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-rw-r--r--Transceiver52M/Transceiver.cpp147
1 files changed, 127 insertions, 20 deletions
diff --git a/Transceiver52M/Transceiver.cpp b/Transceiver52M/Transceiver.cpp
index a4eda4b..d7b2da3 100644
--- a/Transceiver52M/Transceiver.cpp
+++ b/Transceiver52M/Transceiver.cpp
@@ -621,14 +621,28 @@ int Transceiver::detectTSC(TransceiverState *state, signalVector &burst,
return 1;
}
+void writeToFile(signalVector *burst, const GSM::Time &time, size_t chan, const std::string postfix="")
+{
+ std::ostringstream fname;
+ fname << chan << "_" << time.FN() << "_" << time.TN() << postfix << ".fc";
+ std::ofstream outfile(fname.str().c_str(), std::ofstream::binary);
+ outfile.write((char*)burst->begin(), burst->size() * 2 * sizeof(float));
+ outfile.close();
+}
+
/*
* Demodulate GMSK burst using equalization if requested. Otherwise
* demodulate by direct rotation and soft slicing.
*/
SoftVector *Transceiver::demodulate(TransceiverState *state,
signalVector &burst, complex amp,
- float toa, size_t tn, bool equalize)
+ float toa, size_t tn, bool equalize,
+ GSM::Time &wTime, size_t chan)
{
+ signalVector *aligned, *bit_aligned=NULL;
+ SoftVector *bits;
+ bool estimateQuality = true;
+
if (equalize) {
scaleVector(burst, complex(1.0, 0.0) / amp);
return equalizeBurst(burst,
@@ -638,17 +652,28 @@ SoftVector *Transceiver::demodulate(TransceiverState *state,
*state->DFEFeedback[tn]);
}
- return demodulateBurst(burst, mSPSRx, amp, toa);
-}
+ aligned = alignBurst(burst, amp, toa);
-void writeToFile(radioVector *radio_burst, size_t chan)
-{
- GSM::Time time = radio_burst->getTime();
- std::ostringstream fname;
- fname << chan << "_" << time.FN() << "_" << time.TN() << ".fc";
- std::ofstream outfile (fname.str().c_str(), std::ofstream::binary);
- outfile.write((char*)radio_burst->getVector()->begin(), radio_burst->getVector()->size() * 2 * sizeof(float));
- outfile.close();
+ if (estimateQuality) {
+ /* "aligned" burst has samples exactly between bits.
+ * Delay it by 1/2 bit more to get samples aligned to bit positions. */
+ bit_aligned = delayVector(aligned, NULL, 0.5);
+
+ /* Debug: dump bursts to disk */
+ if (needWriteBurstToDisk(wTime, chan))
+ writeToFile(bit_aligned, wTime, chan, "_aligned");
+ }
+
+ bits = demodulateBurst(*aligned, mSPSRx);
+
+ if (estimateQuality) {
+ /* Estimate signal quality */
+ estimateBurstQuality(bits->segment(0, gSlotLen).sliced(), bit_aligned, wTime, chan);
+ delete bit_aligned;
+ }
+
+ delete aligned;
+ return bits;
}
/*
@@ -679,10 +704,8 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI, bool &i
CorrType type = expectedCorrType(time, chan);
/* Debug: dump bursts to disk */
- /* bits 0-7 - chan 0 timeslots
- * bits 8-15 - chan 1 timeslots */
- if (mWriteBurstToDiskMask & ((1<<time.TN()) << (8*chan)))
- writeToFile(radio_burst, chan);
+ if (needWriteBurstToDisk(time, chan))
+ writeToFile(radio_burst->getVector(), time, chan);
/* No processing if the timeslot is off.
