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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>
*
* -------------------------------------------------------------------------
*
* Copyright (C) 2010-2019 (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 <https://www.gnu.org/licenses/>.
*
* -------------------------------------------------------------------------
*/
#include "pcps_acquisition.h"
#include "GLONASS_L1_L2_CA.h" // for GLONASS_TWO_PI
#include "GPS_L1_CA.h" // for GPS_TWO_PI
#include "gnss_frequencies.h"
#include "gnss_sdr_create_directory.h"
#include "gnss_synchro.h"
#if HAS_STD_FILESYSTEM
#if HAS_STD_FILESYSTEM_EXPERIMENTAL
#include <experimental/filesystem>
#else
#include <filesystem>
#endif
#else
#include <boost/filesystem/path.hpp>
#endif
#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 fill_n, min
#include <array>
#include <cmath> // for floor, fmod, rint, ceil
#include <cstring> // for memcpy
#include <iostream>
#include <map>
#if HAS_STD_FILESYSTEM
#if HAS_STD_FILESYSTEM_EXPERIMENTAL
namespace fs = std::experimental::filesystem;
#else
namespace fs = std::filesystem;
#endif
#else
namespace fs = boost::filesystem;
#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, 0, conf_.it_size))
{
this->message_port_register_out(pmt::mp("events"));
acq_parameters = conf_;
d_sample_counter = 0ULL; // SAMPLE COUNTER
d_active = false;
d_positive_acq = 0;
d_state = 0;
d_doppler_bias = 0;
d_num_noncoherent_integrations_counter = 0U;
d_consumed_samples = acq_parameters.sampled_ms * acq_parameters.samples_per_ms * (acq_parameters.bit_transition_flag ? 2 : 1);
if (acq_parameters.sampled_ms == 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? ////
d_mag = 0;
d_input_power = 0.0;
d_num_doppler_bins = 0U;
d_threshold = 0.0;
d_doppler_step = 0U;
d_doppler_center = 0U;
d_doppler_center_step_two = 0.0;
d_test_statistics = 0.0;
d_channel = 0U;
if (conf_.it_size == sizeof(gr_complex))
{
d_cshort = false;
}
else
{
d_cshort = true;
}
// 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 (acq_parameters.bit_transition_flag)
{
d_fft_size = d_consumed_samples * 2;
acq_parameters.max_dwells = 1; // Activation of acq_parameters.bit_transition_flag invalidates the value of acq_parameters.max_dwells
}
d_tmp_buffer = std::vector<float>(d_fft_size);
d_fft_codes = std::vector<std::complex<float>>(d_fft_size);
d_input_signal = std::vector<std::complex<float>>(d_fft_size);
// Direct FFT
d_fft_if = std::make_shared<gr::fft::fft_complex>(d_fft_size, true);
// Inverse FFT
d_ifft = std::make_shared<gr::fft::fft_complex>(d_fft_size, false);
d_gnss_synchro = nullptr;
d_worker_active = false;
d_data_buffer = std::vector<std::complex<float>>(d_consumed_samples);
if (d_cshort)
{
d_data_buffer_sc = std::vector<lv_16sc_t>(d_consumed_samples);
}
grid_ = arma::fmat();
narrow_grid_ = arma::fmat();
d_step_two = false;
d_num_doppler_bins_step2 = acq_parameters.num_doppler_bins_step2;
d_samplesPerChip = acq_parameters.samples_per_chip;
d_buffer_count = 0U;
// todo: CFAR statistic not available for non-coherent integration
if (acq_parameters.max_dwells == 1)
{
d_use_CFAR_algorithm_flag = acq_parameters.use_CFAR_algorithm_flag;
}
else
{
d_use_CFAR_algorithm_flag = false;
}
d_dump_number = 0LL;
d_dump_channel = acq_parameters.dump_channel;
d_dump = acq_parameters.dump;
d_dump_filename = acq_parameters.dump_filename;
if (d_dump)
{
std::string dump_path;
// Get path
if (d_dump_filename.find_last_of('/') != std::string::npos)
{
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?" << std::endl;
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
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 (acq_parameters.bit_transition_flag)
{
int32_t offset = d_fft_size / 2;
std::fill_n(d_fft_if->get_inbuf(), offset, gr_complex(0.0, 0.0));
memcpy(d_fft_if->get_inbuf() + offset, code, sizeof(gr_complex) * offset);
}
else
{
if (acq_parameters.sampled_ms == acq_parameters.ms_per_code)
{
memcpy(d_fft_if->get_inbuf(), code, sizeof(gr_complex) * d_consumed_samples);
}
else
{
std::fill_n(d_fft_if->get_inbuf(), d_fft_size - d_consumed_samples, gr_complex(0.0, 0.0));
memcpy(d_fft_if->get_inbuf() + d_consumed_samples, code, sizeof(gr_complex) * 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));
LOG(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) << std::endl;
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));
