/*! * \file gps_l1_ca_dll_pll_tracking_cc.cc * \brief Implementation of a code DLL + carrier PLL tracking block * \author Carlos Aviles, 2010. carlos.avilesr(at)googlemail.com * Javier Arribas, 2011. jarribas(at)cttc.es * * Code DLL + carrier PLL according to the algorithms described in: * [1] K.Borre, D.M.Akos, N.Bertelsen, P.Rinder, and S.H.Jensen, * A Software-Defined GPS and Galileo Receiver. A Single-Frequency * Approach, Birkha user, 2007 * * ------------------------------------------------------------------------- * * Copyright (C) 2010-2011 (see AUTHORS file for a list of contributors) * * GNSS-SDR is a software defined Global Navigation * Satellite Systems receiver * * This file is part of GNSS-SDR. * * GNSS-SDR is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * at your option) any later version. * * GNSS-SDR is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with GNSS-SDR. If not, see . * * ------------------------------------------------------------------------- */ #include "gnss_synchro.h" #include "gps_l1_ca_dll_pll_tracking_cc.h" #include "gps_sdr_signal_processing.h" #include "tracking_discriminators.h" #include "CN_estimators.h" #include "GPS_L1_CA.h" #include "control_message_factory.h" #include #include #include #include #include "math.h" #include #include #include /*! * \todo Include in definition header file */ #define CN0_ESTIMATION_SAMPLES 10 #define MINIMUM_VALID_CN0 25 #define MAXIMUM_LOCK_FAIL_COUNTER 200 using google::LogMessage; gps_l1_ca_dll_pll_tracking_cc_sptr gps_l1_ca_dll_pll_make_tracking_cc( long if_freq, long fs_in, unsigned int vector_length, gr_msg_queue_sptr queue, bool dump, std::string dump_filename, float pll_bw_hz, float dll_bw_hz, float early_late_space_chips) { return gps_l1_ca_dll_pll_tracking_cc_sptr(new Gps_L1_Ca_Dll_Pll_Tracking_cc(if_freq, fs_in, vector_length, queue, dump, dump_filename, pll_bw_hz, dll_bw_hz, early_late_space_chips)); } void Gps_L1_Ca_Dll_Pll_Tracking_cc::forecast (int noutput_items, gr_vector_int &ninput_items_required) { ninput_items_required[0] = (int)d_vector_length*2; //set the required available samples in each call } Gps_L1_Ca_Dll_Pll_Tracking_cc::Gps_L1_Ca_Dll_Pll_Tracking_cc( long if_freq, long fs_in, unsigned int vector_length, gr_msg_queue_sptr queue, bool dump, std::string dump_filename, float pll_bw_hz, float dll_bw_hz, float early_late_space_chips) : gr_block ("Gps_L1_Ca_Dll_Pll_Tracking_cc", gr_make_io_signature (1, 1, sizeof(gr_complex)), gr_make_io_signature(1, 1, sizeof(Gnss_Synchro))) { //gr_sync_decimator ("Gps_L1_Ca_Dll_Pll_Tracking_cc", gr_make_io_signature (1, 1, sizeof(gr_complex)), // gr_make_io_signature(3, 3, sizeof(float)),vector_length) { // initialize internal vars d_queue = queue; d_dump = dump; d_if_freq = if_freq; d_fs_in = fs_in; d_vector_length = vector_length; d_dump_filename = dump_filename; // Initialize tracking ========================================== d_code_loop_filter.set_DLL_BW(dll_bw_hz); d_carrier_loop_filter.set_PLL_BW(pll_bw_hz); //--- DLL variables -------------------------------------------------------- d_early_late_spc_chips = early_late_space_chips; // Define early-late offset (in chips) // Initialization of local code replica // Get space for a vector with the C/A code replica sampled 1x/chip d_ca_code = new gr_complex[(int)GPS_L1_CA_CODE_LENGTH_CHIPS + 2]; d_carr_sign = new gr_complex[d_vector_length*2]; /* If an array is partitioned for more than one thread to operate on, * having the sub-array boundaries unaligned to cache lines could lead * to performance degradation. Here we allocate memory * (gr_comlex array of size 2*d_vector_length) aligned to cache of 16 bytes */ // todo: do something if posix_memalign fails // Get space for the resampled early / prompt / late local replicas if (posix_memalign((void**)&d_early_code, 16, d_vector_length * sizeof(gr_complex) * 2) == 0){}; if (posix_memalign((void**)&d_late_code, 16, d_vector_length * sizeof(gr_complex) * 2) == 0){}; if (posix_memalign((void**)&d_prompt_code, 16, d_vector_length * sizeof(gr_complex) * 2) == 0){}; // space for carrier wipeoff and signal baseband vectors if (posix_memalign((void**)&d_carr_sign, 16, d_vector_length * sizeof(gr_complex) * 2) == 0){}; // correlator outputs (scalar) if (posix_memalign((void**)&d_Early, 16, sizeof(gr_complex)) == 0){}; if (posix_memalign((void**)&d_Prompt, 16, sizeof(gr_complex)) == 0){}; if (posix_memalign((void**)&d_Late, 16, sizeof(gr_complex)) == 0){}; //--- Perform initializations ------------------------------ // define initial code frequency basis of NCO d_code_freq_hz = GPS_L1_CA_CODE_RATE_HZ; // define residual code phase (in chips) d_rem_code_phase_samples = 0.0; // define residual carrier phase d_rem_carr_phase_rad = 0.0; // sample synchronization d_sample_counter = 0; d_sample_counter_seconds = 0; d_acq_sample_stamp = 0; d_enable_tracking = false; d_pull_in = false; d_last_seg = 0; d_current_prn_length_samples = (int)d_vector_length; // CN0 estimation and lock detector buffers d_cn0_estimation_counter = 0; d_Prompt_buffer = new gr_complex[CN0_ESTIMATION_SAMPLES]; d_carrier_lock_test = 1; d_CN0_SNV_dB_Hz = 0; d_carrier_lock_fail_counter = 0; d_carrier_lock_threshold = 5; systemName["G"] = std::string("GPS"); systemName["R"] = std::string("GLONASS"); systemName["S"] = std::string("SBAS"); systemName["E"] = std::string("Galileo"); systemName["C"] = std::string("Compass"); } void Gps_L1_Ca_Dll_Pll_Tracking_cc::start_tracking() { /* * correct the code phase according to the delay between acq and trk */ d_acq_code_phase_samples = d_acquisition_gnss_synchro->Acq_delay_samples; d_acq_carrier_doppler_hz = d_acquisition_gnss_synchro->Acq_doppler_hz; d_acq_sample_stamp = d_acquisition_gnss_synchro->Acq_samplestamp_samples; unsigned long int acq_trk_diff_samples; float acq_trk_diff_seconds; acq_trk_diff_samples = d_sample_counter - d_acq_sample_stamp;//-d_vector_length; std::cout << "acq_trk_diff_samples=" << acq_trk_diff_samples << std::endl; acq_trk_diff_seconds = (float)acq_trk_diff_samples / (float)d_fs_in; //doppler effect // Fd=(C/(C+Vr))*F float radial_velocity; radial_velocity = (GPS_L1_FREQ_HZ + d_acq_carrier_doppler_hz)/GPS_L1_FREQ_HZ; // new chip and prn sequence periods based on acq Doppler float T_chip_mod_seconds; float T_prn_mod_seconds; float T_prn_mod_samples; d_code_freq_hz = radial_velocity * GPS_L1_CA_CODE_RATE_HZ; T_chip_mod_seconds = 1/d_code_freq_hz; T_prn_mod_seconds = T_chip_mod_seconds * GPS_L1_CA_CODE_LENGTH_CHIPS; T_prn_mod_samples = T_prn_mod_seconds * (float)d_fs_in; d_next_prn_length_samples = round(T_prn_mod_samples); float T_prn_true_seconds = GPS_L1_CA_CODE_LENGTH_CHIPS / GPS_L1_CA_CODE_RATE_HZ; float T_prn_true_samples = T_prn_true_seconds * (float)d_fs_in; float T_prn_diff_seconds; T_prn_diff_seconds = T_prn_true_seconds - T_prn_mod_seconds; float N_prn_diff; N_prn_diff = acq_trk_diff_seconds / T_prn_true_seconds; float corrected_acq_phase_samples, delay_correction_samples; corrected_acq_phase_samples = fmod((d_acq_code_phase_samples + T_prn_diff_seconds * N_prn_diff * (float)d_fs_in), T_prn_true_samples); if (corrected_acq_phase_samples < 0) { corrected_acq_phase_samples = T_prn_mod_samples + corrected_acq_phase_samples; } delay_correction_samples = d_acq_code_phase_samples - corrected_acq_phase_samples; d_acq_code_phase_samples = corrected_acq_phase_samples; d_carrier_doppler_hz = d_acq_carrier_doppler_hz; // DLL/PLL filter initialization d_carrier_loop_filter.initialize(d_carrier_doppler_hz); //initialize the carrier filter d_code_loop_filter.initialize(d_acq_code_phase_samples); //initialize