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Transceiver: Update noise level only when the timeslot is marked as IDLE. 

We can't rely on an assumption that if we can't decode a burst - it's noise.
There are many rasons why we can't decode a burst even if it's well above the
noise level. Just one example is a RACH burst which can be overlapped with
another RACH burst up to a level both are completely unrecognizable. Another
example is when a burst is destroyed by bad multi-path.
This commit is contained in:
Alexander Chemeris 2015-06-08 22:46:38 -04:00
parent 37b445d4c8
commit f0d8a581b4
2 changed files with 32 additions and 16 deletions
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46
Transceiver52M/Transceiver.cpp
View File

@ -620,7 +620,7 @@ SoftVector *Transceiver::demodulate(TransceiverState *state,
* Pull bursts from the FIFO and handle according to the slot
* and burst correlation type. Equalzation is currently disabled.
*/
SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI,
SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI, bool &isRssiValid,
double &timingOffset, double &noise,
size_t chan)
{
@ -632,6 +632,7 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI,
signalVector *burst;
SoftVector *bits = NULL;
TransceiverState *state = &mStates[chan];
isRssiValid = false;
/* Blocking FIFO read */
radioVector *radio_burst = mReceiveFIFO[chan]->read();
@ -642,7 +643,9 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI,
GSM::Time time = radio_burst->getTime();
CorrType type = expectedCorrType(time, chan);
if ((type == OFF) || (type == IDLE)) {
/* No processing if the timeslot is off.
* Not even power level or noise calculation. */
if (type == OFF) {
delete radio_burst;
return NULL;
}
@ -666,7 +669,25 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI,
/* Average noise on diversity paths and update global levels */
burst = radio_burst->getVector(max_i);
avg = sqrt(avg / radio_burst->chans());
state->mNoiseLev = state->mNoises.avg();
wTime = time;
RSSI = 20.0 * log10(rxFullScale / avg);
/* RSSI estimation are valid */
isRssiValid = true;
if (type == IDLE) {
/* Update noise levels */
state->mNoises.insert(avg);
state->mNoiseLev = state->mNoises.avg();
noise = 20.0 * log10(rxFullScale / state->mNoiseLev);
delete radio_burst;
return NULL;
} else {
/* Do not update noise levels */
noise = 20.0 * log10(rxFullScale / state->mNoiseLev);
}
/* Detect normal or RACH bursts */
if (type == TSC)
@ -674,13 +695,11 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI,
else
success = detectRACH(state, *burst, amp, toa);
/* Update noise average if no bust detected or alert on error */
/* Alert an error and exit */
if (success <= 0) {
if (success == SIGERR_NONE) {
state->mNoises.insert(avg);
} else if (success == -SIGERR_CLIP) {
if (success == -SIGERR_CLIP) {
LOG(WARNING) << "Clipping detected on received RACH or Normal Burst";
} else {
} else if (success != SIGERR_NONE) {
LOG(WARNING) << "Unhandled RACH or Normal Burst detection error";
}
@ -688,19 +707,15 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI,
return NULL;
}
timingOffset = toa / mSPSRx;
/* Demodulate and set output info */
if (equalize && (type != TSC))
equalize = false;
bits = demodulate(state, *burst, amp, toa, time.TN(), equalize);
wTime = time;
RSSI = 20.0 * log10(rxFullScale / avg);
timingOffset = toa / mSPSRx;
noise = 20.0 * log10(rxFullScale / state->mNoiseLev);
delete radio_burst;
return bits;
}
@ -905,8 +920,9 @@ void Transceiver::driveReceiveFIFO(size_t chan)
int TOAint; // in 1/256 symbols
double noise; // noise level in dBFS
GSM::Time burstTime;
bool isRssiValid; // are RSSI, noise and burstTime valid
rxBurst = pullRadioVector(burstTime, RSSI, TOA, noise, chan);
rxBurst = pullRadioVector(burstTime, RSSI, isRssiValid, TOA, noise, chan);
if (rxBurst) {
dBm = RSSI+rssiOffset;

2
Transceiver52M/Transceiver.h
View File

@ -195,7 +195,7 @@ private:
void pushRadioVector(GSM::Time &nowTime);
/** Pull and demodulate a burst from the receive FIFO */
SoftVector *pullRadioVector(GSM::Time &wTime, double &RSSI,
SoftVector *pullRadioVector(GSM::Time &wTime, double &RSSI, bool &isRssiValid,
double &timingOffset, double &noise,
size_t chan = 0);