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

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/*!
* \file pcps_tong_acquisition_cc.h
* \brief This class implements a Parallel Code Phase Search Acquisition with
* Tong algorithm.
* \author Marc Molina, 2013. marc.molina.pena(at)gmail.com
*
* Acquisition strategy (Kaplan book + CFAR threshold).
* <ol>
* <li> Compute the input signal power estimation.
* <li> Doppler serial search loop.
* <li> Perform the FFT-based circular convolution (parallel time search).
* <li> Compute the tests statistics for all the cells.
* <li> Accumulate the grid of tests statistics with the previous grids.
* <li> Record the maximum peak and the associated synchronization parameters.
* <li> Compare the maximum averaged test statistics with a threshold.
* <li> If the test statistics exceeds the threshold, increment the Tong counter.
* <li> Otherwise, decrement the Tong counter.
* <li> If the Tong counter is equal to a given maximum value, declare positive
* <li> acquisition. If the Tong counter is equa to zero, declare negative
* <li> acquisition. Otherwise, process the next block.
* </ol>
*
* Kaplan book: D.Kaplan, J.Hegarty, "Understanding GPS. Principles
* and Applications", Artech House, 2006, pp 223-227
*
* -------------------------------------------------------------------------
*
* Copyright (C) 2010-2012 (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 <http://www.gnu.org/licenses/>.
*
* -------------------------------------------------------------------------
*/
#include "pcps_tong_acquisition_cc.h"
#include "gnss_signal_processing.h"
#include "control_message_factory.h"
#include <gnuradio/io_signature.h>
#include <sstream>
#include <glog/log_severity.h>
#include <glog/logging.h>
#include <volk/volk.h>
using google::LogMessage;
pcps_tong_acquisition_cc_sptr pcps_tong_make_acquisition_cc(
unsigned int sampled_ms, unsigned int doppler_max,
long freq, long fs_in, int samples_per_ms,
int samples_per_code, unsigned int tong_init_val,
unsigned int tong_max_val, gr::msg_queue::sptr queue,
bool dump, std::string dump_filename)
{
return pcps_tong_acquisition_cc_sptr(
new pcps_tong_acquisition_cc(sampled_ms, doppler_max, freq, fs_in, samples_per_ms, samples_per_code,
tong_init_val, tong_max_val, queue, dump, dump_filename));
}
pcps_tong_acquisition_cc::pcps_tong_acquisition_cc(
unsigned int sampled_ms, unsigned int doppler_max,
long freq, long fs_in, int samples_per_ms,
int samples_per_code, unsigned int tong_init_val,
unsigned int tong_max_val, gr::msg_queue::sptr queue,
bool dump, std::string dump_filename) :
gr::block("pcps_tong_acquisition_cc",
gr::io_signature::make(1, 1, sizeof(gr_complex) * sampled_ms * samples_per_ms),
gr::io_signature::make(0, 0, sizeof(gr_complex) * sampled_ms * samples_per_ms))
{
d_sample_counter = 0; // SAMPLE COUNTER
d_active = false;
d_state = 0;
d_queue = queue;
d_freq = freq;
d_fs_in = fs_in;
d_samples_per_ms = samples_per_ms;
d_samples_per_code = samples_per_code;
d_sampled_ms = sampled_ms;
d_well_count = 0;
d_tong_max_val = tong_max_val;
d_tong_init_val = tong_init_val;
d_tong_count = d_tong_init_val;
d_doppler_max = doppler_max;
d_fft_size = d_sampled_ms * d_samples_per_ms;
d_mag = 0;
d_input_power = 0.0;
d_num_doppler_bins = 0;
//todo: do something if posix_memalign fails
