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gnss-sdr/src/algorithms/acquisition/gnuradio_blocks/pcps_acquisition.cc

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/*!
* \file pcps_acquisition.cc
* \brief This class implements a Parallel Code Phase Search Acquisition
* \authors <ul>
* <li> Javier Arribas, 2011. jarribas(at)cttc.es
* <li> Luis Esteve, 2012. luis(at)epsilon-formacion.com
* <li> Marc Molina, 2013. marc.molina.pena@gmail.com
* <li> Cillian O'Driscoll, 2017. cillian(at)ieee.org
* </ul>
*
* -----------------------------------------------------------------------------
*
* GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
* This file is part of GNSS-SDR.
*
* Copyright (C) 2010-2020 (see AUTHORS file for a list of contributors)
* SPDX-License-Identifier: GPL-3.0-or-later
*
* -----------------------------------------------------------------------------
*/
#include "pcps_acquisition.h"
#include "GLONASS_L1_L2_CA.h" // for GLONASS_PRN
#include "MATH_CONSTANTS.h" // for TWO_PI
#include "gnss_frequencies.h"
#include "gnss_sdr_create_directory.h"
#include "gnss_sdr_filesystem.h"
#include "gnss_synchro.h"
#include <boost/math/special_functions/gamma.hpp>
#include <gnuradio/io_signature.h>
#include <matio.h>
#include <pmt/pmt.h> // for from_long
#include <pmt/pmt_sugar.h> // for mp
#include <volk/volk.h>
#include <volk_gnsssdr/volk_gnsssdr.h>
#include <algorithm> // for std::fill_n, std::min, std::copy
#include <array>
#include <cmath> // for floor, fmod, rint, ceil
#include <iostream>
#include <map>
#if USE_GLOG_AND_GFLAGS
#include <glog/logging.h>
#else
#include <absl/log/log.h>
#endif
pcps_acquisition_sptr pcps_make_acquisition(const Acq_Conf& conf_)
{
return pcps_acquisition_sptr(new pcps_acquisition(conf_));
}
pcps_acquisition::pcps_acquisition(const Acq_Conf& conf_)
: gr::block("pcps_acquisition",
gr::io_signature::make(1, 1, conf_.it_size),
gr::io_signature::make(0, 1, sizeof(Gnss_Synchro))),
d_acq_parameters(conf_),
d_gnss_synchro(nullptr),
d_dump_filename(conf_.dump_filename),
d_dump_number(0LL),
d_sample_counter(0ULL),
d_threshold(0.0),
d_mag(0),
d_input_power(0.0),
d_test_statistics(0.0),
d_doppler_center_step_two(0.0),
d_state(0),
d_positive_acq(0),
d_doppler_center(0U),
d_doppler_bias(0),
d_channel(0U),
d_samplesPerChip(conf_.samples_per_chip),
d_doppler_step(conf_.doppler_step),
d_num_noncoherent_integrations_counter(0U),
d_consumed_samples(conf_.sampled_ms * conf_.samples_per_ms * (conf_.bit_transition_flag ? 2.0 : 1.0)),
d_num_doppler_bins(0U),
d_num_doppler_bins_step2(conf_.num_doppler_bins_step2),
d_dump_channel(conf_.dump_channel),
d_buffer_count(0U),
d_active(false),
d_worker_active(false),
d_step_two(false),
d_use_CFAR_algorithm_flag(conf_.use_CFAR_algorithm_flag),
d_dump(conf_.dump)
{
this->message_port_register_out(pmt::mp("events"));
if (d_acq_parameters.sampled_ms == d_acq_parameters.ms_per_code)
{
d_fft_size = d_consumed_samples;
}
else
{
d_fft_size = d_consumed_samples * 2;
}
// d_fft_size = next power of two? ////
// COD:
// Experimenting with the overlap/save technique for handling bit trannsitions
// The problem: Circular correlation is asynchronous with the received code.
// In effect the first code phase used in the correlation is the current
// estimate of the code phase at the start of the input buffer. If this is 1/2
// of the code period a bit transition would move all the signal energy into
// adjacent frequency bands at +/- 1/T where T is the integration time.
//
// We can avoid this by doing linear correlation, effectively doubling the
// size of the input buffer and padding the code with zeros.
