Transceiver52M: Fix calculation of TS correlation for 2 sps and higher

The correlation starting point for normal burst training sequence
calculation should be a scaled value of the same symbol regardless
of the samples-per-symbol used. Use of 2 samples-per-symbols double
the index values, but yields the following outputs, which results
in a late time-of-arrival value at the output of the correlation.

This patch modifies the parameter calculation accordingly.

1 sps parameters

maxTOA = 3
spanTOA = 5;
startIx = 61;
endIx = 87;
windowLen = 26;
corrLen = 7;

2 sps parameters (errant case)

maxTOA = 6;
spanTOA = 10;
startIx = 112;
endIx = 184;
windowLen = 72;
corrLen =13;

2 sps parameters (corrected)

maxTOA = 6;
spanTOA = 10;
startIx = 122;
endIx = 174;
windowLen = 52;
corrLen =13;

Signed-off-by: Thomas Tsou <tom@tsou.cc>

git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@5183 19bc5d8c-e614-43d4-8b26-e1612bc8e597

1 files changed, 2 insertions, 2 deletions

diff --git a/Transceiver52M/sigProcLib.cpp b/Transceiver52M/sigProcLib.cpp
index ae52894..5dc2def 100644
--- a/Transceiver52M/sigProcLib.cpp
+++ b/Transceiver52M/sigProcLib.cpp
@@ -1018,8 +1018,8 @@ bool analyzeTrafficBurst(signalVector &rxBurst,
   unsigned spanTOA = maxTOA;
   if (spanTOA < 5*samplesPerSymbol) spanTOA = 5*samplesPerSymbol;
 
-  unsigned startIx = (66-spanTOA)*samplesPerSymbol;
-  unsigned endIx = (66+16+spanTOA)*samplesPerSymbol;
+  unsigned startIx = 66*samplesPerSymbol-spanTOA;
+  unsigned endIx = (66+16)*samplesPerSymbol+spanTOA;
   unsigned windowLen = endIx - startIx;
   unsigned corrLen = 2*maxTOA+1;