the code filter // generate local reference ALWAYS starting at chip 1 (1 sample per chip) code_gen_conplex(&d_ca_code[1], d_acquisition_gnss_synchro->PRN, 0); d_ca_code[0] = d_ca_code[(int)GPS_L1_CA_CODE_LENGTH_CHIPS]; d_ca_code[(int)GPS_L1_CA_CODE_LENGTH_CHIPS + 1] = d_ca_code[1]; d_carrier_lock_fail_counter = 0; d_rem_code_phase_samples = 0; d_rem_carr_phase_rad = 0; d_rem_code_phase_samples = 0; d_next_rem_code_phase_samples = 0; d_acc_carrier_phase_rad = 0; d_code_phase_samples = d_acq_code_phase_samples; std::string sys_ = &d_acquisition_gnss_synchro->System; sys = sys_.substr(0,1); // DEBUG OUTPUT std::cout << "Tracking start on channel " << d_channel << " for satellite " << Gnss_Satellite(systemName[sys], d_acquisition_gnss_synchro->PRN) << std::endl; DLOG(INFO) << "Start tracking for satellite " << Gnss_Satellite(systemName[sys], d_acquisition_gnss_synchro->PRN) << " received" << std::endl; // enable tracking d_pull_in = true; d_enable_tracking = true; std::cout << "PULL-IN Doppler [Hz]=" << d_carrier_doppler_hz << " Code Phase correction [samples]=" << delay_correction_samples << " PULL-IN Code Phase [samples]=" << d_acq_code_phase_samples << std::endl; } void Gps_L1_Ca_Dll_Pll_Tracking_cc::update_local_code() { float tcode_chips; float rem_code_phase_chips; int associated_chip_index; int code_length_chips = (int)GPS_L1_CA_CODE_LENGTH_CHIPS; // unified loop for E, P, L code vectors rem_code_phase_chips = d_rem_code_phase_samples * (d_code_freq_hz / d_fs_in); tcode_chips = -rem_code_phase_chips; for (int i=0; itelemetry_decoder Gnss_Synchro current_synchro_data; // Fill the acquisition data current_synchro_data = *d_acquisition_gnss_synchro; const gr_complex* in = (gr_complex*) input_items[0]; //PRN start block alignement Gnss_Synchro **out = (Gnss_Synchro **) &output_items[0]; // Update the prn length based on code freq (variable) and // sampling frequency (fixed) // variable code PRN sample block size d_current_prn_length_samples = d_next_prn_length_samples; update_local_code(); update_local_carrier(); // perform Early, Prompt and Late correlation d_correlator.Carrier_wipeoff_and_EPL_volk(d_current_prn_length_samples, in, d_carr_sign, d_early_code, d_prompt_code, d_late_code, d_Early, d_Prompt, d_Late); // check for samples consistency (this should be done before in the receiver / here only if the source is a file) if (std::isnan((*d_Prompt).real()) == true or std::isnan((*d_Prompt).imag()) == true )// or std::isinf(in[i].real())==true or std::isinf(in[i].imag())==true) { const int samples_available = ninput_items[0]; d_sample_counter = d_sample_counter + samples_available; LOG_AT_LEVEL(WARNING) << "Detected NaN samples at sample number " << d_sample_counter; consume_each(samples_available); // make an output to not stop the rest of the processing blocks current_synchro_data.Prompt_I=0.0; current_synchro_data.Prompt_Q=0.0; current_synchro_data.Tracking_timestamp_secs=d_sample_counter_seconds; current_synchro_data.Carrier_phase_rads=0.0; current_synchro_data.Code_phase_secs=0.0; current_synchro_data.CN0_dB_hz=0.0; current_synchro_data.Flag_valid_tracking=false; *out[0] =current_synchro_data; return 1; } // Compute PLL error and update carrier NCO - carr_error = pll_cloop_two_quadrant_atan(*d_Prompt) / (float)GPS_TWO_PI; // Implement carrier loop filter and generate NCO command carr_nco = d_carrier_loop_filter.get_carrier_nco(carr_error); // Modify carrier freq based on NCO command d_carrier_doppler_hz = d_acq_carrier_doppler_hz + carr_nco; // Compute DLL error and update code NCO code_error = dll_nc_e_minus_l_normalized(*d_Early, *d_Late); // Implement code loop filter and generate NCO command code_nco = d_code_loop_filter.get_code_nco(code_error); // Modify code freq based on NCO