// if (d_acq_parameters.bit_transition_flag)
// {
// d_fft_size = d_consumed_samples * 2;
// d_acq_parameters.max_dwells = 1; // Activation of d_acq_parameters.bit_transition_flag invalidates the value of d_acq_parameters.max_dwells
// }
d_tmp_buffer = volk_gnsssdr::vector<float>(d_fft_size);
d_fft_codes = volk_gnsssdr::vector<std::complex<float>>(d_fft_size);
d_input_signal = volk_gnsssdr::vector<std::complex<float>>(d_fft_size);
d_fft_if = gnss_fft_fwd_make_unique(d_fft_size);
d_ifft = gnss_fft_rev_make_unique(d_fft_size);
d_grid = arma::fmat();
d_narrow_grid = arma::fmat();
if (conf_.it_size == sizeof(gr_complex))
{
d_cshort = false;
}
else
{
d_cshort = true;
}
d_data_buffer = volk_gnsssdr::vector<std::complex<float>>(d_consumed_samples);
if (d_cshort)
{
d_data_buffer_sc = volk_gnsssdr::vector<lv_16sc_t>(d_consumed_samples);
}
if (d_dump)
{
std::string dump_path;
// Get path
if (d_dump_filename.find_last_of('/') != std::string::npos)
{
const std::string dump_filename_ = d_dump_filename.substr(d_dump_filename.find_last_of('/') + 1);
dump_path = d_dump_filename.substr(0, d_dump_filename.find_last_of('/'));
d_dump_filename = dump_filename_;
}
else
{
dump_path = std::string(".");
}
if (d_dump_filename.empty())
{
d_dump_filename = "acquisition";
}
// remove extension if any
if (d_dump_filename.substr(1).find_last_of('.') != std::string::npos)
{
d_dump_filename = d_dump_filename.substr(0, d_dump_filename.find_last_of('.'));
}
d_dump_filename = dump_path + fs::path::preferred_separator + d_dump_filename;
// create directory
if (!gnss_sdr_create_directory(dump_path))
{
std::cerr << "GNSS-SDR cannot create dump file for the Acquisition block. Wrong permissions?\n";
d_dump = false;
}
}
}
void pcps_acquisition::set_resampler_latency(uint32_t latency_samples)
{
gr::thread::scoped_lock lock(d_setlock); // require mutex with work function called by the scheduler
d_acq_parameters.resampler_latency_samples = latency_samples;
}
void pcps_acquisition::set_local_code(std::complex<float>* code)
{
// This will check if it's fdma, if yes will update the intermediate frequency and the doppler grid
if (is_fdma())
{
update_grid_doppler_wipeoffs();
}
// COD
// Here we want to create a buffer that looks like this:
// [ 0 0 0 ... 0 c_0 c_1 ... c_L]
// where c_i is the local code and there are L zeros and L chips
gr::thread::scoped_lock lock(d_setlock); // require mutex with work function called by the scheduler
if (d_acq_parameters.bit_transition_flag)
{
const int32_t offset = d_fft_size / 2;
std::fill_n(d_fft_if->get_inbuf(), offset, gr_complex(0.0, 0.0));
std::copy(code, code + offset, d_fft_if->get_inbuf() + offset);
}
else
{
if (d_acq_parameters.sampled_ms == d_acq_parameters.ms_per_code)
{
std::copy(code, code + d_consumed_samples, d_fft_if->get_inbuf());
}
else
{
std::fill_n(d_fft_if->get_inbuf(), d_fft_size - d_consumed_samples, gr_complex(0.0, 0.0));
std::copy(code, code + d_consumed_samples, d_fft_if->get_inbuf() + d_consumed_samples);
}
}
d_fft_if->execute(); // We need the FFT of local code
volk_32fc_conjugate_32fc(d_fft_codes.data(), d_fft_if->get_outbuf(), d_fft_size);
}
bool pcps_acquisition::is_fdma()
{
// reset the intermediate frequency
d_doppler_bias = 0;
// Dealing with FDMA system
if (strcmp(d_gnss_synchro->Signal, "1G") == 0)
{
d_doppler_bias = static_cast<int32_t>(DFRQ1_GLO * GLONASS_PRN.at(d_gnss_synchro->PRN));
DLOG(INFO) << "Trying to acquire SV PRN " << d_gnss_synchro->PRN << " with freq " << d_doppler_bias << " in Glonass Channel " << GLONASS_PRN.at(d_gnss_synchro->PRN) << '\n';
return true;
}
if (strcmp(d_gnss_synchro->Signal, "2G") == 0)
{
d_doppler_bias += static_cast<int32_t>(DFRQ2_GLO * GLONASS_PRN.at(d_gnss_synchro->PRN));
DLOG(INFO) << "Trying to acquire SV PRN " << d_gnss_synchro->PRN << " with freq " << d_doppler_bias << " in Glonass Channel " << GLONASS_PRN.at(d_gnss_synchro->PRN) << '\n';
return true;
}
return false;
}
void pcps_acquisition::update_local_carrier(own::span<gr_complex> carrier_vector, float freq) const
{
float phase_step_rad;
if (d_acq_parameters.use_automatic_resampler)
{
phase_step_rad = static_cast<float>(TWO_PI) * freq / static_cast<float>(d_acq_parameters.resampled_fs);
}
else
{
phase_step_rad = static_cast<float>(TWO_PI) * freq / static_cast<float>(d_acq_parameters.fs_in);
}
std::array<float, 1> _phase{};
