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Bugfix for Spirent PRS code generator

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Not sure about this one. From my understanding of the Spirent knowledge
base description of the way in which the PRS code is generated, the
first PRS code chip for PRN 1 should be the same as the second p-code
chip for PRN 1, but it appears that in fact what is generated is the
last chip of the week. In other words the offset is -1 not +1.

With this modification I can successfully process E1 PRS data for both
even and odd numbered PRNs
This commit is contained in:
Cillian O'Driscoll
2015-11-10 21:01:13 +00:00
parent 1abd31d764
commit 9f40189f39
2 changed files with 57 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
src/algorithms/libs/spirent_prs_code_generator.cc
View File

@@ -30,6 +30,7 @@
*/
#include "spirent_prs_code_generator.h"
#include "GPS_P_CODE.h"
SpirentPrsCodeGenerator::SpirentPrsCodeGenerator( int sv, bool is_e1 )
: d_sv( sv ),
@@ -50,7 +51,17 @@ bool SpirentPrsCodeGenerator::get_chips( uint64_t first_chip_index,
// For E1 we have a downsample factor of 4, while the factor is 2
// for E6. The offset is chosen by spirent as 0 for even PRNS and 1
// for odd PRNS
d_code_gen.get_chips( d_sv, d_downsample_factor*first_chip_index + d_offset,
uint64_t first_p_chip_index = d_downsample_factor*first_chip_index;
if( first_p_chip_index < d_offset )
{
first_p_chip_index = first_p_chip_index + get_code_length() - d_offset;
}
else
{
first_p_chip_index = first_p_chip_index - d_offset;
}
d_code_gen.get_chips( d_sv, first_p_chip_index,
num_chips*d_downsample_factor, d_pcode_store );
dest.resize( num_chips );
@@ -64,6 +75,7 @@ bool SpirentPrsCodeGenerator::get_chips( uint64_t first_chip_index,
return true;
}
#include <iostream>
void SpirentPrsCodeGenerator::set_prn( int sv )
{
if( sv < 1 || sv > 50 )

48
src/tests/arithmetic/spirent_prs_code_generation_test.cc
View File

@@ -78,7 +78,17 @@ TEST(SpirentPrsTest, E1FirstChipsTest)
code_gen.get_chips( first_chip_index, num_chips, prs );
pcode_gen.get_chips( sv, downsample_factor*first_chip_index+offset, num_chips*downsample_factor, pcode );
uint64_t first_p_chip_index = downsample_factor*first_chip_index;
if( first_p_chip_index < offset )
{
first_p_chip_index = first_p_chip_index + code_gen.get_code_length() - offset;
}
else
{
first_p_chip_index = first_p_chip_index - offset;
}
pcode_gen.get_chips( sv, first_p_chip_index, num_chips*downsample_factor, pcode );
for( unsigned int ii = 0, jj = 0; ii < num_chips; ++ii, jj+=downsample_factor )
{
@@ -129,7 +139,17 @@ TEST(SpirentPrsTest, E6FirstChipsTest)
code_gen.get_chips( first_chip_index, num_chips, prs );
pcode_gen.get_chips( sv, downsample_factor*first_chip_index+offset, num_chips*downsample_factor, pcode );
uint64_t first_p_chip_index = downsample_factor*first_chip_index;
if( first_p_chip_index < offset )
{
first_p_chip_index = first_p_chip_index + code_gen.get_code_length() - offset;
}
else
{
first_p_chip_index = first_p_chip_index - offset;
}
pcode_gen.get_chips( sv, first_p_chip_index, num_chips*downsample_factor, pcode );
for( unsigned int ii = 0, jj = 0; ii < num_chips; ++ii, jj+=downsample_factor )
{
@@ -182,7 +202,17 @@ TEST(SpirentPrsTest, E1LastChipsTest)
code_gen.get_chips( first_chip_index, num_chips, prs );
pcode_gen.get_chips( sv, downsample_factor*first_chip_index+offset, num_chips*downsample_factor, pcode );
uint64_t first_p_chip_index = downsample_factor*first_chip_index;
if( first_p_chip_index < offset )
{
first_p_chip_index = first_p_chip_index + code_gen.get_code_length() - offset;
}
else
{
first_p_chip_index = first_p_chip_index - offset;
}
pcode_gen.get_chips( sv, first_p_chip_index, num_chips*downsample_factor, pcode );
for( unsigned int ii = 0, jj = 0; ii < num_chips; ++ii, jj+=downsample_factor )
{
@@ -233,7 +263,17 @@ TEST(SpirentPrsTest, E6LastChipsTest)
code_gen.get_chips( first_chip_index, num_chips, prs );
pcode_gen.get_chips( sv, downsample_factor*first_chip_index+offset, num_chips*downsample_factor, pcode );
uint64_t first_p_chip_index = downsample_factor*first_chip_index;
if( first_p_chip_index < offset )
{
first_p_chip_index = first_p_chip_index + code_gen.get_code_length() - offset;
}
else
{
first_p_chip_index = first_p_chip_index - offset;
}
pcode_gen.get_chips( sv, first_p_chip_index, num_chips*downsample_factor, pcode );
for( unsigned int ii = 0, jj = 0; ii < num_chips; ++ii, jj+=downsample_factor )
{