mirror of https://github.com/gnss-sdr/gnss-sdr
488 lines
20 KiB
C++
488 lines
20 KiB
C++
/*!
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* \file pcps_acquisition_sc.cc
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* \brief This class implements a Parallel Code Phase Search Acquisition
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* \authors <ul>
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* <li> Javier Arribas, 2011. jarribas(at)cttc.es
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* <li> Luis Esteve, 2012. luis(at)epsilon-formacion.com
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* <li> Marc Molina, 2013. marc.molina.pena@gmail.com
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* </ul>
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*
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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2015 (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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* GNSS-SDR is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GNSS-SDR is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
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*
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* -------------------------------------------------------------------------
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*/
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#include "pcps_acquisition_sc.h"
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#include <sstream>
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#include <boost/filesystem.hpp>
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#include <gnuradio/io_signature.h>
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#include <glog/logging.h>
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#include <volk/volk.h>
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#include <volk_gnsssdr/volk_gnsssdr.h>
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#include "control_message_factory.h"
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#include "GPS_L1_CA.h" //GPS_TWO_PI
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using google::LogMessage;
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pcps_acquisition_sc_sptr pcps_make_acquisition_sc(
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unsigned int sampled_ms, unsigned int max_dwells,
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unsigned int doppler_max, long freq, long fs_in,
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int samples_per_ms, int samples_per_code,
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bool bit_transition_flag, bool use_CFAR_algorithm_flag,
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bool dump,
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std::string dump_filename)
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{
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return pcps_acquisition_sc_sptr(
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new pcps_acquisition_sc(sampled_ms, max_dwells, doppler_max, freq, fs_in, samples_per_ms,
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samples_per_code, bit_transition_flag, use_CFAR_algorithm_flag, dump, dump_filename));
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}
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pcps_acquisition_sc::pcps_acquisition_sc(
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unsigned int sampled_ms, unsigned int max_dwells,
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unsigned int doppler_max, long freq, long fs_in,
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int samples_per_ms, int samples_per_code,
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bool bit_transition_flag, bool use_CFAR_algorithm_flag,
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bool dump,
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std::string dump_filename) :
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gr::block("pcps_acquisition_sc",
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gr::io_signature::make(1, 1, sizeof(lv_16sc_t) * sampled_ms * samples_per_ms * ( bit_transition_flag ? 2 : 1 )),
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gr::io_signature::make(0, 0, 0))
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{
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d_sample_counter = 0; // SAMPLE COUNTER
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d_active = false;
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d_state = 0;
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d_freq = freq;
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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_max_dwells = max_dwells;
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d_well_count = 0;
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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_bit_transition_flag = bit_transition_flag;
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d_use_CFAR_algorithm_flag = use_CFAR_algorithm_flag;
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d_threshold = 0.0;
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d_doppler_step = 250;
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d_code_phase = 0;
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d_test_statistics = 0.0;
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d_channel = 0;
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d_doppler_freq = 0.0;
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//set_relative_rate( 1.0/d_fft_size );
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// COD:
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// Experimenting with the overlap/save technique for handling bit trannsitions
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// The problem: Circular correlation is asynchronous with the received code.
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// In effect the first code phase used in the correlation is the current
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// estimate of the code phase at the start of the input buffer. If this is 1/2
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// of the code period a bit transition would move all the signal energy into
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// adjacent frequency bands at +/- 1/T where T is the integration time.
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//
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// We can avoid this by doing linear correlation, effectively doubling the
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// size of the input buffer and padding the code with zeros.
