mirror of https://github.com/gnss-sdr/gnss-sdr
450 lines
18 KiB
C++
450 lines
18 KiB
C++
/*!
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* \file pcps_tong_acquisition_cc.h
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* \brief This class implements a Parallel Code Phase Search Acquisition with
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* Tong algorithm.
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* \author Marc Molina, 2013. marc.molina.pena(at)gmail.com
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*
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* Acquisition strategy (Kaplan book + CFAR threshold).
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* <ol>
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* <li> Compute the input signal power estimation.
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* <li> Doppler serial search loop.
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* <li> Perform the FFT-based circular convolution (parallel time search).
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* <li> Compute the tests statistics for all the cells.
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* <li> Accumulate the grid of tests statistics with the previous grids.
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* <li> Record the maximum peak and the associated synchronization parameters.
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* <li> Compare the maximum averaged test statistics with a threshold.
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* <li> If the test statistics exceeds the threshold, increment the Tong counter.
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* <li> Otherwise, decrement the Tong counter.
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* <li> If the Tong counter is equal to a given maximum value, declare positive
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* <li> acquisition. If the Tong counter is equal to zero, declare negative
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* <li> acquisition. Otherwise, process the next block.
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* </ol>
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*
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* Kaplan book: D.Kaplan, J.Hegarty, "Understanding GPS. Principles
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* and Applications", Artech House, 2006, pp 223-227
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*
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* -----------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2020 (see AUTHORS file for a list of contributors)
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*
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* GNSS-SDR is a software defined Global Navigation
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* Satellite Systems receiver
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*
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* This file is part of GNSS-SDR.
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*
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* SPDX-License-Identifier: GPL-3.0-or-later
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*
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* -----------------------------------------------------------------------------
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*/
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#include "pcps_tong_acquisition_cc.h"
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#include "MATH_CONSTANTS.h" // for TWO_PI
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#include "gnss_sdr_make_unique.h"
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#include <glog/logging.h>
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#include <gnuradio/io_signature.h>
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#include <volk/volk.h>
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#include <volk_gnsssdr/volk_gnsssdr.h>
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#include <array>
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#include <exception>
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#include <sstream>
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pcps_tong_acquisition_cc_sptr pcps_tong_make_acquisition_cc(
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uint32_t sampled_ms,
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uint32_t doppler_max,
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int64_t fs_in,
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int32_t samples_per_ms,
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int32_t samples_per_code,
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uint32_t tong_init_val,
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uint32_t tong_max_val,
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uint32_t tong_max_dwells,
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bool dump,
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const std::string &dump_filename,
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bool enable_monitor_output)
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{
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return pcps_tong_acquisition_cc_sptr(
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new pcps_tong_acquisition_cc(sampled_ms, doppler_max, fs_in, samples_per_ms, samples_per_code,
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tong_init_val, tong_max_val, tong_max_dwells, dump, dump_filename, enable_monitor_output));
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}
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pcps_tong_acquisition_cc::pcps_tong_acquisition_cc(
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uint32_t sampled_ms,
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uint32_t doppler_max,
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int64_t fs_in,
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int32_t samples_per_ms,
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int32_t samples_per_code,
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uint32_t tong_init_val,
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uint32_t tong_max_val,
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uint32_t tong_max_dwells,
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bool dump,
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const std::string &dump_filename,
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bool enable_monitor_output) : gr::block("pcps_tong_acquisition_cc",
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gr::io_signature::make(1, 1, static_cast<int>(sizeof(gr_complex) * sampled_ms * samples_per_ms)),
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gr::io_signature::make(0, 1, sizeof(Gnss_Synchro)))
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{
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this->message_port_register_out(pmt::mp("events"));
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d_sample_counter = 0ULL; // SAMPLE COUNTER
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d_active = false;
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d_state = 0;
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d_fs_in = fs_in;
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d_samples_per_ms = samples_per_ms;
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d_samples_per_code = samples_per_code;
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d_sampled_ms = sampled_ms;
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d_dwell_count = 0;
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d_tong_max_val = tong_max_val;
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d_tong_max_dwells = tong_max_dwells;
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d_tong_init_val = tong_init_val;
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d_tong_count = d_tong_init_val;