if (posix_memalign((void**)&d_fft_codes, 16, d_fft_size * sizeof(gr_complex)) == 0){};
if (posix_memalign((void**)&d_magnitude, 16, d_fft_size * sizeof(gr_complex)) == 0){};
// Direct FFT
d_fft_if = new gr::fft::fft_complex(d_fft_size, true);
// Inverse FFT
d_ifft = new gr::fft::fft_complex(d_fft_size, false);
// For dumping samples into a file
d_dump = dump;
d_dump_filename = dump_filename;
}
pcps_tong_acquisition_cc::~pcps_tong_acquisition_cc()
{
for (unsigned int doppler_index = 0; doppler_index < d_num_doppler_bins; doppler_index++)
{
free(d_grid_doppler_wipeoffs[doppler_index]);
free(d_grid_data[doppler_index]);
}
if (d_num_doppler_bins > 0)
{
delete[] d_grid_doppler_wipeoffs;
delete[] d_grid_data;
}
free(d_fft_codes);
free(d_magnitude);
delete d_ifft;
delete d_fft_if;
if (d_dump)
{
d_dump_file.close();
}
}
void pcps_tong_acquisition_cc::set_local_code(std::complex<float> * code)
{
memcpy(d_fft_if->get_inbuf(), code, sizeof(gr_complex)*d_fft_size);
d_fft_if->execute(); // We need the FFT of local code
//Conjugate the local code
if (is_unaligned())
{
volk_32fc_conjugate_32fc_u(d_fft_codes,d_fft_if->get_outbuf(),d_fft_size);
}
else
{
volk_32fc_conjugate_32fc_a(d_fft_codes,d_fft_if->get_outbuf(),d_fft_size);
}
}
void pcps_tong_acquisition_cc::init()
{
d_gnss_synchro->Acq_delay_samples = 0.0;
d_gnss_synchro->Acq_doppler_hz = 0.0;
d_gnss_synchro->Acq_samplestamp_samples = 0;
d_mag = 0.0;
d_input_power = 0.0;
// Create the carrier Doppler wipeoff signals
d_num_doppler_bins = 0;//floor(2*std::abs((int)d_doppler_max)/d_doppler_step);
for (int doppler = (int)(-d_doppler_max); doppler <= (int)d_doppler_max; doppler += d_doppler_step)
{
d_num_doppler_bins++;
}
d_grid_doppler_wipeoffs = new gr_complex*[d_num_doppler_bins];
d_grid_data = new float*[d_num_doppler_bins];
for (unsigned int doppler_index=0;doppler_index<d_num_doppler_bins;doppler_index++)
{
if (posix_memalign((void**)&(d_grid_doppler_wipeoffs[doppler_index]), 16,
d_fft_size * sizeof(gr_complex)) == 0){};
int doppler=-(int)d_doppler_max+d_doppler_step*doppler_index;
complex_exp_gen_conj(d_grid_doppler_wipeoffs[doppler_index],
d_freq + doppler, d_fs_in, d_fft_size);
if (posix_memalign((void**)&(d_grid_data[doppler_index]), 16,
d_fft_size * sizeof(float)) == 0){};
for (unsigned int i = 0; i < d_fft_size; i++)
{
d_grid_data[doppler_index][i] = 0;
}
}
}
int pcps_tong_acquisition_cc::general_work(int noutput_items,
gr_vector_int &ninput_items, gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
int acquisition_message = -1; //0=STOP_CHANNEL 1=ACQ_SUCCEES 2=ACQ_FAIL
switch (d_state)
{
case 0:
{
if (d_active)
{
//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 = 0;
d_well_count = 0;
d_tong_count = d_tong_init_val;
d_mag = 0.0;
d_input_power = 0.0;
d_test_statistics = 0.0;
for (unsigned int doppler_index=0;doppler_index<d_num_doppler_bins;doppler_index++)
{
for (unsigned int i = 0; i < d_fft_size; i++)
{
d_grid_data[doppler_index][i] = 0;
}
}
d_state = 1;
}
d_sample_counter += d_fft_size * ninput_items[0]; // sample counter
consume_each(ninput_items[0]);
break;
}
case 1:
{
// initialize acquisition algorithm
int doppler;
unsigned int indext = 0;
float magt = 0.0;
const gr_complex *in = (const gr_complex *)input_items[0]; //Get the input samples pointer
