sigproc: Setup downlink bursts at 156.25 duration with 4 SPS

Instead of extending 156/157 symbol sized bursts to 624/628 when 4
samples-per-symbol are used, use a fixed size of 625 samples, or
625.25 us.

This is a breaking timing change.

CommonLibs/Logger.cpp

@@ -206,7 +206,7 @@ Log::~Log()
 	if (gLogToConsole||gLogToFile) {
 		int mlen = mStream.str().size();
 		int neednl = (mlen==0 || mStream.str()[mlen-1] != '\n');
-		gLogToLock.lock();
+		ScopedLock lock(gLogToLock);
 		if (gLogToConsole) {
 			// The COUT() macro prevents messages from stomping each other but adds uninteresting thread numbers,
 			// so just use std::cout.
@@ -218,7 +218,6 @@ Log::~Log()
 			if (neednl) {fputc('\n',gLogToFile);}
 			fflush(gLogToFile);
 		}
-		gLogToLock.unlock();
 	}
 }
 

Transceiver52M/Transceiver.cpp

@@ -22,6 +22,7 @@
 */
 
 #include <stdio.h>
+#include <iomanip>      // std::setprecision
 #include "Transceiver.h"
 #include <Logger.h>
 
@@ -140,13 +141,15 @@ bool TransceiverState::init(int filler, size_t sps, float scale, size_t rtsc)
 }
 
 Transceiver::Transceiver(int wBasePort,
-			 const char *wTRXAddress,
-			 size_t wSPS, size_t wChans,
-			 GSM::Time wTransmitLatency,
-			 RadioInterface *wRadioInterface)
+                         const char *wTRXAddress,
+                         size_t wSPS, size_t wChans,
+                         GSM::Time wTransmitLatency,
+                         RadioInterface *wRadioInterface,
+                         double wRssiOffset)
   : mBasePort(wBasePort), mAddr(wTRXAddress),
     mClockSocket(wBasePort, wTRXAddress, mBasePort + 100),
     mTransmitLatency(wTransmitLatency), mRadioInterface(wRadioInterface),
+    rssiOffset(wRssiOffset),
     mSPSTx(wSPS), mSPSRx(1), mChans(wChans), mOn(false),
     mTxFreq(0.0), mRxFreq(0.0), mTSC(0), mMaxExpectedDelay(0)
 {
@@ -531,9 +534,9 @@ Transceiver::CorrType Transceiver::expectedCorrType(GSM::Time currTime,
  * Detect RACH synchronization sequence within a burst. No equalization
  * is used or available on the RACH channel.
  */
-bool Transceiver::detectRACH(TransceiverState *state,
-                             signalVector &burst,
-                             complex &amp, float &toa)
+int Transceiver::detectRACH(TransceiverState *state,
+                            signalVector &burst,
+                            complex &amp, float &toa)
 {
   float threshold = 6.0;
 
@@ -545,9 +548,10 @@ bool Transceiver::detectRACH(TransceiverState *state,
  * state information and channel estimate if necessary. Equalization
  * is currently disabled.
  */
-bool Transceiver::detectTSC(TransceiverState *state, signalVector &burst,
-                            complex &amp, float &toa, GSM::Time &time)
+int Transceiver::detectTSC(TransceiverState *state, signalVector &burst,
+                           complex &amp, float &toa, GSM::Time &time)
 {
+  int success;
   int tn = time.TN();
   float chanOffset, threshold = 5.0;
   bool noise, needDFE = false, estimateChan = false;
@@ -565,10 +569,11 @@ bool Transceiver::detectTSC(TransceiverState *state, signalVector &burst,
   }
 
