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Enable second refinement stage in a thinner grid for coherent and/or non-coherent acquisitions

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This commit is contained in:
Carles Fernandez 2018-07-13 11:50:31 +02:00
parent b779f5cb3d
commit 92a6676b9e
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GPG Key ID: 4C583C52B0C3877D
3 changed files with 59 additions and 61 deletions
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87
src/algorithms/acquisition/gnuradio_blocks/pcps_acquisition.cc
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@ -460,7 +460,7 @@ void pcps_acquisition::dump_results(int effective_fft_size)
} }
float pcps_acquisition::max_to_input_power_statistic(uint32_t& indext, int& doppler, float input_power) float pcps_acquisition::max_to_input_power_statistic(uint32_t& indext, int& doppler, float input_power, unsigned int num_doppler_bins, int doppler_max, int doppler_step)
{ {
float grid_maximum = 0.0; float grid_maximum = 0.0;
unsigned int index_doppler = 0; unsigned int index_doppler = 0;
@ -469,7 +469,7 @@ float pcps_acquisition::max_to_input_power_statistic(uint32_t& indext, int& dopp
float fft_normalization_factor = static_cast<float>(d_fft_size) * static_cast<float>(d_fft_size); float fft_normalization_factor = static_cast<float>(d_fft_size) * static_cast<float>(d_fft_size);
// Find the correlation peak and the carrier frequency // Find the correlation peak and the carrier frequency
for (unsigned int i = 0; i < d_num_doppler_bins; i++) for (unsigned int i = 0; i < num_doppler_bins; i++)
{ {
volk_gnsssdr_32f_index_max_32u(&tmp_intex_t, d_magnitude_grid[i], d_fft_size); volk_gnsssdr_32f_index_max_32u(&tmp_intex_t, d_magnitude_grid[i], d_fft_size);
if (d_magnitude_grid[i][tmp_intex_t] > grid_maximum) if (d_magnitude_grid[i][tmp_intex_t] > grid_maximum)
@ -480,14 +480,21 @@ float pcps_acquisition::max_to_input_power_statistic(uint32_t& indext, int& dopp
} }
} }
indext = index_time; indext = index_time;
doppler = -static_cast<int>(acq_parameters.doppler_max) + d_doppler_step * static_cast<int>(index_doppler); if (!d_step_two)
{
doppler = -static_cast<int>(doppler_max) + doppler_step * static_cast<int>(index_doppler);
}
else
{
doppler = static_cast<int>(d_doppler_center_step_two + (index_doppler - (acq_parameters.num_doppler_bins_step2 / 2.0) * acq_parameters.doppler_step2));
}
float magt = grid_maximum / (fft_normalization_factor * fft_normalization_factor); float magt = grid_maximum / (fft_normalization_factor * fft_normalization_factor);
return magt / input_power; return magt / input_power;
} }
float pcps_acquisition::first_vs_second_peak_statistic(uint32_t& indext, int& doppler) float pcps_acquisition::first_vs_second_peak_statistic(uint32_t& indext, int& doppler, unsigned int num_doppler_bins, int doppler_max, int doppler_step)
{ {
// Look for correlation peaks in the results // Look for correlation peaks in the results
// Find the highest peak and compare it to the second highest peak // Find the highest peak and compare it to the second highest peak
@ -499,7 +506,7 @@ float pcps_acquisition::first_vs_second_peak_statistic(uint32_t& indext, int& do
uint32_t index_time = 0; uint32_t index_time = 0;
// Find the correlation peak and the carrier frequency // Find the correlation peak and the carrier frequency
for (unsigned int i = 0; i < d_num_doppler_bins; i++) for (unsigned int i = 0; i < num_doppler_bins; i++)
{ {
volk_gnsssdr_32f_index_max_32u(&tmp_intex_t, d_magnitude_grid[i], d_fft_size); volk_gnsssdr_32f_index_max_32u(&tmp_intex_t, d_magnitude_grid[i], d_fft_size);
if (d_magnitude_grid[i][tmp_intex_t] > firstPeak) if (d_magnitude_grid[i][tmp_intex_t] > firstPeak)
@ -510,7 +517,15 @@ float pcps_acquisition::first_vs_second_peak_statistic(uint32_t& indext, int& do
} }
} }
indext = index_time; indext = index_time;
doppler = -static_cast<int>(acq_parameters.doppler_max) + d_doppler_step * static_cast<int>(index_doppler);
if (!d_step_two)
{
doppler = -static_cast<int>(doppler_max) + doppler_step * static_cast<int>(index_doppler);
}
else
{
doppler = static_cast<int>(d_doppler_center_step_two + (index_doppler - (acq_parameters.num_doppler_bins_step2 / 2.0) * acq_parameters.doppler_step2));
}
// Find 1 chip wide code phase exclude range around the peak // Find 1 chip wide code phase exclude range around the peak
int32_t excludeRangeIndex1 = index_time - d_samplesPerChip; int32_t excludeRangeIndex1 = index_time - d_samplesPerChip;
