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Transceiver52M: Disable energy detector

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The adaptive energy threshold gating suffers a near-far problem
at certain gain levels. This is due to exponential threshold
raising, but linear decreases. A large signal level followed by
a period low signal level causes (comparatively) weak signals to
go undetected. Additionally, the algorithm performs differently
at multiple RF gain levels.

This patch switches solely to correlation based gating for burst
detection. The main computational load with this approach is
sub-sample width peak interpolation, which we disable for intial
detection and run after threshold passing.

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

git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6735 19bc5d8c-e614-43d4-8b26-e1612bc8e597
This commit is contained in:
Thomas Tsou
2013-10-17 06:18:22 +00:00
parent 7251140a21
commit 1d7e468b06
2 changed files with 32 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
Transceiver52M/Transceiver.cpp
View File

@@ -350,6 +350,7 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime,
complex amplitude = 0.0;
float TOA = 0.0;
float avgPwr = 0.0;
#ifdef ENERGY_DETECT
if (!energyDetect(*vectorBurst, 20 * mSPS, mEnergyThreshold, &avgPwr)) {
LOG(DEBUG) << "Estimated Energy: " << sqrt(avgPwr) << ", at time " << rxBurst->getTime();
double framesElapsed = rxBurst->getTime()-prevFalseDetectionTime;
@@ -364,7 +365,7 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime,
return NULL;
}
LOG(DEBUG) << "Estimated Energy: " << sqrt(avgPwr) << ", at time " << rxBurst->getTime();
#endif
// run the proper correlator
bool success = false;
if (corrType==TSC) {

33
Transceiver52M/sigProcLib.cpp
View File

@@ -651,8 +651,27 @@ complex interpolatePoint(const signalVector &inSig,
return pVal;
}
static complex fastPeakDetect(const signalVector &rxBurst, float *index)
{
float val, max = 0.0f;
complex amp;
int _index = -1;
for (int i = 0; i < rxBurst.size(); i++) {
val = rxBurst[i].norm2();
if (val > max) {
max = val;
_index = i;
amp = rxBurst[i];
}
}
if (index)
*index = (float) _index;
return amp;
}
complex peakDetect(const signalVector &rxBurst,
float *peakIndex,
float *avgPwr)
@@ -926,12 +945,15 @@ int detectRACHBurst(signalVector &rxBurst,
return -1;
}
_amp = peakDetect(corr, &_toa, NULL);
_amp = fastPeakDetect(corr, &_toa);
/* Restrict peak-to-average calculations at the edges */
if ((_toa < 3) || (_toa > len - 3))
goto notfound;
peak = corr.begin() + (int) rint(_toa);
/* Compute peak-to-average ratio. Reject if we don't have enough values */
for (int i = 2 * sps; i <= 5 * sps; i++) {
if (peak - i >= corr.begin()) {
avg += (peak - i)->norm2();
@@ -951,9 +973,14 @@ int detectRACHBurst(signalVector &rxBurst,
if (par < thresh)
goto notfound;
/* Run the full peak detection to obtain interpolated values */
_amp = peakDetect(corr, &_toa, NULL);
/* Subtract forward tail bits from delay */
if (toa)
*toa = _toa - 8 * sps;
/* Normalize our channel gain */
if (amp)
*amp = _amp / gRACHSequence->gain;