   /* Detect normal burst midambles */
-  if (!analyzeTrafficBurst(burst, mTSC, threshold, mSPSRx, &amp,
-                           &toa, mMaxExpectedDelay, estimateChan,
-                           &chanResp, &chanOffset)) {
-    return false;
+  success = analyzeTrafficBurst(burst, mTSC, threshold, mSPSRx, &amp,
+                                &toa, mMaxExpectedDelay, estimateChan,
+                                &chanResp, &chanOffset);
+  if (success <= 0) {
+    return success;
   }
 
   noise = state->mNoiseLev;
@@ -588,7 +593,7 @@ bool Transceiver::detectTSC(TransceiverState *state, signalVector &burst,
      state->chanEstimateTime[tn] = time;
   }
 
-  return true;;
+  return 1;
 }
 
 /*
@@ -615,10 +620,12 @@ 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, int &RSSI,
-                                         int &timingOffset, size_t chan)
+SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI,
+                                         double &timingOffset, double &noise,
+                                         size_t chan)
 {
-  bool success, equalize = false;
+  int success;
+  bool equalize = false;
   complex amp;
   float toa, pow, max = -1.0, avg = 0.0;
   int max_i = -1;
@@ -669,12 +676,12 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, int &RSSI,
 
   /* Update noise average if no bust detected or alert on error */
   if (success <= 0) {
-    if (!success) {
+    if (success == SIGERR_NONE) {
       state->mNoises.insert(avg);
     } else if (success == -SIGERR_CLIP) {
-      LOG(ALERT) << "Clipping detected on RACH input";
-    } else if (success < 0) {
-      LOG(ALERT) << "Unhandled RACH error";
+      LOG(WARNING) << "Clipping detected on received RACH or Normal Burst";
+    } else {
+      LOG(WARNING) << "Unhandled RACH or Normal Burst detection error";
     }
 
     delete radio_burst;
@@ -689,8 +696,9 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, int &RSSI,
     bits = demodulate(state, *burst, amp, toa, time.TN(), equalize);
 
   wTime = time;
-  RSSI = (int) floor(20.0 * log10(rxFullScale / avg));
-  timingOffset = (int) round(toa * 256.0 / mSPSRx);
+  RSSI = 20.0 * log10(rxFullScale / avg);
+  timingOffset = toa / mSPSRx;
+  noise = 20.0 * log10(rxFullScale / state->mNoiseLev);
 
   delete radio_burst;
 
@@ -892,27 +900,33 @@ void Transceiver::driveReceiveRadio()
 void Transceiver::driveReceiveFIFO(size_t chan)
 {
   SoftVector *rxBurst = NULL;
-  int RSSI;
-  int TOA;  // in 1/256 of a symbol
+  double RSSI; // in dBFS
+  double dBm;  // in dBm
+  double TOA;  // in symbols
+  int TOAint;  // in 1/256 symbols
+  double noise; // noise level in dBFS
   GSM::Time burstTime;
 
-  rxBurst = pullRadioVector(burstTime, RSSI, TOA, chan);
+  rxBurst = pullRadioVector(burstTime, RSSI, TOA, noise, chan);
 
   if (rxBurst) { 
+    dBm = RSSI+rssiOffset;
+    TOAint = (int) (TOA * 256.0 + 0.5); // round to closest integer
+
+	LOG(DEBUG) << std::fixed << std::right
+      << " time: "   << burstTime
+	  << " RSSI: "   << std::setw(5) << std::setprecision(1) << RSSI << "dBFS/" << std::setw(6) << -dBm << "dBm"
+	  << " noise: "  << std::setw(5) << std::setprecision(1) << noise << "dBFS/" << std::setw(6) << -(noise+rssiOffset) << "dBm"
+	  << " TOA: "    << std::setw(5) << std::setprecision(2) << TOA
+      << " bits: "   << *rxBurst;
 