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d_doppler_max = doppler_max;
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d_fft_size = d_sampled_ms * d_samples_per_ms;
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d_mag = 0;
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d_input_power = 0.0;
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d_num_doppler_bins = 0;
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d_fft_codes.reserve(d_fft_size);
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d_magnitude.reserve(d_fft_size);
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// Direct FFT
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d_fft_if = std::make_unique<gr::fft::fft_complex>(d_fft_size, true);
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// Inverse FFT
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d_ifft = std::make_unique<gr::fft::fft_complex>(d_fft_size, false);
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// For dumping samples into a file
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d_dump = dump;
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d_dump_filename = dump_filename;
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d_enable_monitor_output = enable_monitor_output;
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d_doppler_resolution = 0;
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d_threshold = 0;
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d_doppler_step = 0;
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d_gnss_synchro = nullptr;
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d_code_phase = 0;
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d_doppler_freq = 0;
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d_test_statistics = 0;
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d_channel = 0;
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}
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pcps_tong_acquisition_cc::~pcps_tong_acquisition_cc()
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{
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try
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{
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if (d_dump)
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{
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d_dump_file.close();
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}
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}
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catch (const std::ofstream::failure &e)
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{
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std::cerr << "Problem closing Acquisition dump file: " << d_dump_filename << '\n';
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}
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catch (const std::exception &e)
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{
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std::cerr << e.what() << '\n';
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}
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}
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void pcps_tong_acquisition_cc::set_local_code(std::complex<float> *code)
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{
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memcpy(d_fft_if->get_inbuf(), code, sizeof(gr_complex) * d_fft_size);
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d_fft_if->execute(); // We need the FFT of local code
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// Conjugate the local code
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volk_32fc_conjugate_32fc(d_fft_codes.data(), d_fft_if->get_outbuf(), d_fft_size);
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}
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void pcps_tong_acquisition_cc::init()
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{
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d_gnss_synchro->Flag_valid_acquisition = false;
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d_gnss_synchro->Flag_valid_symbol_output = false;
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d_gnss_synchro->Flag_valid_pseudorange = false;
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d_gnss_synchro->Flag_valid_word = false;
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d_gnss_synchro->Acq_doppler_step = 0U;
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d_gnss_synchro->Acq_delay_samples = 0.0;
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d_gnss_synchro->Acq_doppler_hz = 0.0;
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d_gnss_synchro->Acq_samplestamp_samples = 0ULL;
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d_mag = 0.0;
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d_input_power = 0.0;
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// Count the number of bins
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d_num_doppler_bins = 0;
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for (auto doppler = static_cast<int32_t>(-d_doppler_max);
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doppler <= static_cast<int32_t>(d_doppler_max);
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doppler += d_doppler_step)
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{
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d_num_doppler_bins++;
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}
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// Create the carrier Doppler wipeoff signals and allocate data grid.
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d_grid_doppler_wipeoffs = std::vector<std::vector<gr_complex>>(d_num_doppler_bins, std::vector<gr_complex>(d_fft_size));
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d_grid_data = std::vector<std::vector<float>>(d_num_doppler_bins, std::vector<float>(d_fft_size, 0.0));
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for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
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{
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int32_t doppler = -static_cast<int32_t>(d_doppler_max) + d_doppler_step * doppler_index;
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float phase_step_rad = static_cast<float>(TWO_PI) * doppler / static_cast<float>(d_fs_in);
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std::array<float, 1> _phase{};
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volk_gnsssdr_s32f_sincos_32fc(d_grid_doppler_wipeoffs[doppler_index].data(), -phase_step_rad, _phase.data(), d_fft_size);
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}
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}
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void pcps_tong_acquisition_cc::set_state(int32_t state)
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{
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d_state = state;
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if (d_state == 1)
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{
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d_gnss_synchro->Acq_delay_samples = 0.0;
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d_gnss_synchro->Acq_doppler_hz = 0.0;
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d_gnss_synchro->Acq_samplestamp_samples = 0ULL;
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d_gnss_synchro->Acq_doppler_step = 0U;
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d_dwell_count = 0;
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d_tong_count = d_tong_init_val;
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d_mag = 0.0;
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d_input_power = 0.0;
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d_test_statistics = 0.0;
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for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
