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sigproc: Add clipping detection on RACH and TSC input

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Alert user of overdriven burst input indicated by a positive
threshold detector result. This indication serves as notification
that the receive RF gain level is too high for the configured
transceiver setup.

Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
This commit is contained in:
Tom Tsou
2015-05-18 13:57:54 -07:00
parent 88bbf1aafd
commit 577cd020c1
3 changed files with 43 additions and 6 deletions
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29
Transceiver52M/sigProcLib.cpp
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@@ -40,6 +40,9 @@ using namespace GSM;
#define TABLESIZE 1024
#define DELAYFILTS 64
/* Clipping detection threshold */
#define CLIP_THRESH 30000.0f
/** Lookup tables for trigonometric approximation */
float cosTable[TABLESIZE+1]; // add 1 element for wrap around
float sinTable[TABLESIZE+1];
@@ -1369,6 +1372,18 @@ static int detectBurst(signalVector &burst,
return 1;
}
static int detectClipping(signalVector &burst, float thresh)
{
for (size_t i = 0; i < burst.size(); i++) {
if (fabs(burst[i].real()) > thresh)
return 1;
if (fabs(burst[i].imag()) > thresh)
return 1;
}
return 0;
}
/*
* RACH burst detection
*
@@ -1390,7 +1405,10 @@ int detectRACHBurst(signalVector &rxBurst,
CorrelationSequence *sync;
if ((sps != 1) && (sps != 4))
return -1;
return -SIGERR_UNSUPPORTED;
if (detectClipping(rxBurst, CLIP_THRESH))
return -SIGERR_CLIP;
target = 8 + 40;
head = 4;
@@ -1406,7 +1424,7 @@ int detectRACHBurst(signalVector &rxBurst,
delete corr;
if (rc < 0) {
return -1;
return -SIGERR_INTERNAL;
} else if (!rc) {
if (amp)
*amp = 0.0f;
@@ -1443,7 +1461,10 @@ int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
CorrelationSequence *sync;
if ((tsc < 0) || (tsc > 7) || ((sps != 1) && (sps != 4)))
return -1;
return -SIGERR_UNSUPPORTED;
if (detectClipping(rxBurst, CLIP_THRESH))
return -SIGERR_CLIP;
target = 3 + 58 + 16 + 5;
head = 4;
@@ -1459,7 +1480,7 @@ int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
delete corr;
if (rc < 0) {
return -1;
return -SIGERR_INTERNAL;
} else if (!rc) {
if (amp)
*amp = 0.0f;