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Faster resampler

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This commit is contained in:
Carles Fernandez 2015-05-05 13:00:24 +02:00
parent e354b1ce53
commit b4cfef1a44
2 changed files with 67 additions and 13 deletions
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30
src/algorithms/libs/gps_sdr_signal_processing.cc
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@ -34,11 +34,15 @@
#include <stdlib.h>
#include <cmath>
auto auxCeil = [](float x){ return static_cast<int>(static_cast<long>((x)+1)); };
void gps_l1_ca_code_gen_complex(std::complex<float>* _dest, signed int _prn, unsigned int _chip_shift)
{
bool G1[1023];
bool G2[1023];
const unsigned int _code_length = 1023;
bool G1[_code_length];
bool G2[_code_length];
bool G1_register[10], G2_register[10];
bool feedback1, feedback2;
bool aux;
@ -47,7 +51,7 @@ void gps_l1_ca_code_gen_complex(std::complex<float>* _dest, signed int _prn, uns
signed int prn_idx;
/* G2 Delays as defined in GPS-ISD-200D */
signed int delays[51] = {5 /*PRN1*/, 6, 7, 8, 17, 18, 139, 140, 141, 251, 252, 254 ,255, 256, 257, 258, 469, 470, 471, 472,
const signed int delays[51] = {5 /*PRN1*/, 6, 7, 8, 17, 18, 139, 140, 141, 251, 252, 254 ,255, 256, 257, 258, 469, 470, 471, 472,
473, 474, 509, 512, 513, 514, 515, 516, 859, 860, 861, 862 /*PRN32*/,
145 /*PRN120*/, 175, 52, 21, 237, 235, 886, 657, 634, 762,
355, 1012, 176, 603, 130, 359, 595, 68, 386 /*PRN138*/};
@ -73,7 +77,7 @@ void gps_l1_ca_code_gen_complex(std::complex<float>* _dest, signed int _prn, uns
}
/* Generate G1 & G2 Register */
for(lcv = 0; lcv < 1023; lcv++)
for(lcv = 0; lcv < _code_length; lcv++)
{
G1[lcv] = G1_register[0];
G2[lcv] = G2_register[0];
@ -92,14 +96,14 @@ void gps_l1_ca_code_gen_complex(std::complex<float>* _dest, signed int _prn, uns
}
/* Set the delay */
delay = 1023 - delays[prn_idx];
delay = _code_length - delays[prn_idx];
delay += _chip_shift;
delay %= 1023;
delay %= _code_length;
/* Generate PRN from G1 and G2 Registers */
for(lcv = 0; lcv < 1023; lcv++)
for(lcv = 0; lcv < _code_length; lcv++)
{
aux = G1[(lcv + _chip_shift) % 1023]^G2[delay];
aux = G1[(lcv + _chip_shift) % _code_length]^G2[delay];
if(aux == true)
{
_dest[lcv] = std::complex<float>(1, 0);
@ -109,7 +113,7 @@ void gps_l1_ca_code_gen_complex(std::complex<float>* _dest, signed int _prn, uns
_dest[lcv] = std::complex<float>(-1, 0);
}
delay++;
delay %= 1023;
delay %= _code_length;
}
}
@ -125,6 +129,7 @@ void gps_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int
signed int _samplesPerCode, _codeValueIndex;
float _ts;
float _tc;
float aux;
const signed int _codeFreqBasis = 1023000; //Hz
const signed int _codeLength = 1023;
@ -145,7 +150,9 @@ void gps_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int
// number of samples per millisecond (because one C/A code period is one
// millisecond).
_codeValueIndex = ceil((_ts * ((float)i + 1)) / _tc) - 1;
// _codeValueIndex = ceil((_ts * ((float)i + 1)) / _tc) - 1;
aux = (_ts * (i + 1)) / _tc;
_codeValueIndex = auxCeil( aux ) - 1;
//--- Make the digitized version of the C/A code -----------------------
// The "upsampled" code is made by selecting values form the CA code
@ -163,6 +170,3 @@ void gps_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int
}
}

50
src/tests/arithmetic/code_generation_test.cc
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@ -78,3 +78,53 @@ TEST(CodeGenGPSL1_Test, CodeGeneration)
}
delete _dest2; */
}
TEST(CodeGenGPSL1Sampled_Test, CodeGeneration)
{
signed int _prn = 1;
unsigned int _chip_shift = 4;
int _fs = 8000000;
const signed int _codeFreqBasis = 1023000; //Hz
const signed int _codeLength = 1023;
int _samplesPerCode = round(_fs / (_codeFreqBasis / _codeLength));
std::complex<float>* _dest = new std::complex<float>[_samplesPerCode];
int iterations = 10000;
struct timeval tv;
gettimeofday(&tv, NULL);
long long int begin = tv.tv_sec * 1000000 + tv.tv_usec;
for(int i = 0; i < iterations; i++)
{
gps_l1_ca_code_gen_complex_sampled( _dest, _prn, _fs, _chip_shift);
}
gettimeofday(&tv, NULL);
long long int end = tv.tv_sec * 1000000 + tv.tv_usec;
ASSERT_LE(0, end - begin);
std::cout << "Generation completed in " << (end - begin) << " microseconds" << std::endl;
delete[] _dest;
/* std::complex<float>* _dest2 = new std::complex<float>[_samplesPerCode];
gettimeofday(&tv, NULL);
long long int begin2 = tv.tv_sec * 1000000 + tv.tv_usec;
for(int i = 0; i < iterations; i++)
{
gps_l1_ca_code_gen_complex_sampled2( _dest2, _prn, _fs, _chip_shift);
}
gettimeofday(&tv, NULL);
long long int end2 = tv.tv_sec * 1000000 + tv.tv_usec;
std::cout << "Generation completed in " << (end2 - begin2) << " microseconds (New)" << std::endl;
for (int j=0; j<_samplesPerCode;j++)
{
if(_dest[j] != _dest2[j]) std::cout << "Error!" << std::endl;
}
delete[] _dest2; */
}