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{
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for (uint32_t i = 0; i < d_fft_size; i++)
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{
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d_grid_data[doppler_index][i] = 0.0;
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}
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}
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}
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else if (d_state == 0)
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{
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}
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else
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{
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LOG(ERROR) << "State can only be set to 0 or 1";
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}
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}
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int pcps_tong_acquisition_cc::general_work(int noutput_items,
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gr_vector_int &ninput_items, gr_vector_const_void_star &input_items,
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gr_vector_void_star &output_items)
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{
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int32_t acquisition_message = -1; // 0=STOP_CHANNEL 1=ACQ_SUCCEES 2=ACQ_FAIL
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switch (d_state)
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{
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case 0:
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{
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if (d_active)
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{
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// restart acquisition variables
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d_gnss_synchro->Acq_delay_samples = 0.0;
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d_gnss_synchro->Acq_doppler_hz = 0.0;
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d_gnss_synchro->Acq_samplestamp_samples = 0ULL;
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d_gnss_synchro->Acq_doppler_step = 0U;
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d_dwell_count = 0;
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d_tong_count = d_tong_init_val;
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d_mag = 0.0;
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d_input_power = 0.0;
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d_test_statistics = 0.0;
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for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
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{
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for (uint32_t i = 0; i < d_fft_size; i++)
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{
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d_grid_data[doppler_index][i] = 0.0;
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}
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}
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d_state = 1;
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}
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d_sample_counter += static_cast<uint64_t>(d_fft_size * ninput_items[0]); // sample counter
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consume_each(ninput_items[0]);
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break;
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}
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case 1:
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{
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// initialize acquisition algorithm
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int32_t doppler;
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uint32_t indext = 0;
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float magt = 0.0;
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const auto *in = reinterpret_cast<const gr_complex *>(input_items[0]); // Get the input samples pointer
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float fft_normalization_factor = static_cast<float>(d_fft_size) * static_cast<float>(d_fft_size);
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d_input_power = 0.0;
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d_mag = 0.0;
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d_sample_counter += static_cast<uint64_t>(d_fft_size); // sample counter
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d_dwell_count++;
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DLOG(INFO) << "Channel: " << d_channel
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<< " , doing acquisition of satellite: " << d_gnss_synchro->System << " " << d_gnss_synchro->PRN
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<< " ,sample stamp: " << d_sample_counter << ", threshold: "
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<< d_threshold << ", doppler_max: " << d_doppler_max
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<< ", doppler_step: " << d_doppler_step;
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// 1- Compute the input signal power estimation
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volk_32fc_magnitude_squared_32f(d_magnitude.data(), in, d_fft_size);
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volk_32f_accumulator_s32f(&d_input_power, d_magnitude.data(), d_fft_size);
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d_input_power /= static_cast<float>(d_fft_size);
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// 2- Doppler frequency search loop
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for (uint32_t doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
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{
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// doppler search steps
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doppler = -static_cast<int32_t>(d_doppler_max) + d_doppler_step * doppler_index;
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volk_32fc_x2_multiply_32fc(d_fft_if->get_inbuf(), in,
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d_grid_doppler_wipeoffs[doppler_index].data(), d_fft_size);
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// 3- Perform the FFT-based convolution (parallel time search)
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// Compute the FFT of the carrier wiped--off incoming signal
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d_fft_if->execute();
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// Multiply carrier wiped--off, Fourier transformed incoming signal
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// with the local FFT'd code reference using SIMD operations with VOLK library
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volk_32fc_x2_multiply_32fc(d_ifft->get_inbuf(),
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d_fft_if->get_outbuf(), d_fft_codes.data(), d_fft_size);
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// compute the inverse FFT
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d_ifft->execute();
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// Compute magnitude
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volk_32fc_magnitude_squared_32f(d_magnitude.data(), d_ifft->get_outbuf(), d_fft_size);
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// Compute vector of test statistics corresponding to current doppler index.
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volk_32f_s32f_multiply_32f(d_magnitude.data(), d_magnitude.data(),
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1 / (fft_normalization_factor * fft_normalization_factor * d_input_power),
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d_fft_size);
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// Accumulate test statistics in d_grid_data.