volk_gnsssdr_s32f_sincos_32fc(carrier_vector.data(), -phase_step_rad, _phase.data(), carrier_vector.size());
}
void pcps_acquisition::init()
{
d_gnss_synchro->Flag_valid_acquisition = false;
d_gnss_synchro->Flag_valid_symbol_output = false;
d_gnss_synchro->Flag_valid_pseudorange = false;
d_gnss_synchro->Flag_valid_word = false;
d_gnss_synchro->Acq_doppler_step = 0U;
d_gnss_synchro->Acq_delay_samples = 0.0;
d_gnss_synchro->Acq_doppler_hz = 0.0;
d_gnss_synchro->Acq_samplestamp_samples = 0ULL;
d_mag = 0.0;
d_input_power = 0.0;
d_num_doppler_bins = static_cast<uint32_t>(std::ceil(static_cast<double>(2 * d_acq_parameters.doppler_max) / static_cast<double>(d_doppler_step)));
// Create the carrier Doppler wipeoff signals
if (d_grid_doppler_wipeoffs.empty())
{
d_grid_doppler_wipeoffs = volk_gnsssdr::vector<volk_gnsssdr::vector<std::complex<float>>>(d_num_doppler_bins, volk_gnsssdr::vector<std::complex<float>>(d_fft_size));
}
if (d_acq_parameters.make_2_steps && (d_grid_doppler_wipeoffs_step_two.empty()))
{
d_grid_doppler_wipeoffs_step_two = volk_gnsssdr::vector<volk_gnsssdr::vector<std::complex<float>>>(d_num_doppler_bins_step2, volk_gnsssdr::vector<std::complex<float>>(d_fft_size));
}
if (d_magnitude_grid.empty())
{
d_magnitude_grid = volk_gnsssdr::vector<volk_gnsssdr::vector<float>>(d_num_doppler_bins, volk_gnsssdr::vector<float>(d_fft_size));
}
for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
{
std::fill(d_magnitude_grid[doppler_index].begin(), d_magnitude_grid[doppler_index].end(), 0.0);
}
update_grid_doppler_wipeoffs();
d_worker_active = false;
if (d_dump)
{
const uint32_t effective_fft_size = (d_acq_parameters.bit_transition_flag ? (d_fft_size / 2) : d_fft_size);
d_grid = arma::fmat(effective_fft_size, d_num_doppler_bins, arma::fill::zeros);
d_narrow_grid = arma::fmat(effective_fft_size, d_num_doppler_bins_step2, arma::fill::zeros);
}
}
void pcps_acquisition::update_grid_doppler_wipeoffs()
{
for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
{
const int32_t doppler = -static_cast<int32_t>(d_acq_parameters.doppler_max) + d_doppler_center + d_doppler_step * doppler_index;
update_local_carrier(d_grid_doppler_wipeoffs[doppler_index], static_cast<float>(d_doppler_bias + doppler));
}
}
void pcps_acquisition::update_grid_doppler_wipeoffs_step2()
{
for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins_step2; doppler_index++)
{
const float doppler = (static_cast<float>(doppler_index) - static_cast<float>(floor(d_num_doppler_bins_step2 / 2.0))) * d_acq_parameters.doppler_step2;
update_local_carrier(d_grid_doppler_wipeoffs_step_two[doppler_index], d_doppler_center_step_two + doppler);
}
}
void pcps_acquisition::set_state(int32_t state)
{
gr::thread::scoped_lock lock(d_setlock); // require mutex with work function called by the scheduler
d_state = state;
if (d_state == 1)
{
d_gnss_synchro->Acq_delay_samples = 0.0;
d_gnss_synchro->Acq_doppler_hz = 0.0;
d_gnss_synchro->Acq_samplestamp_samples = 0ULL;
d_gnss_synchro->Acq_doppler_step = 0U;
d_mag = 0.0;
d_test_statistics = 0.0;
d_active = true;
}
else if (d_state == 0)
{
}
else
{
LOG(ERROR) << "State can only be set to 0 or 1";
}
}
void pcps_acquisition::send_positive_acquisition()
{
// Declare positive acquisition using a message port
// 0=STOP_CHANNEL 1=ACQ_SUCCEES 2=ACQ_FAIL
DLOG(INFO) << "positive acquisition"
<< ", satellite " << d_gnss_synchro->System << " " << d_gnss_synchro->PRN
<< ", sample_stamp " << d_sample_counter
<< ", test statistics value " << d_test_statistics
<< ", test statistics threshold " << d_threshold
<< ", code phase " << d_gnss_synchro->Acq_delay_samples
<< ", doppler " << d_gnss_synchro->Acq_doppler_hz
<< ", magnitude " << d_mag
<< ", input signal power " << d_input_power
<< ", Assist doppler_center " << d_doppler_center;
d_positive_acq = 1;
if (!d_channel_fsm.expired())
{
// the channel FSM is set, so, notify it directly the positive acquisition to minimize delays
d_channel_fsm.lock()->Event_valid_acquisition();
}
else
{
this->message_port_pub(pmt::mp("events"), pmt::from_long(1));
}
// Copy and push current Gnss_Synchro to monitor queue
if (d_acq_parameters.enable_monitor_output)
{
Gnss_Synchro current_synchro_data = Gnss_Synchro();
current_synchro_data = *d_gnss_synchro;
d_monitor_queue.push(current_synchro_data);
}
}
void pcps_acquisition::send_negative_acquisition()