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if( d_bit_transition_flag )
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{
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d_fft_size *= 2;
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d_max_dwells = 1;
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}
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d_fft_codes = static_cast<gr_complex*>(volk_malloc(d_fft_size * sizeof(gr_complex), volk_get_alignment()));
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d_magnitude = static_cast<float*>(volk_malloc(d_fft_size * sizeof(float), volk_get_alignment()));
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//temporary storage for the input conversion from 16sc to float 32fc
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d_in_32fc = static_cast<gr_complex*>(volk_malloc(d_fft_size * sizeof(gr_complex), volk_get_alignment()));
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// Direct FFT
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d_fft_if = new gr::fft::fft_complex(d_fft_size, true);
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// Inverse FFT
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d_ifft = new 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_gnss_synchro = 0;
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d_grid_doppler_wipeoffs = 0;
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}
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pcps_acquisition_sc::~pcps_acquisition_sc()
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{
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if (d_num_doppler_bins > 0)
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{
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for (unsigned int i = 0; i < d_num_doppler_bins; i++)
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{
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volk_free(d_grid_doppler_wipeoffs[i]);
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}
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delete[] d_grid_doppler_wipeoffs;
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}
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volk_free(d_fft_codes);
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volk_free(d_magnitude);
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volk_free(d_in_32fc);
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delete d_ifft;
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delete d_fft_if;
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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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void pcps_acquisition_sc::set_local_code(std::complex<float> * code)
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{
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// COD
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// Here we want to create a buffer that looks like this:
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// [ 0 0 0 ... 0 c_0 c_1 ... c_L]
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// where c_i is the local code and there are L zeros and L chips
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int offset = 0;
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if( d_bit_transition_flag )
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{
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std::fill_n( d_fft_if->get_inbuf(), d_samples_per_code, gr_complex( 0.0, 0.0 ) );
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offset = d_samples_per_code;
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}
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memcpy(d_fft_if->get_inbuf() + offset, code, sizeof(gr_complex) * d_samples_per_code);
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d_fft_if->execute(); // We need the FFT of local code
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volk_32fc_conjugate_32fc(d_fft_codes, d_fft_if->get_outbuf(), d_fft_size);
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}
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void pcps_acquisition_sc::update_local_carrier(gr_complex* carrier_vector, int correlator_length_samples, float freq)
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{
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float phase_step_rad = GPS_TWO_PI * freq / static_cast<float>(d_fs_in);
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float _phase[1];
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_phase[0] = 0;
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volk_gnsssdr_s32f_sincos_32fc(carrier_vector, - phase_step_rad, _phase, correlator_length_samples);
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}
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void pcps_acquisition_sc::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->Flag_preamble = false;
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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 = 0;
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d_mag = 0.0;
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d_input_power = 0.0;
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d_num_doppler_bins = ceil( static_cast<double>(static_cast<int>(d_doppler_max) - static_cast<int>(-d_doppler_max)) / static_cast<double>(d_doppler_step));
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// Create the carrier Doppler wipeoff signals
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d_grid_doppler_wipeoffs = new gr_complex*[d_num_doppler_bins];
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for (unsigned int doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
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{
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d_grid_doppler_wipeoffs[doppler_index] = static_cast<gr_complex*>(volk_malloc(d_fft_size * sizeof(gr_complex), volk_get_alignment()));
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int doppler = -static_cast<int>(d_doppler_max) + d_doppler_step * doppler_index;
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update_local_carrier(d_grid_doppler_wipeoffs[doppler_index], d_fft_size, d_freq + doppler);
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}
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}
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void pcps_acquisition_sc::set_state(int 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 = 0;
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d_well_count = 0;
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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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}
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else if (d_state == 0)
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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_acquisition_sc::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 __attribute__((unused)))
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{
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/*
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* By J.Arribas, L.Esteve and M.Molina
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* Acquisition strategy (Kay Borre book + CFAR threshold):
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* 1. Compute the input signal power estimation
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* 2. Doppler serial search loop
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* 3. Perform the FFT-based circular convolution (parallel time search)
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* 4. Record the maximum peak and the associated synchronization parameters
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* 5. Compute the test statistics and compare to the threshold
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* 6. Declare positive or negative acquisition using a message queue
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*/
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int 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 = 0;
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d_well_count = 0;
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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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d_state = 1;
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}
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d_sample_counter += d_fft_size * ninput_items[0]; // sample counter
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consume_each(ninput_items[0]);
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//DLOG(INFO) << "Consumed " << ninput_items[0] << " items";
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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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int doppler;
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unsigned int indext = 0;
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float magt = 0.0;
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const lv_16sc_t *in = (const lv_16sc_t *)input_items[0]; //Get the input samples pointer
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int effective_fft_size = ( d_bit_transition_flag ? d_fft_size/2 : d_fft_size );
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//TODO: optimize the signal processing chain to not use gr_complex. This is a temporary solution
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volk_gnsssdr_16ic_convert_32fc(d_in_32fc,in,effective_fft_size);
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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_mag = 0.0;
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d_sample_counter += d_fft_size; // sample counter
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d_well_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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if (d_use_CFAR_algorithm_flag == true)
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{
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// 1- (optional) Compute the input signal power estimation
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volk_32fc_magnitude_squared_32f(d_magnitude, d_in_32fc, d_fft_size);
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volk_32f_accumulator_s32f(&d_input_power, d_magnitude, d_fft_size);
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d_input_power /= static_cast<float>(d_fft_size);
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}
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// 2- Doppler frequency search loop
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for (unsigned int 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<int>(d_doppler_max) + d_doppler_step * doppler_index;
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volk_32fc_x2_multiply_32fc(d_fft_if->get_inbuf(), d_in_32fc,
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d_grid_doppler_wipeoffs[doppler_index], 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, d_fft_size);
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// compute the inverse FFT
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d_ifft->execute();
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// Search maximum
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size_t offset = ( d_bit_transition_flag ? effective_fft_size : 0 );
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volk_32fc_magnitude_squared_32f(d_magnitude, d_ifft->get_outbuf() + offset, effective_fft_size);
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volk_32f_index_max_16u(&indext, d_magnitude, effective_fft_size);
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magt = d_magnitude[indext];
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if (d_use_CFAR_algorithm_flag == true)
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{
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// Normalize the maximum value to correct the scale factor introduced by FFTW
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magt = d_magnitude[indext] / (fft_normalization_factor * fft_normalization_factor);
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}
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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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if (d_use_CFAR_algorithm_flag == false)
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{
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// Search grid noise floor approximation for this doppler line
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volk_32f_accumulator_s32f(&d_input_power, d_magnitude, effective_fft_size);
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d_input_power = (d_input_power - d_mag) / (effective_fft_size - 1);
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}
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// In case that d_bit_transition_flag = true, we compare the potentially
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// new maximum test statistics (d_mag/d_input_power) with the value in
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// d_test_statistics. When the second dwell is being processed, the value
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// of d_mag/d_input_power could be lower than d_test_statistics (i.e,
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// the maximum test statistics in the previous dwell is greater than
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// current d_mag/d_input_power). Note that d_test_statistics is not
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// restarted between consecutive dwells in multidwell operation.