command d_code_freq_hz = GPS_L1_CA_CODE_RATE_HZ - code_nco; // Update the phasestep based on code freq (variable) and // sampling frequency (fixed) d_code_phase_step_chips = d_code_freq_hz / (float)d_fs_in; //[chips] // variable code PRN sample block size float T_chip_seconds; float T_prn_seconds; float T_prn_samples; float K_blk_samples; T_chip_seconds = 1 / d_code_freq_hz; T_prn_seconds = T_chip_seconds * GPS_L1_CA_CODE_LENGTH_CHIPS; T_prn_samples = T_prn_seconds * d_fs_in; d_rem_code_phase_samples = d_next_rem_code_phase_samples; K_blk_samples = T_prn_samples + d_rem_code_phase_samples; // Update the current PRN delay (code phase in samples) float T_prn_true_seconds = GPS_L1_CA_CODE_LENGTH_CHIPS / GPS_L1_CA_CODE_RATE_HZ; float T_prn_true_samples = T_prn_true_seconds * (float)d_fs_in; d_code_phase_samples = d_code_phase_samples + T_prn_samples - T_prn_true_samples; if (d_code_phase_samples < 0) { d_code_phase_samples = T_prn_true_samples + d_code_phase_samples; } d_code_phase_samples = fmod(d_code_phase_samples, T_prn_true_samples); d_next_prn_length_samples = round(K_blk_samples); //round to a discrete samples d_next_rem_code_phase_samples = K_blk_samples - d_next_prn_length_samples; //rounding error /*! * \todo Improve the lock detection algorithm! */ // ####### CN0 ESTIMATION AND LOCK DETECTORS ###### if (d_cn0_estimation_counter < CN0_ESTIMATION_SAMPLES) { // fill buffer with prompt correlator output values d_Prompt_buffer[d_cn0_estimation_counter] = *d_Prompt; d_cn0_estimation_counter++; } else { d_cn0_estimation_counter = 0; d_CN0_SNV_dB_Hz = gps_l1_ca_CN0_SNV(d_Prompt_buffer, CN0_ESTIMATION_SAMPLES, d_fs_in); d_carrier_lock_test = carrier_lock_detector(d_Prompt_buffer, CN0_ESTIMATION_SAMPLES); // ###### TRACKING UNLOCK NOTIFICATION ##### //int tracking_message; if (d_carrier_lock_test < d_carrier_lock_threshold or d_carrier_lock_test > MINIMUM_VALID_CN0) { d_carrier_lock_fail_counter++; } else { if (d_carrier_lock_fail_counter > 0) d_carrier_lock_fail_counter--; } if (d_carrier_lock_fail_counter > MAXIMUM_LOCK_FAIL_COUNTER) { std::cout << "Channel " << d_channel << " loss of lock!" << std::endl ; //tracking_message = 3; //loss of lock //d_channel_internal_queue->push(tracking_message); ControlMessageFactory* cmf = new ControlMessageFactory(); if (d_queue != gr_msg_queue_sptr()) { d_queue->handle(cmf->GetQueueMessage(d_channel, 2)); } delete cmf; d_carrier_lock_fail_counter = 0; d_enable_tracking = false; // TODO: check if disabling tracking is consistent with the channel state machine } //std::cout<<"d_carrier_lock_fail_counter"<PRN) << ", CN0 = " << d_CN0_SNV_dB_Hz << " [dB-Hz]" << std::endl; //std::cout<<"TRK CH "<PRN) << ", CN0 = " << d_CN0_SNV_dB_Hz << " [dB-Hz]" << std::endl; //std::cout<<"TRK CH "<(d_channel)); d_dump_filename.append(".dat"); d_dump_file.exceptions (std::ifstream::failbit | std::ifstream::badbit); d_dump_file.open(d_dump_filename.c_str(), std::ios::out | std::ios::binary); std::cout << "Tracking dump enabled on channel " << d_channel << " Log file: " << d_dump_filename.c_str() << std::endl; } catch (std::ifstream::failure e) { std::cout << "channel " << d_channel << " Exception opening trk dump file " << e.what() << std::endl; } } } } void Gps_L1_Ca_Dll_Pll_Tracking_cc::set_channel_queue(concurrent_queue *channel_internal_queue) { d_channel_internal_queue = channel_internal_queue; } void Gps_L1_Ca_Dll_Pll_Tracking_cc::set_gnss_synchro(Gnss_Synchro* p_gnss_synchro) { d_acquisition_gnss_synchro = p_gnss_synchro; // Gnss_Satellite(satellite.get_system(), satellite.get_PRN()); //DLOG(INFO) << "Tracking code phase set to " << d_acq_code_phase_samples; //DLOG(INFO) << "Tracking carrier doppler set to " << d_acq_carrier_doppler_hz; //DLOG(INFO) << "Tracking Satellite set to " << d_satellite; }