{
// Declare negative acquisition using a message port
// 0=STOP_CHANNEL 1=ACQ_SUCCEES 2=ACQ_FAIL
DLOG(INFO) << "negative acquisition"
<< ", satellite " << d_gnss_synchro->System << " " << d_gnss_synchro->PRN
<< ", sample_stamp " << d_sample_counter
<< ", test statistics value " << d_test_statistics
<< ", test statistics threshold " << d_threshold
<< ", code phase " << d_gnss_synchro->Acq_delay_samples
<< ", doppler " << d_gnss_synchro->Acq_doppler_hz
<< ", magnitude " << d_mag
<< ", input signal power " << d_input_power;
d_positive_acq = 0;
this->message_port_pub(pmt::mp("events"), pmt::from_long(2));
}
void pcps_acquisition::dump_results(int32_t effective_fft_size)
{
d_dump_number++;
std::string filename = d_dump_filename;
filename.append("_");
filename.append(1, d_gnss_synchro->System);
filename.append("_");
filename.append(1, d_gnss_synchro->Signal[0]);
filename.append(1, d_gnss_synchro->Signal[1]);
filename.append("_ch_");
filename.append(std::to_string(d_channel));
filename.append("_");
filename.append(std::to_string(d_dump_number));
filename.append("_sat_");
filename.append(std::to_string(d_gnss_synchro->PRN));
filename.append(".mat");
mat_t* matfp = Mat_CreateVer(filename.c_str(), nullptr, MAT_FT_MAT73);
if (matfp == nullptr)
{
std::cout << "Unable to create or open Acquisition dump file\n";
// d_acq_parameters.dump = false;
}
else
{
std::array<size_t, 2> dims{static_cast<size_t>(effective_fft_size), static_cast<size_t>(d_num_doppler_bins)};
matvar_t* matvar = Mat_VarCreate("acq_grid", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), d_grid.memptr(), 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
dims[0] = static_cast<size_t>(1);
dims[1] = static_cast<size_t>(1);
matvar = Mat_VarCreate("doppler_max", MAT_C_INT32, MAT_T_INT32, 1, dims.data(), &d_acq_parameters.doppler_max, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
matvar = Mat_VarCreate("doppler_step", MAT_C_INT32, MAT_T_INT32, 1, dims.data(), &d_doppler_step, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
matvar = Mat_VarCreate("d_positive_acq", MAT_C_INT32, MAT_T_INT32, 1, dims.data(), &d_positive_acq, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
auto aux = static_cast<float>(d_gnss_synchro->Acq_doppler_hz);
matvar = Mat_VarCreate("acq_doppler_hz", MAT_C_SINGLE, MAT_T_SINGLE, 1, dims.data(), &aux, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
aux = static_cast<float>(d_gnss_synchro->Acq_delay_samples);
matvar = Mat_VarCreate("acq_delay_samples", MAT_C_SINGLE, MAT_T_SINGLE, 1, dims.data(), &aux, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
matvar = Mat_VarCreate("test_statistic", MAT_C_SINGLE, MAT_T_SINGLE, 1, dims.data(), &d_test_statistics, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
matvar = Mat_VarCreate("threshold", MAT_C_SINGLE, MAT_T_SINGLE, 1, dims.data(), &d_threshold, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
matvar = Mat_VarCreate("input_power", MAT_C_SINGLE, MAT_T_SINGLE, 1, dims.data(), &d_input_power, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
matvar = Mat_VarCreate("sample_counter", MAT_C_UINT64, MAT_T_UINT64, 1, dims.data(), &d_sample_counter, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
matvar = Mat_VarCreate("PRN", MAT_C_UINT32, MAT_T_UINT32, 1, dims.data(), &d_gnss_synchro->PRN, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
matvar = Mat_VarCreate("num_dwells", MAT_C_INT32, MAT_T_INT32, 1, dims.data(), &d_num_noncoherent_integrations_counter, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
if (d_acq_parameters.make_2_steps)
{
dims[0] = static_cast<size_t>(effective_fft_size);
dims[1] = static_cast<size_t>(d_num_doppler_bins_step2);
matvar = Mat_VarCreate("acq_grid_narrow", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), d_narrow_grid.memptr(), 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
dims[0] = static_cast<size_t>(1);
dims[1] = static_cast<size_t>(1);
matvar = Mat_VarCreate("doppler_step_narrow", MAT_C_SINGLE, MAT_T_SINGLE, 1, dims.data(), &d_acq_parameters.doppler_step2, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
aux = d_doppler_center_step_two - static_cast<float>(floor(d_num_doppler_bins_step2 / 2.0)) * d_acq_parameters.doppler_step2;
matvar = Mat_VarCreate("doppler_grid_narrow_min", MAT_C_SINGLE, MAT_T_SINGLE, 1, dims.data(), &aux, 0);
Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
Mat_VarFree(matvar);
}
Mat_Close(matfp);
}
}
float pcps_acquisition::max_to_input_power_statistic(uint32_t& indext, int32_t& doppler, uint32_t num_doppler_bins, int32_t doppler_max, int32_t doppler_step)
{
float grid_maximum = 0.0;
uint32_t index_doppler = 0U;
uint32_t tmp_intex_t = 0U;
uint32_t index_time = 0U;
const int32_t effective_fft_size = (d_acq_parameters.bit_transition_flag ? d_fft_size / 2 : d_fft_size);
// Find the correlation peak and the carrier frequency
for (uint32_t i = 0; i < num_doppler_bins; i++)
{
volk_gnsssdr_32f_index_max_32u(&tmp_intex_t, d_magnitude_grid[i].data(), effective_fft_size);
if (d_magnitude_grid[i][tmp_intex_t] > grid_maximum)
{
grid_maximum = d_magnitude_grid[i][tmp_intex_t];
index_doppler = i;
index_time = tmp_intex_t;
}
}
indext = index_time;
if (!d_step_two)
{
const auto index_opp = (index_doppler + d_num_doppler_bins / 2) % d_num_doppler_bins;
d_input_power = static_cast<float>(std::accumulate(d_magnitude_grid[index_opp].data(), d_magnitude_grid[index_opp].data() + effective_fft_size, static_cast<float>(0.0)) / effective_fft_size / 2.0 / d_num_noncoherent_integrations_counter);
doppler = -static_cast<int32_t>(doppler_max) + d_doppler_center + doppler_step * static_cast<int32_t>(index_doppler);
}
else
{
doppler = static_cast<int32_t>(d_doppler_center_step_two + (static_cast<float>(index_doppler) - static_cast<float>(floor(d_num_doppler_bins_step2 / 2.0))) * d_acq_parameters.doppler_step2);
}
return grid_maximum / d_input_power;
}
float pcps_acquisition::first_vs_second_peak_statistic(uint32_t& indext, int32_t& doppler, uint32_t num_doppler_bins, int32_t doppler_max, int32_t doppler_step)
{
// Look for correlation peaks in the results
// Find the highest peak and compare it to the second highest peak
// The second peak is chosen not closer than 1 chip to the highest peak
float firstPeak = 0.0;
uint32_t index_doppler = 0U;
uint32_t tmp_intex_t = 0U;
uint32_t index_time = 0U;
// Find the correlation peak and the carrier frequency
for (uint32_t i = 0; i < num_doppler_bins; i++)
{
volk_gnsssdr_32f_index_max_32u(&tmp_intex_t, d_magnitude_grid[i].data(), d_fft_size);
if (d_magnitude_grid[i][tmp_intex_t] > firstPeak)
{
firstPeak = d_magnitude_grid[i][tmp_intex_t];
index_doppler = i;
index_time = tmp_intex_t;
}
}
indext = index_time;
if (!d_step_two)
{
doppler = -static_cast<int32_t>(doppler_max) + d_doppler_center + doppler_step * static_cast<int32_t>(index_doppler);
}
else
{
doppler = static_cast<int32_t>(d_doppler_center_step_two + (static_cast<float>(index_doppler) - static_cast<float>(floor(d_num_doppler_bins_step2 / 2.0))) * d_acq_parameters.doppler_step2);
}
// Find 1 chip wide code phase exclude range around the peak
int32_t excludeRangeIndex1 = index_time - d_samplesPerChip;
int32_t excludeRangeIndex2 = index_time + d_samplesPerChip;
// Correct code phase exclude range if the range includes array boundaries
if (excludeRangeIndex1 < 0)
{
excludeRangeIndex1 = d_fft_size + excludeRangeIndex1;
}
else if (excludeRangeIndex2 >= static_cast<int32_t>(d_fft_size))
{
excludeRangeIndex2 = excludeRangeIndex2 - d_fft_size;
}
int32_t idx = excludeRangeIndex1;
std::copy(d_magnitude_grid[index_doppler].data(), d_magnitude_grid[index_doppler].data() + d_fft_size, d_tmp_buffer.data());
do
{
d_tmp_buffer[idx] = 0.0;
idx++;
if (idx == static_cast<int32_t>(d_fft_size))
{
idx = 0;
}
}
while (idx != excludeRangeIndex2);
// Find the second highest correlation peak in the same freq. bin ---
volk_gnsssdr_32f_index_max_32u(&tmp_intex_t, d_tmp_buffer.data(), d_fft_size);
const float secondPeak = d_tmp_buffer[tmp_intex_t];
// Compute the test statistics and compare to the threshold
return firstPeak / secondPeak;
}
void pcps_acquisition::acquisition_core(uint64_t samp_count)
{
gr::thread::scoped_lock lk(d_setlock);
// Initialize acquisition algorithm
int32_t doppler = 0;
uint32_t indext = 0U;
const int32_t effective_fft_size = (d_acq_parameters.bit_transition_flag ? d_fft_size / 2 : d_fft_size);
if (d_cshort)
{
volk_gnsssdr_16ic_convert_32fc(d_data_buffer.data(), d_data_buffer_sc.data(), d_consumed_samples);
}
std::copy(d_data_buffer.data(), d_data_buffer.data() + d_consumed_samples, d_input_signal.data());
if (d_fft_size > d_consumed_samples)
{
for (uint32_t i = d_consumed_samples; i < d_fft_size; i++)
