.3 dB lower than the original signal.
  • At 10.0 seconds, a duplicate of the satellite in channel 6 is created: The range of the duplicate signal is delayed by 30.0 meters, it has a Doppler offset of -0.01 m/s and a power level that is 8.3 dB lower than the original signal.
  • At 11.0 seconds, the multipath settings of the newly created duplicate, identified by its channel number 6, is modified: The satellite will have a 35 meter range offset, increasing with 1cm/s. It will have its power attenuated by 10 dB.
  • At 11.0 seconds, the multipath settings of the newly created duplicate, identified by its SATID ‘G9D’, are modified: The satellite will have a 25 meter range offset, increasing with 1.5cm/s. It will have its power attenuated by 15 dB.
  • After 12.0 seconds, the MSB is set to 1 in 6-bit health (bits 77-82) in the first GPS L1CA message with subframe ID 1 sent by satellite G1.
  • After 170.0 seconds the channel number 6 duplicate is deleted.
  • After 180.0 seconds the G9D duplicate is deleted.

Note: Several Events can occur at the same epoch. If so, any PRN/channel event overrules scenario events, see example below.

EXAMPLE:

The output power of channel 1 is set to -142.0 dBm, while all other channels are transmitted with an output power of -147.0 dBm.

4.0 scenario abspower -147.0

4.0 channel 1 abspower -142.0

Note also that abspower settings of events overrule the Transmit power setting specified under Options > Transmit power, while observing the external attenuation settings.

Duplicating a satellite at time 00.00 is not permitted.