-    LOG(DEBUG) << "burst parameters: "
-	  << " time: " << burstTime
-	  << " RSSI: " << RSSI
-	  << " TOA: "  << TOA
-	  << " bits: " << *rxBurst;
-    
     char burstString[gSlotLen+10];
     burstString[0] = burstTime.TN();
     for (int i = 0; i < 4; i++)
       burstString[1+i] = (burstTime.FN() >> ((3-i)*8)) & 0x0ff;
-    burstString[5] = RSSI;
-    burstString[6] = (TOA >> 8) & 0x0ff;
-    burstString[7] = TOA & 0x0ff;
+    burstString[5] = (int)dBm;
+    burstString[6] = (TOAint >> 8) & 0x0ff;
+    burstString[7] = TOAint & 0x0ff;
     SoftVector::iterator burstItr = rxBurst->begin();
 
     for (unsigned int i = 0; i < gSlotLen; i++) {

Transceiver52M/Transceiver.h

@@ -97,10 +97,11 @@ public:
       @param radioInterface associated radioInterface object
   */
   Transceiver(int wBasePort,
-	      const char *TRXAddress,
-	      size_t wSPS, size_t chans,
-	      GSM::Time wTransmitLatency,
-	      RadioInterface *wRadioInterface);
+              const char *TRXAddress,
+              size_t wSPS, size_t chans,
+              GSM::Time wTransmitLatency,
+              RadioInterface *wRadioInterface,
+              double wRssiOffset);
 
   /** Destructor */
   ~Transceiver();
@@ -181,6 +182,8 @@ private:
   double txFullScale;                     ///< full scale input to radio
   double rxFullScale;                     ///< full scale output to radio
 
+  double rssiOffset;                      ///< RSSI to dBm conversion offset
+
   /** modulate and add a burst to the transmit queue */
   void addRadioVector(size_t chan, BitVector &bits,
                       int RSSI, GSM::Time &wTime);
@@ -192,8 +195,9 @@ private:
   void pushRadioVector(GSM::Time &nowTime);
 
   /** Pull and demodulate a burst from the receive FIFO */
-  SoftVector *pullRadioVector(GSM::Time &wTime, int &RSSI,
-                              int &timingOffset, size_t chan = 0);
+  SoftVector *pullRadioVector(GSM::Time &wTime, double &RSSI,
+                              double &timingOffset, double &noise,
+                              size_t chan = 0);
 
   /** Set modulus for specific timeslot */
   void setModulus(size_t timeslot, size_t chan);
@@ -205,14 +209,14 @@ private:
   void writeClockInterface(void);
 
   /** Detect RACH bursts */
-  bool detectRACH(TransceiverState *state,
-                  signalVector &burst,
-                  complex &amp, float &toa);
+  int detectRACH(TransceiverState *state,
+                 signalVector &burst,
+                 complex &amp, float &toa);
 
   /** Detect normal bursts */
-  bool detectTSC(TransceiverState *state,
-                 signalVector &burst,
-                 complex &amp, float &toa, GSM::Time &time);
+  int detectTSC(TransceiverState *state,
+                signalVector &burst,
+                complex &amp, float &toa, GSM::Time &time);
 
   /** Demodulat burst and output soft bits */
   SoftVector *demodulate(TransceiverState *state,

Transceiver52M/osmo-trx.cpp

@@ -70,6 +70,7 @@ struct trx_config {
 	Transceiver::FillerType filler;
 	bool diversity;
 	double offset;
+	double rssi_offset;
 };
 
 ConfigurationTable gConfig;
@@ -185,6 +186,7 @@ bool trx_setup_config(struct trx_config *config)
 	ost << "   C0 Filler Table......... " << fillstr << std::endl;
 	ost << "   Diversity............... " << divstr << std::endl;
 	ost << "   Tuning offset........... " << config->offset << std::endl;
+	ost << "   RSSI to dBm offset...... " << config->rssi_offset << std::endl;
 	std::cout << ost << std::endl;
 
 	return true;
@@ -240,7 +242,7 @@ Transceiver *makeTransceiver(struct trx_config *config, RadioInterface *radio)
 	VectorFIFO *fifo;
 