LOG(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) << std::endl;
return true;
}
return false;
}
void pcps_acquisition::update_local_carrier(gsl::span<gr_complex> carrier_vector, float freq)
{
float phase_step_rad;
if (acq_parameters.use_automatic_resampler)
{
phase_step_rad = GPS_TWO_PI * freq / static_cast<float>(acq_parameters.resampled_fs);
}
else
{
phase_step_rad = GPS_TWO_PI * freq / static_cast<float>(acq_parameters.fs_in);
}
std::array<float, 1> _phase{};
volk_gnsssdr_s32f_sincos_32fc(carrier_vector.data(), -phase_step_rad, _phase.data(), carrier_vector.length());
}
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>(static_cast<int32_t>(acq_parameters.doppler_max) - static_cast<int32_t>(-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 = std::vector<std::vector<std::complex<float>>>(d_num_doppler_bins, std::vector<std::complex<float>>(d_fft_size));
}
if (acq_parameters.make_2_steps && (d_grid_doppler_wipeoffs_step_two.empty()))
{
d_grid_doppler_wipeoffs_step_two = std::vector<std::vector<std::complex<float>>>(d_num_doppler_bins_step2, std::vector<std::complex<float>>(d_fft_size));
}
if (d_magnitude_grid.empty())
{
d_magnitude_grid = std::vector<std::vector<float>>(d_num_doppler_bins, std::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)
{
uint32_t effective_fft_size = (acq_parameters.bit_transition_flag ? (d_fft_size / 2) : d_fft_size);
grid_ = arma::fmat(effective_fft_size, d_num_doppler_bins, arma::fill::zeros);
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++)
{
int32_t doppler = -static_cast<int32_t>(acq_parameters.doppler_max) + d_doppler_center + d_doppler_step * doppler_index;
update_local_carrier(d_grid_doppler_wipeoffs[doppler_index], 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++)
{
float doppler = (static_cast<float>(doppler_index) - static_cast<float>(floor(d_num_doppler_bins_step2 / 2.0))) * 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_input_power = 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));
}
}
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" << std::endl;
//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(), 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(), &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 (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(), 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(), &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)) * 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, float input_power, 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;
float fft_normalization_factor = static_cast<float>(d_fft_size) * static_cast<float>(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(), d_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)
{
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))) * acq_parameters.doppler_step2);
}
float magt = grid_maximum / (fft_normalization_factor * fft_normalization_factor);
return magt / 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))) * 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;
memcpy(d_tmp_buffer.data(), d_magnitude_grid[index_doppler].data(), d_fft_size);
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);
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;
int32_t effective_fft_size = (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);
}
memcpy(d_input_signal.data(), d_data_buffer.data(), d_consumed_samples * sizeof(gr_complex));
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_input_power = 0.0;
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: " << acq_parameters.doppler_max
<< ", doppler_step: " << d_doppler_step
<< ", use_CFAR_algorithm_flag: " << (d_use_CFAR_algorithm_flag ? "true" : "false");
lk.unlock();
if (d_use_CFAR_algorithm_flag or acq_parameters.bit_transition_flag)
{
// Compute the input signal power estimation
volk_32fc_magnitude_squared_32f(d_tmp_buffer.data(), in, d_fft_size);
volk_32f_accumulator_s32f(&d_input_power, d_tmp_buffer.data(), d_fft_size);
d_input_power /= static_cast<float>(d_fft_size);
}
// 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)
size_t offset = (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)
{
memcpy(grid_.colptr(doppler_index), d_magnitude_grid[doppler_index].data(), sizeof(float) * effective_fft_size);
}
}
// Compute the test statistic
if (d_use_CFAR_algorithm_flag)
{