{
d_input_signal[i] = gr_complex(0.0, 0.0);
}
}
const gr_complex* in = d_input_signal.data(); // Get the input samples pointer
d_mag = 0.0;
d_num_noncoherent_integrations_counter++;
DLOG(INFO) << "Channel: " << d_channel
<< " , doing acquisition of satellite: " << d_gnss_synchro->System << " " << d_gnss_synchro->PRN
<< " ,sample stamp: " << samp_count << ", threshold: "
<< d_threshold << ", doppler_max: " << d_acq_parameters.doppler_max
<< ", doppler_step: " << d_doppler_step
<< ", use_CFAR_algorithm_flag: " << (d_use_CFAR_algorithm_flag ? "true" : "false");
if (d_acq_parameters.blocking)
{
lk.unlock();
}
// Doppler frequency grid loop
if (!d_step_two)
{
for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
{
// Remove Doppler
volk_32fc_x2_multiply_32fc(d_fft_if->get_inbuf(), in, d_grid_doppler_wipeoffs[doppler_index].data(), d_fft_size);
// Perform the FFT-based convolution (parallel time search)
// Compute the FFT of the carrier wiped--off incoming signal
d_fft_if->execute();
// Multiply carrier wiped--off, Fourier transformed incoming signal with the local FFT'd code reference
volk_32fc_x2_multiply_32fc(d_ifft->get_inbuf(), d_fft_if->get_outbuf(), d_fft_codes.data(), d_fft_size);
// Compute the inverse FFT
d_ifft->execute();
// Compute squared magnitude (and accumulate in case of non-coherent integration)
const size_t offset = (d_acq_parameters.bit_transition_flag ? effective_fft_size : 0);
if (d_num_noncoherent_integrations_counter == 1)
{
volk_32fc_magnitude_squared_32f(d_magnitude_grid[doppler_index].data(), d_ifft->get_outbuf() + offset, effective_fft_size);
}
else
{
volk_32fc_magnitude_squared_32f(d_tmp_buffer.data(), d_ifft->get_outbuf() + offset, effective_fft_size);
volk_32f_x2_add_32f(d_magnitude_grid[doppler_index].data(), d_magnitude_grid[doppler_index].data(), d_tmp_buffer.data(), effective_fft_size);
}
// Record results to file if required
if (d_dump and d_channel == d_dump_channel)
{
std::copy(d_magnitude_grid[doppler_index].data(), d_magnitude_grid[doppler_index].data() + effective_fft_size, d_grid.colptr(doppler_index));
}
}
// Compute the test statistic
if (d_use_CFAR_algorithm_flag)
{
d_test_statistics = max_to_input_power_statistic(indext, doppler, d_num_doppler_bins, d_acq_parameters.doppler_max, d_doppler_step);
}
else
{
d_test_statistics = first_vs_second_peak_statistic(indext, doppler, d_num_doppler_bins, d_acq_parameters.doppler_max, d_doppler_step);
}
if (d_acq_parameters.use_automatic_resampler)
{
// take into account the acquisition resampler ratio
d_gnss_synchro->Acq_delay_samples = static_cast<double>(std::fmod(static_cast<float>(indext), d_acq_parameters.samples_per_code)) * d_acq_parameters.resampler_ratio;
d_gnss_synchro->Acq_delay_samples -= static_cast<double>(d_acq_parameters.resampler_latency_samples); // account the resampler filter latency
d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler);
d_gnss_synchro->Acq_samplestamp_samples = rint(static_cast<double>(samp_count) * d_acq_parameters.resampler_ratio);
d_gnss_synchro->fs = d_acq_parameters.resampled_fs;
}
else
{
d_gnss_synchro->Acq_delay_samples = static_cast<double>(std::fmod(static_cast<float>(indext), d_acq_parameters.samples_per_code));
d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler);
d_gnss_synchro->Acq_samplestamp_samples = samp_count;
d_gnss_synchro->fs = d_acq_parameters.fs_in;
}
}
else
{
for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins_step2; doppler_index++)
{
volk_32fc_x2_multiply_32fc(d_fft_if->get_inbuf(), in, d_grid_doppler_wipeoffs_step_two[doppler_index].data(), d_fft_size);
// Perform the FFT-based convolution (parallel time search)
// Compute the FFT of the carrier wiped--off incoming signal
d_fft_if->execute();
// Multiply carrier wiped--off, Fourier transformed incoming signal
// with the local FFT'd code reference using SIMD operations with VOLK library
volk_32fc_x2_multiply_32fc(d_ifft->get_inbuf(), d_fft_if->get_outbuf(), d_fft_codes.data(), d_fft_size);
// compute the inverse FFT
d_ifft->execute();
const size_t offset = (d_acq_parameters.bit_transition_flag ? effective_fft_size : 0);
if (d_num_noncoherent_integrations_counter == 1)
{
volk_32fc_magnitude_squared_32f(d_magnitude_grid[doppler_index].data(), d_ifft->get_outbuf() + offset, effective_fft_size);
}
else
{