float fft_normalization_factor = (float)d_fft_size * (float)d_fft_size;
d_input_power = 0.0;
d_mag = 0.0;
d_sample_counter += d_fft_size; // sample counter
d_well_count++;
DLOG(INFO) << "Channel: " << d_channel
<< " , doing acquisition of satellite: " << d_gnss_synchro->System << " "<< d_gnss_synchro->PRN
<< " ,sample stamp: " << d_sample_counter << ", threshold: "
<< d_threshold << ", doppler_max: " << d_doppler_max
<< ", doppler_step: " << d_doppler_step;
// 1- Compute the input signal power estimation
volk_32fc_magnitude_squared_32f_a(d_magnitude, in, d_fft_size);
volk_32f_accumulator_s32f_a(&d_input_power, d_magnitude, d_fft_size);
d_input_power /= (float)d_fft_size;
// 2- Doppler frequency search loop
for (unsigned int doppler_index=0;doppler_index<d_num_doppler_bins;doppler_index++)
{
// doppler search steps
doppler=-(int)d_doppler_max+d_doppler_step*doppler_index;
volk_32fc_x2_multiply_32fc_a(d_fft_if->get_inbuf(), in,
d_grid_doppler_wipeoffs[doppler_index], d_fft_size);
// 3- 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_a(d_ifft->get_inbuf(),
d_fft_if->get_outbuf(), d_fft_codes, d_fft_size);
// compute the inverse FFT
d_ifft->execute();
// Search maximum
volk_32fc_magnitude_squared_32f_a(d_magnitude, d_ifft->get_outbuf(), d_fft_size);
volk_32f_s32f_multiply_32f_a(d_magnitude, d_magnitude,
1/(fft_normalization_factor*fft_normalization_factor*d_input_power),
d_fft_size);
volk_32f_x2_add_32f_a(d_grid_data[doppler_index], d_magnitude, d_grid_data[doppler_index], d_fft_size);
volk_32f_index_max_16u_a(&indext, d_grid_data[doppler_index], d_fft_size);
// Normalize the maximum value to correct the scale factor introduced by FFTW
magt = d_grid_data[doppler_index][indext];
// 4- record the maximum peak and the associated synchronization parameters
if (d_mag < magt)
{
d_mag = magt;
d_gnss_synchro->Acq_delay_samples = (double)(indext % d_samples_per_code);
d_gnss_synchro->Acq_doppler_hz = (double)doppler;
d_gnss_synchro->Acq_samplestamp_samples = d_sample_counter;
}
// Record results to file if required
if (d_dump)
{
std::stringstream filename;
std::streamsize n = 2 * sizeof(float) * (d_fft_size); // complex file write
filename.str("");
filename << "../data/test_statistics_" << d_gnss_synchro->System
<<"_" << d_gnss_synchro->Signal << "_sat_"
<< d_gnss_synchro->PRN << "_doppler_" << doppler << ".dat";
d_dump_file.open(filename.str().c_str(), std::ios::out | std::ios::binary);
d_dump_file.write((char*)d_ifft->get_outbuf(), n); //write directly |abs(x)|^2 in this Doppler bin?
d_dump_file.close();
}
}
// 5- Compute the test statistics and compare to the threshold
//d_test_statistics = 2 * d_fft_size * d_mag / d_input_power;
d_test_statistics = d_mag;
if (d_test_statistics > d_threshold*d_well_count)
{
d_tong_count++;
if (d_tong_count == d_tong_max_val)
{
d_state = 2; // Positive acquisition
}
}
else
{
d_tong_count--;
if (d_tong_count == 0)
{
d_state = 3; // Negative acquisition
}
}
consume_each(1);
break;
}
case 2:
{
// 6.1- Declare positive acquisition using a message queue
DLOG(INFO) << "positive 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 = 1;
d_channel_internal_queue->push(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;
d_channel_internal_queue->push(acquisition_message);
break;
}
}
return 0;
}
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