mirror of
https://github.com/gnss-sdr/gnss-sdr
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283 lines
7.5 KiB
C++
283 lines
7.5 KiB
C++
/*!
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* \file gps_l1_ca_pcps_acquisition_fpga.cc
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* \brief Adapts a PCPS acquisition block to an FPGA Acquisition Interface for
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* GPS L1 C/A signals. This file is based on the file gps_l1_ca_pcps_acquisition.cc
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* \authors <ul>
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* <li> Marc Majoral, 2017. mmajoral(at)cttc.cat
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* </ul>
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*
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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2017 (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 "gps_l1_ca_pcps_acquisition_fpga.h"
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#include <boost/math/distributions/exponential.hpp>
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#include <glog/logging.h>
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#include "gps_sdr_signal_processing.h"
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#include "GPS_L1_CA.h"
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#include "configuration_interface.h"
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using google::LogMessage;
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GpsL1CaPcpsAcquisitionFpga::GpsL1CaPcpsAcquisitionFpga(
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ConfigurationInterface* configuration, std::string role,
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unsigned int in_streams, unsigned int out_streams) :
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role_(role), in_streams_(in_streams), out_streams_(out_streams)
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{
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configuration_ = configuration;
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std::string default_item_type = "cshort";
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std::string default_dump_filename = "./data/acquisition.dat";
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DLOG(INFO) << "role " << role;
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item_type_ = configuration_->property(role + ".item_type", default_item_type);
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fs_in_ = configuration_->property("GNSS-SDR.internal_fs_hz", 2048000);
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if_ = configuration_->property(role + ".if", 0);
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dump_ = configuration_->property(role + ".dump", false);
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doppler_max_ = configuration_->property(role + ".doppler_max", 5000);
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sampled_ms_ = configuration_->property(role + ".coherent_integration_time_ms", 1);
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// note : the FPGA is implemented according to bit transition flag = 0. Setting bit transition flag to 1 has no effect.
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bit_transition_flag_ = configuration_->property(role + ".bit_transition_flag", false);
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// note : the FPGA is implemented according to use_CFAR_algorithm = 0. Setting use_CFAR_algorithm to 1 has no effect.
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use_CFAR_algorithm_flag_=configuration_->property(role + ".use_CFAR_algorithm", false);
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max_dwells_ = configuration_->property(role + ".max_dwells", 1);
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dump_filename_ = configuration_->property(role + ".dump_filename", default_dump_filename);
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//--- Find number of samples per spreading code -------------------------
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code_length_ = round(fs_in_ / (GPS_L1_CA_CODE_RATE_HZ / GPS_L1_CA_CODE_LENGTH_CHIPS));
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// code length has the same value as d_fft_size
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float nbits;
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nbits = ceilf(log2f(code_length_));
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nsamples_total_ = pow(2,nbits);
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//vector_length_ = code_length_ * sampled_ms_;
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vector_length_ = nsamples_total_ * sampled_ms_;
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if( bit_transition_flag_ )
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{
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vector_length_ *= 2;
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}
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code_ = new gr_complex[vector_length_];
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if (item_type_.compare("cshort") == 0 )
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{
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item_size_ = sizeof(lv_16sc_t);
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gps_acquisition_fpga_sc_ = gps_pcps_make_acquisition_fpga_sc(sampled_ms_, max_dwells_,
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doppler_max_, if_, fs_in_, code_length_, code_length_, vector_length_,
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bit_transition_flag_, use_CFAR_algorithm_flag_, dump_, dump_filename_);
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DLOG(INFO) << "acquisition(" << gps_acquisition_fpga_sc_->unique_id() << ")";
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}
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else{
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LOG(FATAL) << item_type_ << " FPGA only accepts chsort";
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}
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channel_ = 0;
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threshold_ = 0.0;
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doppler_step_ = 0;
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gnss_synchro_ = 0;
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}
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GpsL1CaPcpsAcquisitionFpga::~GpsL1CaPcpsAcquisitionFpga()
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{
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delete[] code_;
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}
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void GpsL1CaPcpsAcquisitionFpga::set_channel(unsigned int channel)
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{
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channel_ = channel;
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gps_acquisition_fpga_sc_->set_channel(channel_);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_threshold(float threshold)
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{
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float pfa = configuration_->property(role_ + ".pfa", 0.0);