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volk_32f_x2_add_32f(d_grid_data[doppler_index].data(), d_magnitude.data(), d_grid_data[doppler_index].data(), d_fft_size);
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// Search maximum
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volk_gnsssdr_32f_index_max_32u(&indext, d_grid_data[doppler_index].data(), d_fft_size);
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magt = d_grid_data[doppler_index][indext];
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// 4- record the maximum peak and the associated synchronization parameters
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if (d_mag < magt)
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{
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d_mag = magt;
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d_gnss_synchro->Acq_delay_samples = static_cast<double>(indext % d_samples_per_code);
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d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler);
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d_gnss_synchro->Acq_samplestamp_samples = d_sample_counter;
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d_gnss_synchro->Acq_doppler_step = d_doppler_step;
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}
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// Record results to file if required
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if (d_dump)
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{
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std::stringstream filename;
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std::streamsize n = 2 * sizeof(float) * (d_fft_size); // complex file write
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filename.str("");
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filename << "../data/test_statistics_" << d_gnss_synchro->System
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<< "_" << d_gnss_synchro->Signal[0] << d_gnss_synchro->Signal[1] << "_sat_"
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<< d_gnss_synchro->PRN << "_doppler_" << doppler << ".dat";
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d_dump_file.open(filename.str().c_str(), std::ios::out | std::ios::binary);
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d_dump_file.write(reinterpret_cast<char *>(d_ifft->get_outbuf()), n); // write directly |abs(x)|^2 in this Doppler bin?
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d_dump_file.close();
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}
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}
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// 5- Compute the test statistics and compare to the threshold
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d_test_statistics = d_mag;
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if (d_test_statistics > d_threshold * d_dwell_count)
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{
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d_tong_count++;
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if (d_tong_count == d_tong_max_val)
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{
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d_state = 2; // Positive acquisition
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}
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}
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else
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{
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d_tong_count--;
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if (d_tong_count == 0)
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{
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d_state = 3; // Negative acquisition
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}
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}
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if (d_dwell_count >= d_tong_max_dwells)
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{
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d_state = 3; // Negative acquisition
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}
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consume_each(1);
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break;
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}
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case 2:
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{
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// 6.1- Declare positive acquisition using a message port
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DLOG(INFO) << "positive acquisition";
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DLOG(INFO) << "satellite " << d_gnss_synchro->System << " " << d_gnss_synchro->PRN;
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DLOG(INFO) << "sample_stamp " << d_sample_counter;
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DLOG(INFO) << "test statistics value " << d_test_statistics;
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DLOG(INFO) << "test statistics threshold " << d_threshold;
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DLOG(INFO) << "code phase " << d_gnss_synchro->Acq_delay_samples;
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DLOG(INFO) << "doppler " << d_gnss_synchro->Acq_doppler_hz;
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DLOG(INFO) << "magnitude " << d_mag;
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DLOG(INFO) << "input signal power " << d_input_power;
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d_active = false;
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d_state = 0;
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d_sample_counter += static_cast<uint64_t>(d_fft_size * ninput_items[0]); // sample counter
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consume_each(ninput_items[0]);
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acquisition_message = 1;
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this->message_port_pub(pmt::mp("events"), pmt::from_long(acquisition_message));
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// Copy and push current Gnss_Synchro to monitor queue
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if (d_enable_monitor_output)
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{
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auto **out = reinterpret_cast<Gnss_Synchro **>(&output_items[0]);
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Gnss_Synchro current_synchro_data = Gnss_Synchro();
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current_synchro_data = *d_gnss_synchro;
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*out[0] = current_synchro_data;
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noutput_items = 1; // Number of Gnss_Synchro objects produced
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}
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break;
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}
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case 3:
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{
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// 6.2- Declare negative acquisition using a message port
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DLOG(INFO) << "negative acquisition";
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DLOG(INFO) << "satellite " << d_gnss_synchro->System << " " << d_gnss_synchro->PRN;
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DLOG(INFO) << "sample_stamp " << d_sample_counter;
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DLOG(INFO) << "test statistics value " << d_test_statistics;
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DLOG(INFO) << "test statistics threshold " << d_threshold;
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DLOG(INFO) << "code phase " << d_gnss_synchro->Acq_delay_samples;
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DLOG(INFO) << "doppler " << d_gnss_synchro->Acq_doppler_hz;
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DLOG(INFO) << "magnitude " << d_mag;
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DLOG(INFO) << "input signal power " << d_input_power;
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d_active = false;
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d_state = 0;
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d_sample_counter += static_cast<uint64_t>(d_fft_size * ninput_items[0]); // sample counter
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consume_each(ninput_items[0]);
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acquisition_message = 2;
|
|
this->message_port_pub(pmt::mp("events"), pmt::from_long(acquisition_message));
|
|
|
|
break;
|
|
}
|
|
}
|
|
|
|
return noutput_items;
|
|
}
|