@ -629,11 +644,11 @@ void pcps_acquisition::acquisition_core(unsigned long int samp_count)
// Compute the test statistic // Compute the test statistic
if (d_use_CFAR_algorithm_flag) if (d_use_CFAR_algorithm_flag)
{ {
d_test_statistics = max_to_input_power_statistic(indext, doppler, d_input_power); d_test_statistics = max_to_input_power_statistic(indext, doppler, d_input_power, d_num_doppler_bins, acq_parameters.doppler_max, d_doppler_step);
} }
else else
{ {
d_test_statistics = first_vs_second_peak_statistic(indext, doppler); d_test_statistics = first_vs_second_peak_statistic(indext, doppler, d_num_doppler_bins, acq_parameters.doppler_max, d_doppler_step);
} }
d_gnss_synchro->Acq_delay_samples = static_cast<double>(indext % acq_parameters.samples_per_code); d_gnss_synchro->Acq_delay_samples = static_cast<double>(indext % acq_parameters.samples_per_code);
d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler); d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler);
@ -643,9 +658,6 @@ void pcps_acquisition::acquisition_core(unsigned long int samp_count)
{ {
for (unsigned int doppler_index = 0; doppler_index < acq_parameters.num_doppler_bins_step2; doppler_index++) for (unsigned int doppler_index = 0; doppler_index < acq_parameters.num_doppler_bins_step2; doppler_index++)
{ {
// doppler search steps
float doppler = d_doppler_center_step_two + (static_cast<float>(doppler_index) - static_cast<float>(acq_parameters.num_doppler_bins_step2) / 2.0) * acq_parameters.doppler_step2;
volk_32fc_x2_multiply_32fc(d_fft_if->get_inbuf(), in, d_grid_doppler_wipeoffs_step_two[doppler_index], d_fft_size); volk_32fc_x2_multiply_32fc(d_fft_if->get_inbuf(), in, d_grid_doppler_wipeoffs_step_two[doppler_index], d_fft_size);
// 3- Perform the FFT-based convolution (parallel time search) // 3- Perform the FFT-based convolution (parallel time search)
@ -659,54 +671,29 @@ void pcps_acquisition::acquisition_core(unsigned long int samp_count)
// compute the inverse FFT // compute the inverse FFT
d_ifft->execute(); d_ifft->execute();
// Search maximum
size_t offset = (acq_parameters.bit_transition_flag ? effective_fft_size : 0); size_t offset = (acq_parameters.bit_transition_flag ? effective_fft_size : 0);
volk_32fc_magnitude_squared_32f(d_magnitude, d_ifft->get_outbuf() + offset, effective_fft_size); if (d_num_noncoherent_integrations_counter == 1)
volk_gnsssdr_32f_index_max_32u(&indext, d_magnitude, effective_fft_size); {
magt = d_magnitude[indext]; volk_32fc_magnitude_squared_32f(d_magnitude_grid[doppler_index], d_ifft->get_outbuf() + offset, effective_fft_size);
}
else
{
volk_32fc_magnitude_squared_32f(d_tmp_buffer, d_ifft->get_outbuf() + offset, effective_fft_size);
volk_32f_x2_add_32f(d_magnitude_grid[doppler_index], d_magnitude_grid[doppler_index], d_tmp_buffer, effective_fft_size);
}
}
// Compute the test statistic
if (d_use_CFAR_algorithm_flag) if (d_use_CFAR_algorithm_flag)
{ {
// Normalize the maximum value to correct the scale factor introduced by FFTW d_test_statistics = max_to_input_power_statistic(indext, doppler, d_input_power, acq_parameters.num_doppler_bins_step2, static_cast<int>(d_doppler_center_step_two - (static_cast<float>(acq_parameters.num_doppler_bins_step2) / 2.0) * acq_parameters.doppler_step2), acq_parameters.doppler_step2);
magt = d_magnitude[indext] / (fft_normalization_factor * fft_normalization_factor);
} }
// 4- record the maximum peak and the associated synchronization parameters else
if (d_mag < magt)
{ {
d_mag = magt; d_test_statistics = first_vs_second_peak_statistic(indext, doppler, acq_parameters.num_doppler_bins_step2, static_cast<int>(d_doppler_center_step_two - (static_cast<float>(acq_parameters.num_doppler_bins_step2) / 2.0) * acq_parameters.doppler_step2), acq_parameters.doppler_step2);
if (!d_use_CFAR_algorithm_flag)
{
// Search grid noise floor approximation for this doppler line
volk_32f_accumulator_s32f(&d_input_power, d_magnitude, effective_fft_size);
d_input_power = (d_input_power - d_mag) / (effective_fft_size - 1);
} }
// In case that acq_parameters.bit_transition_flag = true, we compare the potentially
// new maximum test statistics (d_mag/d_input_power) with the value in
// d_test_statistics. When the second dwell is being processed, the value
// of d_mag/d_input_power could be lower than d_test_statistics (i.e,
// the maximum test statistics in the previous dwell is greater than
// current d_mag/d_input_power). Note that d_test_statistics is not
// restarted between consecutive dwells in multidwell operation.
