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https://github.com/gnss-sdr/gnss-sdr
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Minor changes
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@ -172,7 +172,7 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
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unsigned int required_symbols = GPS_CA_PREAMBLE_LENGTH_SYMBOLS;
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d_flag_preamble = false;
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if (d_symbol_history.size() > required_symbols and d_make_correlation)
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if ((d_symbol_history.size() > required_symbols) and (d_make_correlation or !d_flag_frame_sync))
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{
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//******* preamble correlation ********
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for (unsigned int i = 0; i < GPS_CA_PREAMBLE_LENGTH_SYMBOLS; i++)
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@ -181,24 +181,22 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
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{
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if (d_symbol_history.at(i).Prompt_I < 0) // symbols clipping
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{
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corr_value -= d_preambles_symbols[i] * d_symbol_history.at(i).correlation_length_ms;
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corr_value -= d_preambles_symbols[i];
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}
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else
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{
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corr_value += d_preambles_symbols[i] * d_symbol_history.at(i).correlation_length_ms;
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corr_value += d_preambles_symbols[i];
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}
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}
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if (corr_value >= GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
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}
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if (std::abs(corr_value) >= GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
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{
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d_symbol_counter_corr = 0;
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d_make_correlation = false;
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break;
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}
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d_symbol_counter_corr++;
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}
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}
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//******* frame sync ******************
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if (abs(corr_value) == GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
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if (std::abs(corr_value) == GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
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{
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//TODO: Rewrite with state machine
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if (d_stat == 0)
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@ -215,12 +213,14 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
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}
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else if (d_stat == 1) //check 6 seconds of preamble separation
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{
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preamble_diff_ms = round(((static_cast<double>(d_symbol_history.at(0).Tracking_sample_counter) - d_preamble_time_samples) / static_cast<double>(d_symbol_history.at(0).fs)) * 1000.0);
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if (abs(preamble_diff_ms - GPS_SUBFRAME_MS) < 1)
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preamble_diff_ms = std::round(((static_cast<double>(d_symbol_history.at(0).Tracking_sample_counter) - d_preamble_time_samples) / static_cast<double>(d_symbol_history.at(0).fs)) * 1000.0);
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if (std::abs(preamble_diff_ms - GPS_SUBFRAME_MS) < 1)
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{
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DLOG(INFO) << "Preamble confirmation for SAT " << this->d_satellite;
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d_GPS_FSM.Event_gps_word_preamble();
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d_flag_preamble = true;
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d_make_correlation = false;
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d_symbol_counter_corr = 0;
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d_preamble_time_samples = d_symbol_history.at(0).Tracking_sample_counter; // record the PRN start sample index associated to the preamble
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if (!d_flag_frame_sync)
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{
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@ -245,6 +245,11 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
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}
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else
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{
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d_symbol_counter_corr++;
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if (d_symbol_counter_corr > (GPS_SUBFRAME_MS - GPS_CA_TELEMETRY_SYMBOLS_PER_BIT))
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{
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d_make_correlation = true;
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}
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if (d_stat == 1)
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{
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preamble_diff_ms = round(((static_cast<double>(d_symbol_history.at(0).Tracking_sample_counter) - static_cast<double>(d_preamble_time_samples)) / static_cast<double>(d_symbol_history.at(0).fs)) * 1000.0);
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@ -254,6 +259,8 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
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d_stat = 0; //lost of frame sync
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d_flag_frame_sync = false;
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flag_TOW_set = false;
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d_make_correlation = true;
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d_symbol_counter_corr = 0;
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}
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}
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}
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