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transceiver: Properly handle MAXDLY. 

Previously MAXDLY value was applied to Normal Bursts, which was nice
when working with sloppy test equipment like CMD57, but useless for
real world usage. At the same time documentation and de facto usage
of MAXDLY in OsmoBTS and OpenBTS assumed that it actually applies to
Access Bursts (RACH). So this patch changes osmo-rx behavior to apply
MAXDLY to RACH bursts and introduces a new command MAXDLYNB for the
old behavior.
This commit is contained in:
Alexander Chemeris 2016-03-19 21:16:22 +03:00 committed by Tom Tsou
parent a8cf208616
commit 78d1fc9a13
4 changed files with 24 additions and 11 deletions
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19
Transceiver52M/Transceiver.cpp
View File

@ -119,7 +119,8 @@ Transceiver::Transceiver(int wBasePort,
mTransmitLatency(wTransmitLatency), mRadioInterface(wRadioInterface),
rssiOffset(wRssiOffset),
mSPSTx(tx_sps), mSPSRx(rx_sps), mChans(chans), mOn(false),
mTxFreq(0.0), mRxFreq(0.0), mTSC(0), mMaxExpectedDelay(0), mWriteBurstToDiskMask(0)
mTxFreq(0.0), mRxFreq(0.0), mTSC(0), mMaxExpectedDelayAB(0), mMaxExpectedDelayNB(0),
mWriteBurstToDiskMask(0)
{
txFullScale = mRadioInterface->fullScaleInputValue();
rxFullScale = mRadioInterface->fullScaleOutputValue();
@ -535,18 +536,19 @@ int Transceiver::detectBurst(TransceiverState *state, signalVector &burst,
switch (type) {
case EDGE:
rc = detectEdgeBurst(burst, mTSC, threshold, mSPSRx,
amp, toa, mMaxExpectedDelay);
amp, toa, mMaxExpectedDelayNB);
if (rc > 0)
break;
else
type = TSC;
case TSC:
rc = analyzeTrafficBurst(burst, mTSC, threshold, mSPSRx,
amp, toa, mMaxExpectedDelay);
amp, toa, mMaxExpectedDelayNB);
break;
case RACH:
threshold = 6.0;
rc = detectRACHBurst(burst, threshold, mSPSRx, amp, toa);
rc = detectRACHBurst(burst, threshold, mSPSRx, amp, toa,
mMaxExpectedDelayAB);
break;
default:
LOG(ERR) << "Invalid correlation type";
@ -753,9 +755,16 @@ void Transceiver::driveControl(size_t chan)
//set expected maximum time-of-arrival
int maxDelay;
sscanf(buffer,"%3s %s %d",cmdcheck,command,&maxDelay);
mMaxExpectedDelay = maxDelay; // 1 GSM symbol is approx. 1 km
mMaxExpectedDelayAB = maxDelay; // 1 GSM symbol is approx. 1 km
sprintf(response,"RSP SETMAXDLY 0 %d",maxDelay);
}
else if (strcmp(command,"SETMAXDLYNB")==0) {
//set expected maximum time-of-arrival
int maxDelay;
sscanf(buffer,"%3s %s %d",cmdcheck,command,&maxDelay);
mMaxExpectedDelayNB = maxDelay; // 1 GSM symbol is approx. 1 km
sprintf(response,"RSP SETMAXDLYNB 0 %d",maxDelay);
}
else if (strcmp(command,"SETRXGAIN")==0) {
//set expected maximum time-of-arrival
int newGain;

3
Transceiver52M/Transceiver.h
View File

@ -227,7 +227,8 @@ private:
double mTxFreq; ///< the transmit frequency
double mRxFreq; ///< the receive frequency
unsigned mTSC; ///< the midamble sequence code
unsigned mMaxExpectedDelay; ///< maximum expected time-of-arrival offset in GSM symbols
unsigned mMaxExpectedDelayAB; ///< maximum expected time-of-arrival offset in GSM symbols for Access Bursts (RACH)
unsigned mMaxExpectedDelayNB; ///< maximum expected time-of-arrival offset in GSM symbols for Normal Bursts
unsigned mWriteBurstToDiskMask; ///< debug: bitmask to indicate which timeslots to dump to disk
std::vector<TransceiverState> mStates;

9
Transceiver52M/sigProcLib.cpp
View File

@ -1816,21 +1816,22 @@ int detectGeneralBurst(signalVector &rxBurst,
*
* Correlation window parameters:
* target: Tail bits + RACH length (reduced from 41 to a multiple of 4)
* head: Search 4 symbols before target
* tail: Search 10 symbols after target
* head: Search 4 symbols before target
* tail: Search 4 symbols + maximum expected delay
*/
int detectRACHBurst(signalVector &rxBurst,
float thresh,
int sps,
complex &amp,
float &toa)
float &toa,
unsigned maxTOA)
{
int rc, target, head, tail;
CorrelationSequence *sync;
target = 8 + 40;
head = 4;
tail = 10;
tail = 4 + maxTOA;
sync = gRACHSequence;
rc = detectGeneralBurst(rxBurst, thresh, sps, amp, toa,

4
Transceiver52M/sigProcLib.h
View File

@ -192,13 +192,15 @@ bool energyDetect(signalVector &rxBurst,
@param sps The number of samples per GSM symbol.
@param amplitude The estimated amplitude of received RACH burst.
@param TOA The estimate time-of-arrival of received RACH burst.
@param maxTOA The maximum expected time-of-arrival
@return positive if threshold value is reached, negative on error, zero otherwise
*/
int detectRACHBurst(signalVector &rxBurst,
float detectThreshold,
int sps,
complex &amplitude,
float &TOA);
float &TOA,
unsigned maxTOA);
/**
Normal burst correlator, detector, channel estimator.