 	trx = new Transceiver(config->port, config->addr.c_str(), config->sps,
-			      config->chans, GSM::Time(3,0), radio);
+		config->chans, GSM::Time(3,0), radio, config->rssi_offset);
 	if (!trx->init(config->filler, config->rtsc)) {
 		LOG(ALERT) << "Failed to initialize transceiver";
 		delete trx;
@@ -292,7 +294,8 @@ static void print_help()
 		"  -c    Number of ARFCN channels (default=1)\n"
 		"  -f    Enable C0 filler table\n"
 		"  -o    Set baseband frequency offset (default=auto)\n"
-		"  -r    Random burst test mode with TSC\n",
+		"  -r    Random burst test mode with TSC\n"
+		"  -R    RSSI to dBm offset in dB (default=0)\n",
 		"EMERG, ALERT, CRT, ERR, WARNING, NOTICE, INFO, DEBUG");
 }
 
@@ -308,8 +311,9 @@ static void handle_options(int argc, char **argv, struct trx_config *config)
 	config->filler = Transceiver::FILLER_ZERO;
 	config->diversity = false;
 	config->offset = 0.0;
+	config->rssi_offset = 0.0;
 
-	while ((option = getopt(argc, argv, "ha:l:i:p:c:dxfo:s:r:")) != -1) {
+	while ((option = getopt(argc, argv, "ha:l:i:p:c:dxfo:s:r:R:")) != -1) {
 		switch (option) {
 		case 'h':
 			print_help();
@@ -349,6 +353,9 @@ static void handle_options(int argc, char **argv, struct trx_config *config)
 			config->rtsc = atoi(optarg);
 			config->filler = Transceiver::FILLER_RAND;
 			break;
+		case 'R':
+			config->rssi_offset = atof(optarg);
+			break;
 		default:
 			print_help();
 			exit(0);

Transceiver52M/sigProcLib.cpp

@@ -28,6 +28,7 @@
 
 #include "sigProcLib.h"
 #include "GSMCommon.h"
+#include "Logger.h"
 
 extern "C" {
 #include "convolve.h"
@@ -43,6 +44,9 @@ using namespace GSM;
 /* Clipping detection threshold */
 #define CLIP_THRESH		30000.0f
 
+/* GSM 4 sps burst length */
+#define GSM_BURST_LEN_4SPS	625
+
 /** Lookup tables for trigonometric approximation */
 float cosTable[TABLESIZE+1]; // add 1 element for wrap around
 float sinTable[TABLESIZE+1];
@@ -696,27 +700,22 @@ static signalVector *rotateBurst(const BitVector &wBurst,
   return shaped;
 }
 
-static signalVector *modulateBurstLaurent(const BitVector &bits,
-					  int guard_len, int sps)
+/*
+ * Laurent decomposition based GMSK modulator - 4 SPS only
+ */
+static signalVector *modulateBurstLaurent(const BitVector &bits)
 {
-  int burst_len;
+  const int burst_len = GSM_BURST_LEN_4SPS;
+  const int sps = 4;
+
   float phase;
   signalVector *c0_pulse, *c1_pulse, *c0_burst;
   signalVector *c1_burst, *c0_shaped, *c1_shaped;
   signalVector::iterator c0_itr, c1_itr;
 
-  /*
-   * Apply before and after bits to reduce phase error at burst edges.
-   * Make sure there is enough room in the burst to accomodate all bits.
-   */
-  if (guard_len < 4)
-    guard_len = 4;
-
   c0_pulse = GSMPulse->c0;
   c1_pulse = GSMPulse->c1;
 
-  burst_len = sps * (bits.size() + guard_len);
-
   c0_burst = new signalVector(burst_len, c0_pulse->size());
   c0_burst->isReal(true);
   c0_itr = c0_burst->begin();
@@ -825,7 +824,7 @@ signalVector *modulateBurst(const BitVector &wBurst, int guardPeriodLength,
   if (emptyPulse)
     return rotateBurst(wBurst, guardPeriodLength, sps);
   else if (sps == 4)
-    return modulateBurstLaurent(wBurst, guardPeriodLength, sps);
+    return modulateBurstLaurent(wBurst);
   else
     return modulateBurstBasic(wBurst, guardPeriodLength, sps);
 }
@@ -1284,12 +1283,12 @@ static float computePeakRatio(signalVector *corr,
   complex *peak;
   float rms, avg = 0.0;
 
