cellular-infrastructure
/
osmo-trx
mirror of https://gerrit.osmocom.org/osmo-trx
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

sigproc: Adjust burst detection threshold criteria 

Reduce the burst detection threshold to pass more bursts to upper
layers, but force stricter requirements on the computation itself.
For the latter, we now require at least 5 samples (rather than 2)
to compute a peak-to-average value.

End result is increased burst detection at low SNR conditions with
a small increase in false positive bursts when no signal is present.

Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
This commit is contained in:
Tom Tsou 2016-06-29 14:50:25 -07:00
parent 7676427816
commit a84e162672
2 changed files with 26 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
Transceiver52M/Transceiver.cpp
View File

@ -44,6 +44,15 @@ using namespace GSM;
/* Number of running values use in noise average */
#define NOISE_CNT 20
/*
* Burst detection threshold
*
* Decision threshold value for burst gating on peak-to-average value of
* correlated synchronization sequences. Lower values pass more bursts up
* to upper layers but will increase the false detection rate.
*/
#define BURST_THRESH 4.0
TransceiverState::TransceiverState()
: mRetrans(false), mNoiseLev(0.0), mNoises(NOISE_CNT), mPower(0.0)
{
@ -534,23 +543,22 @@ Transceiver::CorrType Transceiver::expectedCorrType(GSM::Time currTime,
int Transceiver::detectBurst(signalVector &burst,
complex &amp, float &toa, CorrType type)
{
float threshold = 5.0, rc = 0;
int rc = 0;
switch (type) {
case EDGE:
rc = detectEdgeBurst(burst, mTSC, threshold, mSPSRx,
rc = detectEdgeBurst(burst, mTSC, BURST_THRESH, mSPSRx,
amp, toa, mMaxExpectedDelayNB);
if (rc > 0)
break;
else
type = TSC;
case TSC:
rc = analyzeTrafficBurst(burst, mTSC, threshold, mSPSRx,
rc = analyzeTrafficBurst(burst, mTSC, BURST_THRESH, mSPSRx,
amp, toa, mMaxExpectedDelayNB);
break;
case RACH:
threshold = 6.0;
rc = detectRACHBurst(burst, threshold, mSPSRx, amp, toa,
rc = detectRACHBurst(burst, BURST_THRESH, mSPSRx, amp, toa,
mMaxExpectedDelayAB);
break;
default:

15
Transceiver52M/sigProcLib.cpp
View File

@ -1678,6 +1678,17 @@ release:
return status;
}
/*
* Peak-to-average computation +/- range from peak in symbols
*/
#define COMPUTE_PEAK_MIN 2
#define COMPUTE_PEAK_MAX 5
/*
* Minimum number of values needed to compute peak-to-average
*/
#define COMPUTE_PEAK_CNT 5
static float computePeakRatio(signalVector *corr,
int sps, float toa, complex amp)
{
@ -1691,7 +1702,7 @@ static float computePeakRatio(signalVector *corr,
peak = corr->begin() + (int) rint(toa);
for (int i = 2 * sps; i <= 5 * sps; i++) {
for (int i = COMPUTE_PEAK_MIN * sps; i <= COMPUTE_PEAK_MAX * sps; i++) {
if (peak - i >= corr->begin()) {
avg += (peak - i)->norm2();
num++;
@ -1702,7 +1713,7 @@ static float computePeakRatio(signalVector *corr,
}
}
if (num < 2)
if (num < COMPUTE_PEAK_CNT)
return 0.0;
rms = sqrtf(avg / (float) num) + 0.00001;