volk_32fc_magnitude_squared_32f(d_tmp_buffer.data(), d_ifft->get_outbuf() + offset, effective_fft_size);
volk_32f_x2_add_32f(d_magnitude_grid[doppler_index].data(), d_magnitude_grid[doppler_index].data(), d_tmp_buffer.data(), effective_fft_size);
}
// Record results to file if required
if (d_dump and d_channel == d_dump_channel)
{
std::copy(d_magnitude_grid[doppler_index].data(), d_magnitude_grid[doppler_index].data() + effective_fft_size, d_narrow_grid.colptr(doppler_index));
}
}
// Compute the test statistic
if (d_use_CFAR_algorithm_flag)
{
d_test_statistics = max_to_input_power_statistic(indext, doppler, d_num_doppler_bins_step2, static_cast<int32_t>(d_doppler_center_step_two - (static_cast<float>(d_num_doppler_bins_step2) / 2.0) * d_acq_parameters.doppler_step2), d_acq_parameters.doppler_step2);
}
else
{
d_test_statistics = first_vs_second_peak_statistic(indext, doppler, d_num_doppler_bins_step2, static_cast<int32_t>(d_doppler_center_step_two - (static_cast<float>(d_num_doppler_bins_step2) / 2.0) * d_acq_parameters.doppler_step2), d_acq_parameters.doppler_step2);
}
if (d_acq_parameters.use_automatic_resampler)
{
// take into account the acquisition resampler ratio
d_gnss_synchro->Acq_delay_samples = static_cast<double>(std::fmod(static_cast<float>(indext), d_acq_parameters.samples_per_code)) * d_acq_parameters.resampler_ratio;
d_gnss_synchro->Acq_delay_samples -= static_cast<double>(d_acq_parameters.resampler_latency_samples); // account the resampler filter latency
d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler);
d_gnss_synchro->Acq_samplestamp_samples = rint(static_cast<double>(samp_count) * d_acq_parameters.resampler_ratio);
d_gnss_synchro->Acq_doppler_step = d_acq_parameters.doppler_step2;
d_gnss_synchro->fs = d_acq_parameters.resampled_fs;
}
else
{
d_gnss_synchro->Acq_delay_samples = static_cast<double>(std::fmod(static_cast<float>(indext), d_acq_parameters.samples_per_code));
d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler);
d_gnss_synchro->Acq_samplestamp_samples = samp_count;
d_gnss_synchro->Acq_doppler_step = d_acq_parameters.doppler_step2;
d_gnss_synchro->fs = d_acq_parameters.fs_in;
}
}
if (d_acq_parameters.blocking)
{
lk.lock();
}
if (!d_acq_parameters.bit_transition_flag)
{
if (d_test_statistics > d_threshold)
{
d_active = false;
if (d_acq_parameters.make_2_steps)
{
if (d_step_two)
{
send_positive_acquisition();
d_step_two = false;
d_state = 0; // Positive acquisition
}
else
{
d_step_two = true; // Clear input buffer and make small grid acquisition
d_doppler_center_step_two = static_cast<float>(d_gnss_synchro->Acq_doppler_hz);
update_grid_doppler_wipeoffs_step2();
d_num_noncoherent_integrations_counter = 0;
d_positive_acq = 0;
d_state = 0;
}
calculate_threshold();
}
else
{
send_positive_acquisition();
d_state = 0; // Positive acquisition
}
}
else
{
d_buffer_count = 0;
d_state = 1;
}
if (d_num_noncoherent_integrations_counter == d_acq_parameters.max_dwells)
{
if (d_state != 0)
{
send_negative_acquisition();
}
d_state = 0;
d_active = false;
const bool was_step_two = d_step_two;
d_step_two = false;
if (was_step_two)
{
calculate_threshold();
}
}
}
else
{
d_active = false;
if (d_test_statistics > d_threshold)
{
if (d_acq_parameters.make_2_steps)
{
if (d_step_two)
{
send_positive_acquisition();
d_step_two = false;
d_state = 0; // Positive acquisition
}
else
{
d_step_two = true; // Clear input buffer and make small grid acquisition
d_doppler_center_step_two = static_cast<float>(d_gnss_synchro->Acq_doppler_hz);
update_grid_doppler_wipeoffs_step2();
d_num_noncoherent_integrations_counter = 0U;
d_state = 0;
}
calculate_threshold();
}
else
{
send_positive_acquisition();
d_state = 0; // Positive acquisition
}
}
else
{
d_state = 0; // Negative acquisition
const bool was_step_two = d_step_two;
d_step_two = false;
if (was_step_two)
{
calculate_threshold();
}
send_negative_acquisition();
}
}
d_worker_active = false;
if ((d_num_noncoherent_integrations_counter == d_acq_parameters.max_dwells) or (d_positive_acq == 1) or (d_acq_parameters.bit_transition_flag))
{
// Record results to file if required
if (d_dump and d_channel == d_dump_channel)
{
pcps_acquisition::dump_results(effective_fft_size);
}
d_num_noncoherent_integrations_counter = 0U;
d_positive_acq = 0;
}
}
// Called by gnuradio to enable drivers, etc for i/o devices.
