Beidou: avoid passing corrupt ephemeris and TOW measurements to observables #649
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Demonstration: https://www.youtube.com/watch?v=q4kNYVTMV3Y |
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Implement generic ephemeris validator: Keep previous and last valid ephemeris. Compare received ephemeris to previous and last valid. Count successful comparisions. Update last valid ephemeris if count reaches threshold. Add telemetry decoder configuration parameters: int32_t TelemetryDecoder_B1.ecc_reject - reject ephemeris if the ECC error counter reaches this value int32_t TelemetryDecoder_B1.ecc_resync - resync telemetry decoder if the ECC error counter reaches this value int32_t TelemetryDecoder_B1.validator_thr - number of equal ephemeris received, after that the ephemeris would be passed to observable. Set to 1 to disable validation bool TelemetryDecoder_B1.validator_accept_first - an option to always pass the first received ephemeris, bypassing the validator for one time. This may speed up first PVT solution at cost of higher probability of getting incorrect PVT in case, the first epehemeris would be corrupt. Signed-off-by: Vladislav P <vladisslav2011@gmail.com>
Signed-off-by: Vlad P <vladisslav2011@gmail.com>
Simplified telemetry decoder with better preamble synchronization. Resynchronize on bad TOW update. New telemetry decoder ecc resync/reject functionality: Count ECC errors. Reject subframe when ECC counter reaches certain threshold, defined in a configuration. New configuration parameters: TelemetryDecoder_XX.ecc_reject If the ECC error count grows past this value, reject subframe/word as corrupt TelemetryDecoder_XX.ecc_resync If the ECC error count grows past this value, reject subframe/word and restart telemetry decoder Signed-off-by: Vladislav P <vladisslav2011@gmail.com>
1. Check SOW period 2. Compare received ephemeris to last received and last valid 3. Count successful comparisions and pass ephemeris to observables only when count reaches defined threshold 4.Add BeiDou ephemeris validation configuration options: uint32_t TelemetryDecoder_B1.validator_thr = 2 - minimum number of matching ephemeris sets received before passing it to observables bool TelemetryDecoder_B1.validator_accept_first = true - always pass first ephemeris set to observables to speed up first fix at cost of possible invalid solution or delayed solution in case of weak signals/interference/jamming. Signed-off-by: Vladislav P <vladisslav2011@gmail.com>
Signed-off-by: Vladislav P <vladisslav2011@gmail.com>
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I've done some tests with real world signal and found, that BeiDou B1I/B3I telemetry decoders do not work correctly when run for some time or signal quality is far from perfect. This results in position jumps, no PVT when many satellites are tracked, completely wrong PVT using 4 satellites and weird periodic tracking shown by GNSS-SDR-Monitor.
This PR contains following fixes:
Merging this PR should fix #631
The next PR would implement similar improvements to Glonass telemetry decoder.
Documentation update pending.