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Work on the telemetry decoder to support the variable-length correlator in GPS L1 CA tracking

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This commit is contained in:
Javier Arribas
2016-03-17 18:54:41 +01:00
parent 2f61ad7c64
commit 840bb1b9a3
5 changed files with 122 additions and 132 deletions
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47
src/algorithms/tracking/gnuradio_blocks/gps_l1_ca_dll_pll_c_aid_tracking_cc.cc
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@@ -347,6 +347,8 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
d_pull_in = false;
// Fill the acquisition data
current_synchro_data = *d_acquisition_gnss_synchro;
current_synchro_data.correlation_length_ms=1;
current_synchro_data.Flag_valid_symbol_output = false;
*out[0] = current_synchro_data;
consume_each(samples_offset); //shift input to perform alignment with local replica
d_symbol_counter++;
@@ -361,13 +363,13 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
multicorrelator_cpu.set_input_output_vectors(d_correlator_outs,in);
multicorrelator_cpu.Carrier_wipeoff_multicorrelator_resampler(d_rem_carrier_phase_rad, d_carrier_phase_step_rad, d_rem_code_phase_chips, d_code_phase_step_chips, d_correlation_length_samples);
// ####### 20ms coherent intergration extension (experimental)
// keep the last 40 symbols (2 bits to detect transitions)
// ####### coherent intergration extension
// keep the last symbols
d_E_history.push_back(d_correlator_outs[0]); // save early output
d_P_history.push_back(d_correlator_outs[1]); // save prompt output
d_L_history.push_back(d_correlator_outs[2]); // save late output
if (d_P_history.size()>d_extend_correlation_ms)
if (static_cast<int>(d_P_history.size())>d_extend_correlation_ms)
{
d_E_history.pop_front();
d_P_history.pop_front();
@@ -382,7 +384,6 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
{
// compute coherent integration and enable tracking loop
// perform coherent integration using correlator output history
//gr_complex d_correlator_outs_2[3];
//std::cout<<"##### RESET COHERENT INTEGRATION ####"<<std::endl;
d_correlator_outs[0]=gr_complex(0.0,0.0);
d_correlator_outs[1]=gr_complex(0.0,0.0);
@@ -402,14 +403,11 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
std::cout<<"dll="<<d_dll_bw_hz<<" dll_n="<<d_dll_bw_narrow_hz<<" pll="<<d_pll_bw_hz<<" pll_n="<<d_pll_bw_narrow_hz<<std::endl;
}
current_synchro_data.symbol_integration_enabled=true;
// UPDATE INTEGRATION TIME
CURRENT_INTEGRATION_TIME_S = static_cast<double>(d_extend_correlation_ms)*GPS_L1_CA_CODE_PERIOD;
enable_dll_pll=true;
}else{
current_synchro_data.symbol_integration_enabled=false;
if(d_preamble_synchronized==true)
{
// continue extended coherent correlation
@@ -434,6 +432,10 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
//remnant code phase [chips]
d_rem_code_phase_chips = d_rem_code_phase_samples * (d_code_freq_chips / static_cast<double>(d_fs_in));
// UPDATE ACCUMULATED CARRIER PHASE
CORRECTED_INTEGRATION_TIME_S=(static_cast<double>(d_correlation_length_samples)/static_cast<double>(d_fs_in));
d_acc_carrier_phase_cycles -= d_carrier_doppler_hz * CORRECTED_INTEGRATION_TIME_S;
// disable tracking loop and inform telemetry decoder
enable_dll_pll=false;
}else{
@@ -444,13 +446,11 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
}
}
}else{
current_synchro_data.symbol_integration_enabled=false;
// UPDATE INTEGRATION TIME
CURRENT_INTEGRATION_TIME_S = static_cast<double>(d_correlation_length_samples) / static_cast<double>(d_fs_in);
enable_dll_pll=true;
}
// ###### end 20ms correlation extension
if (enable_dll_pll==true)
{
@@ -498,7 +498,7 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
d_correlation_length_samples = K_prn_samples + d_rem_code_phase_integer_samples; //round to a discrete samples
