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Optimizations in PCPS Acquisition module:

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- Improved speed for normalization in the FFTW results
- Complex multiplications now use the SIMD instructions with VOLK library
- Carrier wipeoff now uses the GNU Radio fixed point NCO (gr_fxpt) 

git-svn-id: https://svn.code.sf.net/p/gnss-sdr/code/trunk@241 64b25241-fba3-4117-9849-534c7e92360d
This commit is contained in:
Javier Arribas
2012-09-04 14:29:07 +00:00
parent 03208cb76f
commit 0703dd2af3
2 changed files with 39 additions and 11 deletions
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25
src/algorithms/acquisition/gnuradio_blocks/pcps_acquisition_cc.cc
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@@ -38,6 +38,7 @@
#include <sstream> #include <sstream>
#include <glog/log_severity.h> #include <glog/log_severity.h>
#include <glog/logging.h> #include <glog/logging.h>
#include <volk/volk.h>
using google::LogMessage; using google::LogMessage;
@@ -124,7 +125,7 @@ void pcps_acquisition_cc::init()
for (unsigned int i = 0; i < d_fft_size; i++) for (unsigned int i = 0; i < d_fft_size; i++)
{ {
d_fft_codes[i] = std::complex<float>(conj(d_fft_if->get_outbuf()[i])); d_fft_codes[i] = std::complex<float>(conj(d_fft_if->get_outbuf()[i]));
d_fft_codes[i] = d_fft_codes[i] / (float)d_fft_size; //to correct the scale factor introduced by FFTW //d_fft_codes[i] = d_fft_codes[i] / (float)d_fft_size; //to correct the scale factor introduced by FFTW
} }
} }
@@ -176,6 +177,8 @@ int pcps_acquisition_cc::general_work(int noutput_items,
unsigned int i; unsigned int i;
float fft_normalization_factor;
DLOG(INFO) << "Channel: " << d_channel DLOG(INFO) << "Channel: " << d_channel
<< " , doing acquisition of satellite: " << d_gnss_synchro->System << " "<< d_gnss_synchro->PRN << " , doing acquisition of satellite: " << d_gnss_synchro->System << " "<< d_gnss_synchro->PRN
<< " ,sample stamp: " << d_sample_counter << ", threshold: " << " ,sample stamp: " << d_sample_counter << ", threshold: "
@@ -203,16 +206,23 @@ int pcps_acquisition_cc::general_work(int noutput_items,
//3- Perform the FFT-based circular convolution (parallel time search) //3- Perform the FFT-based circular convolution (parallel time search)
d_fft_if->execute(); d_fft_if->execute();
for (i = 0; i < d_fft_size; i++) // Using plain C++ operations
{ // for (i = 0; i < d_fft_size; i++)
d_ifft->get_inbuf()[i] = (d_fft_if->get_outbuf()[i] // {
* d_fft_codes[i]) / (float)d_fft_size; // d_ifft->get_inbuf()[i] = (d_fft_if->get_outbuf()[i]
} // * d_fft_codes[i]) / (float)d_fft_size;
// }
// 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);
d_ifft->execute(); d_ifft->execute();
// Search maximum // Search maximum
indext = 0; indext = 0;
magt = 0; magt = 0;
fft_normalization_factor=(float)d_fft_size*(float)d_fft_size;
for (i = 0; i < d_fft_size; i++) for (i = 0; i < d_fft_size; i++)
{ {
tmp_magt = std::norm(d_ifft->get_outbuf()[i]); tmp_magt = std::norm(d_ifft->get_outbuf()[i]);
@@ -223,6 +233,9 @@ int pcps_acquisition_cc::general_work(int noutput_items,
} }
} }
// Normalize the maximum value to correct the scale factor introduced by FFTW
magt=magt/(fft_normalization_factor*fft_normalization_factor);
// Record results to files // Record results to files
if (d_dump) if (d_dump)
{ {

25
src/algorithms/libs/gnss_signal_processing.cc
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@@ -32,17 +32,32 @@
*/ */
#include "gnss_signal_processing.h" #include "gnss_signal_processing.h"
#include <gr_fxpt.h>
void complex_exp_gen(std::complex<float>* _dest, double _f, double _fs, unsigned int _samps) void complex_exp_gen(std::complex<float>* _dest, double _f, double _fs, unsigned int _samps)
{ {
double phase = 0; //old
const double phase_step = (GPS_TWO_PI * _f) / _fs; //double phase = 0;
//const double phase_step = (GPS_TWO_PI * _f) / _fs;
//new Fixed Point NCO (faster)
int phase_i=0;
int phase_step_i;
float phase_step_f =(float)((GPS_TWO_PI * _f) / _fs);
phase_step_i=gr_fxpt::float_to_fixed(phase_step_f);
float sin_f,cos_f;
for(unsigned int i = 0; i < _samps; i++) for(unsigned int i = 0; i < _samps; i++)
{ {
_dest[i] = std::complex<float>(cos(phase), sin(phase)); //old
phase += phase_step; //_dest[i] = std::complex<float>(cos(phase), sin(phase));
//phase += phase_step;
//new Fixed Point NCO (faster)
gr_fxpt::sincos(phase_i,&sin_f,&cos_f);
_dest[i] = std::complex<float>(cos_f, sin_f);
phase_i += phase_step_i;
} }
} }