bool pcps_acquisition::start()
{
gr::thread::scoped_lock lk(d_setlock);
d_sample_counter = 0ULL;
calculate_threshold();
return true;
}
void pcps_acquisition::calculate_threshold()
{
const float pfa = (d_step_two ? d_acq_parameters.pfa2 : d_acq_parameters.pfa);
if (pfa <= 0.0)
{
return;
}
const auto effective_fft_size = static_cast<int>(d_acq_parameters.bit_transition_flag ? (d_fft_size / 2) : d_fft_size);
const int num_doppler_bins = (d_step_two ? d_num_doppler_bins_step2 : d_num_doppler_bins);
const int num_bins = effective_fft_size * num_doppler_bins;
d_threshold = static_cast<float>(2.0 * boost::math::gamma_p_inv(2.0 * (d_acq_parameters.bit_transition_flag ? 1 : d_acq_parameters.max_dwells), std::pow(1.0 - pfa, 1.0 / static_cast<float>(num_bins))));
}
void pcps_acquisition::set_doppler_center(int32_t doppler_center)
{
gr::thread::scoped_lock lock(d_setlock); // require mutex with work function called by the scheduler
if (doppler_center != d_doppler_center)
{
DLOG(INFO) << " Doppler assistance for Channel: " << d_channel << " => Doppler: " << doppler_center << "[Hz]";
d_doppler_center = doppler_center;
update_grid_doppler_wipeoffs();
}
}
int pcps_acquisition::general_work(int noutput_items __attribute__((unused)),
gr_vector_int& ninput_items,
gr_vector_const_void_star& input_items,
gr_vector_void_star& output_items)
{
/*
* By J.Arribas, L.Esteve and M.Molina
* Acquisition strategy (Kay Borre book + CFAR threshold):
* 1. Compute the input signal power estimation
* 2. Doppler serial search loop
* 3. Perform the FFT-based circular convolution (parallel time search)
* 4. Record the maximum peak and the associated synchronization parameters
* 5. Compute the test statistics and compare to the threshold
* 6. Declare positive or negative acquisition using a message port
*/
gr::thread::scoped_lock lk(d_setlock);
if (!d_active or d_worker_active)
{
// do not consume samples while performing a non-coherent integration
bool consume_samples = ((!d_active) || (d_worker_active && (d_num_noncoherent_integrations_counter == d_acq_parameters.max_dwells)));
if ((!d_acq_parameters.blocking_on_standby) && consume_samples)
{
d_sample_counter += static_cast<uint64_t>(ninput_items[0]);
consume_each(ninput_items[0]);
}
if (d_step_two)
{
d_state = 0;
d_active = true;
}
return 0;
}
switch (d_state)
{
case 0:
{
// Restart acquisition variables
d_gnss_synchro->Acq_delay_samples = 0.0;
d_gnss_synchro->Acq_doppler_hz = 0.0;
d_gnss_synchro->Acq_samplestamp_samples = 0ULL;
d_gnss_synchro->Acq_doppler_step = 0U;
d_mag = 0.0;
d_state = 1;
d_buffer_count = 0U;
if (!d_acq_parameters.blocking_on_standby)
{
d_sample_counter += static_cast<uint64_t>(ninput_items[0]); // sample counter
consume_each(ninput_items[0]);
}
break;
}
case 1:
{
uint32_t buff_increment;
if (d_cshort)
{
const auto* in = reinterpret_cast<const lv_16sc_t*>(input_items[0]); // Get the input samples pointer
if ((ninput_items[0] + d_buffer_count) <= d_consumed_samples)
{
buff_increment = ninput_items[0];
}
else
{
buff_increment = d_consumed_samples - d_buffer_count;
}
std::copy(in, in + buff_increment, d_data_buffer_sc.begin() + d_buffer_count);
}
else
{
const auto* in = reinterpret_cast<const gr_complex*>(input_items[0]); // Get the input samples pointer
if ((ninput_items[0] + d_buffer_count) <= d_consumed_samples)
{
buff_increment = ninput_items[0];
}
else
{
buff_increment = d_consumed_samples - d_buffer_count;
}
std::copy(in, in + buff_increment, d_data_buffer.begin() + d_buffer_count);
}
// If buffer will be full in next iteration
if (d_buffer_count >= d_consumed_samples)
{
d_state = 2;
}
d_buffer_count += buff_increment;
d_sample_counter += static_cast<uint64_t>(buff_increment);
consume_each(buff_increment);
break;
}
case 2:
{
// Copy the data to the core and let it know that new data is available
if (d_acq_parameters.blocking)
{
lk.unlock();
acquisition_core(d_sample_counter);
}
else
{
gr::thread::thread d_worker(&pcps_acquisition::acquisition_core, this, d_sample_counter);
d_worker_active = true;
}
consume_each(0);
d_buffer_count = 0U;
break;
}
}
// Send outputs to the monitor
if (d_acq_parameters.enable_monitor_output)
{
auto** out = reinterpret_cast<Gnss_Synchro**>(&output_items[0]);
if (!d_monitor_queue.empty())
{
int num_gnss_synchro_objects = d_monitor_queue.size();
for (int i = 0; i < num_gnss_synchro_objects; ++i)
{
Gnss_Synchro current_synchro_data = d_monitor_queue.front();
d_monitor_queue.pop();
*out[i] = std::move(current_synchro_data);
}
return num_gnss_synchro_objects;
}
}
return 0;
}
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