-  peak = corr->begin() + (int) rint(toa);
-
   /* Check for bogus results */
   if ((toa < 0.0) || (toa > corr->size()))
     return 0.0;
 
+  peak = corr->begin() + (int) rint(toa);
+
   for (int i = 2 * sps; i <= 5 * sps; i++) {
     if (peak - i >= corr->begin()) {
       avg += (peak - i)->norm2();
@@ -1372,16 +1371,17 @@ static int detectBurst(signalVector &burst,
   return 1;
 }
 
-static int detectClipping(signalVector &burst, float thresh)
+static float maxAmplitude(signalVector &burst)
 {
-	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;
-	}
+    float max = 0.0;
+    for (size_t i = 0; i < burst.size(); i++) {
+        if (fabs(burst[i].real()) > max)
+            max = fabs(burst[i].real());
+        if (fabs(burst[i].imag()) > max)
+            max = fabs(burst[i].imag());
+    }
 
-	return 0;
+    return max;
 }
 
 /* 
@@ -1399,6 +1399,7 @@ int detectRACHBurst(signalVector &rxBurst,
 		    float *toa)
 {
   int rc, start, target, head, tail, len;
+  bool clipping = false;
   float _toa;
   complex _amp;
   signalVector *corr;
@@ -1407,8 +1408,14 @@ int detectRACHBurst(signalVector &rxBurst,
   if ((sps != 1) && (sps != 4))
     return -SIGERR_UNSUPPORTED;
 
-  if (detectClipping(rxBurst, CLIP_THRESH))
-    return -SIGERR_CLIP;
+  // Detect potential clipping
+  // We still may be able to demod the burst, so we'll give it a try
+  // and only report clipping if we can't demod.
+  float maxAmpl = maxAmplitude(rxBurst);
+  if (maxAmpl > CLIP_THRESH) {
+    LOG(DEBUG) << "max burst amplitude: " << maxAmpl << " is above the clipping threshold: " << CLIP_THRESH << std::endl;
+    clipping = true;
+  }
 
   target = 8 + 40;
   head = 4;
@@ -1430,7 +1437,7 @@ int detectRACHBurst(signalVector &rxBurst,
       *amp = 0.0f;
     if (toa)
       *toa = 0.0f;
-    return 0;
+    return clipping?-SIGERR_CLIP:SIGERR_NONE;
   }
 
   /* Subtract forward search bits from delay */
@@ -1455,6 +1462,7 @@ int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
                         bool chan_req, signalVector **chan, float *chan_offset)
 {
   int rc, start, target, head, tail, len;
+  bool clipping = false;
   complex _amp;
   float _toa;
   signalVector *corr;
@@ -1463,8 +1471,14 @@ int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
   if ((tsc < 0) || (tsc > 7) || ((sps != 1) && (sps != 4)))
     return -SIGERR_UNSUPPORTED;
 
-  if (detectClipping(rxBurst, CLIP_THRESH))
-    return -SIGERR_CLIP;
+  // Detect potential clipping
+  // We still may be able to demod the burst, so we'll give it a try
+  // and only report clipping if we can't demod.
+  float maxAmpl = maxAmplitude(rxBurst);
+  if (maxAmpl > CLIP_THRESH) {
+    LOG(DEBUG) << "max burst amplitude: " << maxAmpl << " is above the clipping threshold: " << CLIP_THRESH << std::endl;
+    clipping = true;
+  }
 
   target = 3 + 58 + 16 + 5;
   head = 4;
@@ -1486,7 +1500,7 @@ int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
       *amp = 0.0f;
     if (toa)
       *toa = 0.0f;
-    return 0;
+    return clipping?-SIGERR_CLIP:SIGERR_NONE;
   }
 
   /* Subtract forward search bits from delay */