d_test_statistics = max_to_input_power_statistic(indext, doppler, d_input_power, d_num_doppler_bins, acq_parameters.doppler_max, d_doppler_step);
}
else
{
d_test_statistics = first_vs_second_peak_statistic(indext, doppler, d_num_doppler_bins, acq_parameters.doppler_max, d_doppler_step);
}
if (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), acq_parameters.samples_per_code)) * acq_parameters.resampler_ratio;
d_gnss_synchro->Acq_delay_samples -= static_cast<double>(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) * acq_parameters.resampler_ratio);
}
else
{
d_gnss_synchro->Acq_delay_samples = static_cast<double>(std::fmod(static_cast<float>(indext), acq_parameters.samples_per_code));
d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler);
d_gnss_synchro->Acq_samplestamp_samples = samp_count;
}
}
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();
size_t offset = (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)
{
memcpy(narrow_grid_.colptr(doppler_index), d_magnitude_grid[doppler_index].data(), sizeof(float) * effective_fft_size);
}
}
// Compute the test statistic
if (d_use_CFAR_algorithm_flag)
{
d_test_statistics = max_to_input_power_statistic(indext, doppler, d_input_power, d_num_doppler_bins_step2, static_cast<int32_t>(d_doppler_center_step_two - (static_cast<float>(d_num_doppler_bins_step2) / 2.0) * acq_parameters.doppler_step2), 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) * acq_parameters.doppler_step2), acq_parameters.doppler_step2);
}
if (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), acq_parameters.samples_per_code)) * acq_parameters.resampler_ratio;
d_gnss_synchro->Acq_delay_samples -= static_cast<double>(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) * acq_parameters.resampler_ratio);
d_gnss_synchro->Acq_doppler_step = acq_parameters.doppler_step2;
}
else
{
d_gnss_synchro->Acq_delay_samples = static_cast<double>(std::fmod(static_cast<float>(indext), 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 = acq_parameters.doppler_step2;
}
}
lk.lock();
if (!acq_parameters.bit_transition_flag)
{
if (d_test_statistics > d_threshold)
{
d_active = false;
if (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_num_noncoherent_integrations_counter = 0;
d_positive_acq = 0;
d_state = 0;
}
}
else
{
send_positive_acquisition();
d_state = 0; // Positive acquisition
}
}
else
{
d_buffer_count = 0;
d_state = 1;
}
if (d_num_noncoherent_integrations_counter == acq_parameters.max_dwells)
{
if (d_state != 0)
{
send_negative_acquisition();
}
d_state = 0;
d_active = false;
d_step_two = false;
}
}
else
{
d_active = false;
if (d_test_statistics > d_threshold)
{
if (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_num_noncoherent_integrations_counter = 0U;
d_state = 0;
}
}
else
{
send_positive_acquisition();
d_state = 0; // Positive acquisition
}
}
else
{
d_state = 0; // Negative acquisition
d_step_two = false;
send_negative_acquisition();
}
}
d_worker_active = false;
if ((d_num_noncoherent_integrations_counter == acq_parameters.max_dwells) or (d_positive_acq == 1))
{
// 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;
// Reset grid
for (uint32_t i = 0; i < d_num_doppler_bins; i++)
{
for (uint32_t k = 0; k < d_fft_size; k++)
{
d_magnitude_grid[i][k] = 0.0;
}
}
}
}
// Called by gnuradio to enable drivers, etc for i/o devices.
bool pcps_acquisition::start()
{
d_sample_counter = 0ULL;
return true;
}
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 __attribute__((unused)))
{
/*
* 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)
{
if (!acq_parameters.blocking_on_standby)
{
d_sample_counter += static_cast<uint64_t>(ninput_items[0]);
consume_each(ninput_items[0]);
}
if (d_step_two)
{
d_doppler_center_step_two = static_cast<float>(d_gnss_synchro->Acq_doppler_hz);
update_grid_doppler_wipeoffs_step2();
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_input_power = 0.0;
d_test_statistics = 0.0;
d_state = 1;
d_buffer_count = 0U;
if (!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;
}
memcpy(&d_data_buffer_sc[d_buffer_count], in, sizeof(lv_16sc_t) * buff_increment);
}
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;
}
memcpy(&d_data_buffer[d_buffer_count], in, sizeof(gr_complex) * buff_increment);
}
// 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 (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;
}
}
return 0;
}
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