d_rem_code_phase_samples=d_rem_code_phase_samples-d_rem_code_phase_integer_samples;
// UPDATE REMNANT CARRIER PHASE
// UPDATE ACCUMULATED CARRIER PHASE
CORRECTED_INTEGRATION_TIME_S=(static_cast<double>(d_correlation_length_samples)/static_cast<double>(d_fs_in));
//remnant carrier phase [rad]
d_rem_carrier_phase_rad = fmod(d_rem_carrier_phase_rad + GPS_TWO_PI * d_carrier_doppler_hz * CORRECTED_INTEGRATION_TIME_S, GPS_TWO_PI);
@@ -527,13 +527,8 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
{
d_cn0_estimation_counter = 0;
// Code lock indicator
if (current_synchro_data.symbol_integration_enabled==false)
{
d_CN0_SNV_dB_Hz = cn0_svn_estimator(d_Prompt_buffer, CN0_ESTIMATION_SAMPLES, d_fs_in, GPS_L1_CA_CODE_LENGTH_CHIPS);
}else{
d_CN0_SNV_dB_Hz = cn0_svn_estimator(d_Prompt_buffer, CN0_ESTIMATION_SAMPLES, d_fs_in, GPS_L1_CA_CODE_LENGTH_CHIPS*d_extend_correlation_ms);
}
// Carrier lock indicator
d_CN0_SNV_dB_Hz = cn0_svn_estimator(d_Prompt_buffer, CN0_ESTIMATION_SAMPLES, d_fs_in, GPS_L1_CA_CODE_LENGTH_CHIPS);
// Carrier lock indicator
d_carrier_lock_test = carrier_lock_detector(d_Prompt_buffer, CN0_ESTIMATION_SAMPLES);
// Loss of lock detection
if (d_carrier_lock_test < d_carrier_lock_threshold or d_CN0_SNV_dB_Hz < MINIMUM_VALID_CN0)
@@ -569,6 +564,12 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
current_synchro_data.CN0_dB_hz = d_CN0_SNV_dB_Hz;
current_synchro_data.Flag_valid_pseudorange = false;
current_synchro_data.Flag_valid_symbol_output = true;
if (d_preamble_synchronized==true)
{
current_synchro_data.correlation_length_ms=d_extend_correlation_ms;
}else{
current_synchro_data.correlation_length_ms=1;
}
*out[0] = current_synchro_data;
}else{
//todo: fill synchronization data to produce output while coherent integration is running
@@ -579,10 +580,16 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
current_synchro_data.Tracking_timestamp_secs = (static_cast<double>(d_sample_counter) + d_rem_code_phase_samples) / static_cast<double>(d_fs_in);
// This tracking block aligns the Tracking_timestamp_secs with the start sample of the PRN, thus, Code_phase_secs=0
current_synchro_data.Code_phase_secs = 0;
current_synchro_data.Carrier_phase_rads = GPS_TWO_PI * d_acc_carrier_phase_cycles; // todo: project the acc carrier phase
current_synchro_data.Carrier_phase_rads = GPS_TWO_PI * d_acc_carrier_phase_cycles;
current_synchro_data.Carrier_Doppler_hz = d_carrier_doppler_hz;// todo: project the carrier doppler
current_synchro_data.CN0_dB_hz = d_CN0_SNV_dB_Hz;
current_synchro_data.Flag_valid_pseudorange = false;
if (d_preamble_synchronized==true)
{
current_synchro_data.correlation_length_ms=d_extend_correlation_ms;
}else{
current_synchro_data.correlation_length_ms=1;
}
*out[0] = current_synchro_data;
}
@@ -597,7 +604,7 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
{
d_last_seg = floor(d_sample_counter / d_fs_in);
std::cout << "Current input signal time = " << d_last_seg << " [s]" << std::endl;
std::cout << "GPS L1 C/A Tracking CH " << d_channel << ": Satellite " << Gnss_Satellite(systemName[sys], d_acquisition_gnss_synchro->PRN)
DLOG(INFO) << "GPS L1 C/A Tracking CH " << d_channel << ": Satellite " << Gnss_Satellite(systemName[sys], d_acquisition_gnss_synchro->PRN)
<< ", CN0 = " << d_CN0_SNV_dB_Hz << " [dB-Hz]" << std::endl;
//if (d_last_seg==5) d_carrier_lock_fail_counter=500; //DEBUG: force unlock!
}
@@ -607,7 +614,7 @@ int gps_l1_ca_dll_pll_c_aid_tracking_cc::general_work (int noutput_items, gr_vec
if (floor(d_sample_counter / d_fs_in) != d_last_seg)
{
d_last_seg = floor(d_sample_counter / d_fs_in);
std::cout << "Tracking CH " << d_channel << ": Satellite " << Gnss_Satellite(systemName[sys], d_acquisition_gnss_synchro->PRN)
DLOG(INFO) << "Tracking CH " << d_channel << ": Satellite " << Gnss_Satellite(systemName[sys], d_acquisition_gnss_synchro->PRN)
<< ", CN0 = " << d_CN0_SNV_dB_Hz << " [dB-Hz]";
}
}