[hamradio-commits] [gnss-sdr] 19/251: Faster resampler
Carles Fernandez
carles_fernandez-guest at moszumanska.debian.org
Wed Sep 2 00:22:32 UTC 2015
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carles_fernandez-guest pushed a commit to branch master
in repository gnss-sdr.
commit b4cfef1a449c5de56d3c0f49389a3cfd1d640864
Author: Carles Fernandez <carles.fernandez at gmail.com>
Date: Tue May 5 13:00:24 2015 +0200
Faster resampler
---
src/algorithms/libs/gps_sdr_signal_processing.cc | 30 ++++++++------
src/tests/arithmetic/code_generation_test.cc | 50 ++++++++++++++++++++++++
2 files changed, 67 insertions(+), 13 deletions(-)
diff --git a/src/algorithms/libs/gps_sdr_signal_processing.cc b/src/algorithms/libs/gps_sdr_signal_processing.cc
index 5ac0c19..714c2dc 100644
--- a/src/algorithms/libs/gps_sdr_signal_processing.cc
+++ b/src/algorithms/libs/gps_sdr_signal_processing.cc
@@ -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
}
}
-
-
-
diff --git a/src/tests/arithmetic/code_generation_test.cc b/src/tests/arithmetic/code_generation_test.cc
index 0813cad..aea2f50 100644
--- a/src/tests/arithmetic/code_generation_test.cc
+++ b/src/tests/arithmetic/code_generation_test.cc
@@ -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; */
+}
--
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