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if (d_test_statistics < (d_mag / d_input_power) || !d_bit_transition_flag)
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{
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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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// 5- Compute the test statistics and compare to the threshold
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d_test_statistics = d_mag / d_input_power;
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//std::cout<<"d_input_power="<<d_input_power<<" d_test_statistics="<<d_test_statistics<<" d_gnss_synchro->Acq_doppler_hz ="<<d_gnss_synchro->Acq_doppler_hz <<std::endl;
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}
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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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boost::filesystem::path p = d_dump_filename;
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filename << p.parent_path().string()
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<< boost::filesystem::path::preferred_separator
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<< p.stem().string()
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<< "_" << d_gnss_synchro->System
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<<"_" << d_gnss_synchro->Signal << "_sat_"
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<< d_gnss_synchro->PRN << "_doppler_"
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<< doppler
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<< p.extension().string();
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DLOG(INFO) << "Writing ACQ out to " << filename.str();
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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((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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if (!d_bit_transition_flag)
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{
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if (d_test_statistics > d_threshold)
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{
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d_state = 2; // Positive acquisition
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}
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else if (d_well_count == d_max_dwells)
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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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else
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{
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if (d_well_count == d_max_dwells) // d_max_dwells = 2
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{
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if (d_test_statistics > d_threshold)
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{
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d_state = 2; // Positive acquisition
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}
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else
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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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}
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consume_each(1);
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DLOG(INFO) << "Done. Consumed 1 item.";
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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 queue
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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;
|
|
DLOG(INFO) << "doppler " << d_gnss_synchro->Acq_doppler_hz;
|
|
DLOG(INFO) << "magnitude " << d_mag;
|
|
DLOG(INFO) << "input signal power " << d_input_power;
|
|
|
|
d_active = false;
|
|
d_state = 0;
|
|
|
|
d_sample_counter += d_fft_size * ninput_items[0]; // sample counter
|
|
consume_each(ninput_items[0]);
|
|
|
|
acquisition_message = 1;
|
|
this->message_port_pub(pmt::mp("events"), pmt::from_long(acquisition_message));
|
|
|
|
break;
|
|
}
|
|
|
|
case 3:
|
|
{
|
|
// 6.2- Declare negative acquisition using a message queue
|
|
DLOG(INFO) << "negative acquisition";
|
|
DLOG(INFO) << "satellite " << d_gnss_synchro->System << " " << d_gnss_synchro->PRN;
|
|
DLOG(INFO) << "sample_stamp " << d_sample_counter;
|
|
DLOG(INFO) << "test statistics value " << d_test_statistics;
|
|
DLOG(INFO) << "test statistics threshold " << d_threshold;
|
|
DLOG(INFO) << "code phase " << d_gnss_synchro->Acq_delay_samples;
|
|
DLOG(INFO) << "doppler " << d_gnss_synchro->Acq_doppler_hz;
|
|
DLOG(INFO) << "magnitude " << d_mag;
|
|
DLOG(INFO) << "input signal power " << d_input_power;
|
|
|
|
d_active = false;
|
|
d_state = 0;
|
|
|
|
d_sample_counter += d_fft_size * ninput_items[0]; // sample counter
|
|
consume_each(ninput_items[0]);
|
|
acquisition_message = 2;
|
|
this->message_port_pub(pmt::mp("events"), pmt::from_long(acquisition_message));
|
|
|
|
break;
|
|
}
|
|
}
|
|
|
|
return noutput_items;
|
|
}
|