Transceiver52M: Add clipping detection on RACH input
Alert user of overdriven RACH 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.cc>
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@ -523,10 +523,18 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, int &RSSI,
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else
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success = detectRACH(state, *burst, amp, toa);
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if (!success) {
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if (success == 0) {
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state->mNoises.insert(avg);
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delete radio_burst;
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return NULL;
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} else if (success < 0) {
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if (success == -SIGERR_CLIP) {
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LOG(ALERT) << "Clipping detected on RACH input";
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} else {
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LOG(ALERT) << "Unhandled RACH error";
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}
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delete radio_burst;
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return NULL;
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}
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/* Demodulate and set output info */
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@ -34,6 +34,8 @@ extern "C" {
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#include "scale.h"
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#include "mult.h"
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}
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/* Clipping detection threshold */
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#define CLIP_THRESH 30000.0f
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using namespace GSM;
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@ -1340,7 +1342,7 @@ static int detectBurst(signalVector &burst,
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/* Correlate */
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if (!convolve(&burst, sync->sequence, &corr,
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CUSTOM, start, len, sps, 0)) {
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return -1;
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return -SIGERR_INTERNAL;
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}
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/* Peak detection - place restrictions at correlation edges */
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@ -1369,6 +1371,18 @@ static int detectBurst(signalVector &burst,
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return 1;
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}
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static int detectClipping(signalVector &burst, float thresh)
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{
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for (size_t i = 0; i < burst.size(); i++) {
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if (fabs(burst[i].real()) > thresh)
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return 1;
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if (fabs(burst[i].imag()) > thresh)
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return 1;
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}
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return 0;
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}
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/*
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* RACH burst detection
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*
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@ -1390,7 +1404,10 @@ int detectRACHBurst(signalVector &rxBurst,
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CorrelationSequence *sync;
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if ((sps != 1) && (sps != 4))
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return -1;
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return -SIGERR_UNSUPPORTED;
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if (detectClipping(rxBurst, CLIP_THRESH))
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return -SIGERR_CLIP;
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target = 8 + 40;
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head = 4;
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@ -1443,7 +1460,7 @@ int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
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CorrelationSequence *sync;
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if ((tsc < 0) || (tsc > 7) || ((sps != 1) && (sps != 4)))
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return -1;
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return -SIGERR_UNSUPPORTED;
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target = 3 + 58 + 16 + 5;
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head = 4;
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@ -1459,7 +1476,7 @@ int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
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delete corr;
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if (rc < 0) {
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return -1;
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return -SIGERR_INTERNAL;
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} else if (!rc) {
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if (amp)
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*amp = 0.0f;
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@ -28,6 +28,14 @@ enum ConvType {
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UNDEFINED,
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};
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enum signalError {
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SIGERR_NONE,
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SIGERR_BOUNDS,
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SIGERR_CLIP,
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SIGERR_UNSUPPORTED,
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SIGERR_INTERNAL,
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};
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/** Convert a linear number to a dB value */
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float dB(float x);
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