if (d_test_statistics < (d_mag / d_input_power) or !acq_parameters.bit_transition_flag)
{
d_gnss_synchro->Acq_delay_samples = static_cast<double>(indext % acq_parameters.samples_per_code); d_gnss_synchro->Acq_delay_samples = static_cast<double>(indext % acq_parameters.samples_per_code);
d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler); d_gnss_synchro->Acq_doppler_hz = static_cast<double>(doppler);
d_gnss_synchro->Acq_samplestamp_samples = samp_count; d_gnss_synchro->Acq_samplestamp_samples = samp_count;
// 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 / d_input_power;
}
}
// Record results to file if required
if (acq_parameters.dump and d_channel == d_dump_channel)
{
memcpy(grid_.colptr(doppler_index), d_magnitude, sizeof(float) * effective_fft_size);
}
}
} }
lk.lock(); lk.lock();

4
src/algorithms/acquisition/gnuradio_blocks/pcps_acquisition.h
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@ -95,8 +95,8 @@ private:
void dump_results(int effective_fft_size); void dump_results(int effective_fft_size);
float first_vs_second_peak_statistic(uint32_t& indext, int& doppler); float first_vs_second_peak_statistic(uint32_t& indext, int& doppler, unsigned int num_doppler_bins, int doppler_max, int doppler_step);
float max_to_input_power_statistic(uint32_t& indext, int& doppler, float input_power); float max_to_input_power_statistic(uint32_t& indext, int& doppler, float input_power, unsigned int num_doppler_bins, int doppler_max, int doppler_step);
Acq_Conf acq_parameters; Acq_Conf acq_parameters;
bool d_active; bool d_active;

21
src/tests/unit-tests/signal-processing-blocks/acquisition/acq_performance_test.cc
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@ -54,9 +54,12 @@ DEFINE_string(acq_test_implementation, std::string("GPS_L1_CA_PCPS_Acquisition")
DEFINE_int32(acq_test_doppler_max, 5000, "Maximum Doppler, in Hz"); DEFINE_int32(acq_test_doppler_max, 5000, "Maximum Doppler, in Hz");
DEFINE_int32(acq_test_doppler_step, 125, "Doppler step, in Hz."); DEFINE_int32(acq_test_doppler_step, 125, "Doppler step, in Hz.");
DEFINE_int32(acq_test_coherent_time_ms, 1, "Acquisition coherent time, in ms"); DEFINE_int32(acq_test_coherent_time_ms, 1, "Acquisition coherent time, in ms");
DEFINE_int32(acq_test_max_dwells, 1, "Number of non-coherent integrations"); DEFINE_int32(acq_test_max_dwells, 1, "Number of non-coherent integrations.");
DEFINE_bool(acq_test_use_CFAR_algorithm, true, "Use CFAR algorithm"); DEFINE_bool(acq_test_use_CFAR_algorithm, true, "Use CFAR algorithm.");
DEFINE_bool(acq_test_bit_transition_flag, false, "Bit transition flag"); DEFINE_bool(acq_test_bit_transition_flag, false, "Bit transition flag.");
DEFINE_bool(acq_test_make_two_steps, false, "Perform second step in a thinner grid.");
DEFINE_int32(acq_test_second_nbins, 4, "If --acq_test_make_two_steps is set to true, this parameter sets the number of bins done in the acquisition refinement stage.");
DEFINE_int32(acq_test_second_doppler_step, 10, "If --acq_test_make_two_steps is set to true, this parameter sets the Doppler step applied in the acquisition refinement stage, in Hz.");
DEFINE_int32(acq_test_signal_duration_s, 2, "Generated signal duration, in s"); DEFINE_int32(acq_test_signal_duration_s, 2, "Generated signal duration, in s");
DEFINE_int32(acq_test_num_meas, 0, "Number of measurements per run. 0 means the complete file."); DEFINE_int32(acq_test_num_meas, 0, "Number of measurements per run. 0 means the complete file.");
@ -501,9 +504,17 @@ int AcquisitionPerformanceTest::configure_receiver(double cn0, float pfa, unsign
config->set_property("Acquisition.repeat_satellite", "true"); config->set_property("Acquisition.repeat_satellite", "true");
config->set_property("Acquisition.blocking", "true"); config->set_property("Acquisition.blocking", "true");
if (FLAGS_acq_test_make_two_steps)
{
config->set_property("Acquisition.make_two_steps", "true");
config->set_property("Acquisition.second_nbins", std::to_string(FLAGS_acq_test_second_nbins));
config->set_property("Acquisition.second_doppler_step", std::to_string(FLAGS_acq_test_second_doppler_step));
}
else
{
config->set_property("Acquisition.make_two_steps", "false"); config->set_property("Acquisition.make_two_steps", "false");
config->set_property("Acquisition.second_nbins", std::to_string(4)); }
config->set_property("Acquisition.second_doppler_step", std::to_string(125));
config->set_property("Acquisition.dump", "true"); config->set_property("Acquisition.dump", "true");
std::string dump_file = path_str + std::string("/acquisition_") + std::to_string(cn0) + "_" + std::to_string(iter) + "_" + std::to_string(pfa); std::string dump_file = path_str + std::string("/acquisition_") + std::to_string(cn0) + "_" + std::to_string(iter) + "_" + std::to_string(pfa);