* Not even power level or noise calculation. */
@@ -754,7 +777,7 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime, double &RSSI, bool &i
if (equalize && (type != TSC))
equalize = false;
- bits = demodulate(state, *burst, amp, toa, time.TN(), equalize);
+ bits = demodulate(state, *burst, amp, toa, time.TN(), equalize, time, chan);
delete radio_burst;
return bits;
@@ -978,6 +1001,89 @@ void Transceiver::driveReceiveRadio()
}
}
+inline float wrapAngle2Pi(float angle)
+{
+ const float twoPi = 2.0 * M_PI;
+ return angle - twoPi * floor( angle / twoPi );
+}
+
+inline float wrapAnglePi(float angle)
+{
+ const float twoPi = 2.0 * M_PI;
+ return angle - twoPi * floor( (angle+M_PI) / twoPi);
+}
+
+inline float rad2deg(float rad)
+{
+ return rad*180/M_PI;
+}
+
+inline int vectorMaxAbs(const Vector<float> &vec)
+{
+ int max_idx = 0;
+ float max = 0.0;
+ for (size_t i=1; i<vec.size(); i++) {
+ if (fabs(vec[i]) > max) {
+ max_idx = i;
+ max = fabs(vec[i]);
+ }
+ }
+ return max_idx;
+}
+
+inline float vectorRMS(const Vector<float> &vec)
+{
+ float rms = 0;
+ for (size_t i=1; i<vec.size(); i++) {
+ rms += vec[i]*vec[i];
+ }
+ return sqrt(rms/vec.size());
+}
+
+void Transceiver::estimateBurstQuality(const BitVector &wBits, signalVector *received,
+ const GSM::Time &wTime, size_t chan)
+{
+ signalVector *burst;
+ Vector<float> phase_err(148); // 148 bits - burst length including guard bits
+ Vector<float> phase_err_deg(148); // 148 bits - burst length including guard bits
+ int phase_err_max;
+ float phase_err_rms;
+
+ // this code supports only 4 SPS modulation
+ // we also assume that received vector is 1 SPS
+ assert(mSPSTx==4);
+
+ burst = modulateBurst(wBits, 8 + (wTime.TN() % 4 == 0), mSPSTx);
+
+ /* Debug: dump bursts to disk */
+ if (needWriteBurstToDisk(wTime, chan))
+ writeToFile(burst, wTime, chan, "_demod");
+
+ // flip values to align modulated format with the received format
+ for (size_t i=0; i<burst->size(); i++) {
+ (*burst)[i] = complex((*burst)[i].imag(), -(*burst)[i].real());
+ }
+
+ // calculate phase error for each bit
+ for (size_t i=0; i<phase_err.size(); i++) {
+ float rx_phase = (*received)[i].arg();
+ float mod_phase = (*burst)[1+(2+i)*4].arg();
+ phase_err[i] = wrapAnglePi(rx_phase - mod_phase);
+ phase_err_deg[i] = rad2deg(phase_err[i]);
+ }
+
+ phase_err_max = vectorMaxAbs(phase_err);
+ phase_err_rms = vectorRMS(phase_err);
+
+ LOG(INFO) << std::fixed << std::right << "Phase Error time: " << wTime
+ << " peak: " << std::setw(5) << std::setprecision(1) << phase_err_deg[phase_err_max]
+ << " @bit " << std::setw(3) << phase_err_max
+ << " RMS: " << std::setw(5) << std::setprecision(1) << rad2deg(phase_err_rms)
+ << " bits: " << std::setw(5) << std::setprecision(1) << phase_err_deg;
+
+ delete burst;
+}
+
void Transceiver::driveReceiveFIFO(size_t chan)
{
SoftVector *rxBurst = NULL;
@@ -995,11 +1101,12 @@ void Transceiver::driveReceiveFIFO(size_t chan)
dBm = RSSI+rssiOffset;
TOAint = (int) (TOA * 256.0 + 0.5); // round to closest integer
- LOG(DEBUG) << std::fixed << std::right
+ LOG(INFO) << 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
+ << " 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
+ << " energy: " << std::setw(5) << std::setprecision(2) << rxBurst->getEnergy()
<< " bits: " << *rxBurst;
char burstString[gSlotLen+10];
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-24 19:16:28 +0000