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if(pfa == 0.0)
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{
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threshold_ = threshold;
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}
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else
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{
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threshold_ = calculate_threshold(pfa);
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}
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DLOG(INFO) << "Channel " << channel_ << " Threshold = " << threshold_;
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gps_acquisition_fpga_sc_->set_threshold(threshold_);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_doppler_max(unsigned int doppler_max)
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{
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doppler_max_ = doppler_max;
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gps_acquisition_fpga_sc_->set_doppler_max(doppler_max_);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_doppler_step(unsigned int doppler_step)
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{
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doppler_step_ = doppler_step;
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gps_acquisition_fpga_sc_->set_doppler_step(doppler_step_);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_gnss_synchro(Gnss_Synchro* gnss_synchro)
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{
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gnss_synchro_ = gnss_synchro;
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gps_acquisition_fpga_sc_->set_gnss_synchro(gnss_synchro_);
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}
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signed int GpsL1CaPcpsAcquisitionFpga::mag()
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{
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return gps_acquisition_fpga_sc_->mag();
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}
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void GpsL1CaPcpsAcquisitionFpga::init()
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{
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gps_acquisition_fpga_sc_->init();
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set_local_code();
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}
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void GpsL1CaPcpsAcquisitionFpga::set_local_code()
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{
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std::complex<float>* code = new std::complex<float>[vector_length_];
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//init to zeros for the zero padding of the fft
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for (uint s=0;s<vector_length_;s++)
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{
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code[s] = std::complex<float>(0, 0);
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}
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unsigned long long interpolated_sampling_frequency; // warning: we need a long long to do this conversion to avoid running out of bits
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gps_l1_ca_code_gen_complex_sampled(code, gnss_synchro_->PRN, fs_in_ , 0);
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for (unsigned int i = 0; i < sampled_ms_; i++)
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{
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memcpy(&(code_[i*vector_length_]), code, sizeof(gr_complex)*vector_length_);
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}
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gps_acquisition_fpga_sc_->set_local_code(code_);
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delete[] code;
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}
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void GpsL1CaPcpsAcquisitionFpga::reset()
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{
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gps_acquisition_fpga_sc_->set_active(true);
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}
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void GpsL1CaPcpsAcquisitionFpga::set_state(int state)
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{
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gps_acquisition_fpga_sc_->set_state(state);
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}
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float GpsL1CaPcpsAcquisitionFpga::calculate_threshold(float pfa)
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{
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//Calculate the threshold
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unsigned int frequency_bins = 0;
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for (int doppler = (int)(-doppler_max_); doppler <= (int)doppler_max_; doppler += doppler_step_)
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{
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frequency_bins++;
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}
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DLOG(INFO) << "Channel " << channel_ << " Pfa = " << pfa;
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unsigned int ncells = vector_length_ * frequency_bins;
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double exponent = 1 / static_cast<double>(ncells);
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double val = pow(1.0 - pfa, exponent);
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double lambda = double(vector_length_);
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boost::math::exponential_distribution<double> mydist (lambda);
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float threshold = (float)quantile(mydist,val);
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return threshold;
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}
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void GpsL1CaPcpsAcquisitionFpga::connect(gr::top_block_sptr top_block)
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{
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//nothing to connect
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}
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void GpsL1CaPcpsAcquisitionFpga::disconnect(gr::top_block_sptr top_block)
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{
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//nothing to disconnect
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}
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gr::basic_block_sptr GpsL1CaPcpsAcquisitionFpga::get_left_block()
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{
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return gps_acquisition_fpga_sc_;
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}
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gr::basic_block_sptr GpsL1CaPcpsAcquisitionFpga::get_right_block()
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{
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return gps_acquisition_fpga_sc_;
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}
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