Transceiver52M: Make GSM pulse filter internal to implementation
There is no reason expose the pulse shaping filter outside of the
signal processing calls. The main transceiver object makes no use
of the filter and there's no reason to pass it around.
Initialize the pulse shape with the signal processing library, and
maintain an internal static member like many of the other library
variables. Similarly destroy the object when the library is closed.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
diff --git a/Transceiver52M/sigProcLib.cpp b/Transceiver52M/sigProcLib.cpp
index b7f3511..ab605cf 100644
--- a/Transceiver52M/sigProcLib.cpp
+++ b/Transceiver52M/sigProcLib.cpp
@@ -58,8 +58,27 @@
complex gain;
} CorrelationSequence;
+/*
+ * Gaussian and empty modulation pulses
+ */
+struct PulseSequence {
+ PulseSequence() : gaussian(NULL), empty(NULL)
+ {
+ }
+
+ ~PulseSequence()
+ {
+ delete gaussian;
+ delete empty;
+ }
+
+ signalVector *gaussian;
+ signalVector *empty;
+};
+
CorrelationSequence *gMidambles[] = {NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL};
CorrelationSequence *gRACHSequence = NULL;
+PulseSequence *GSMPulse = NULL;
void sigProcLibDestroy(void) {
if (GMSKRotation) {
@@ -234,6 +253,7 @@
{
initTrigTables();
initGMSKRotationTables(sps);
+ generateGSMPulse(sps, 2);
}
void GMSKRotate(signalVector &x) {
@@ -439,25 +459,36 @@
}
-signalVector* generateGSMPulse(int sps, int symbolLength)
+void generateGSMPulse(int sps, int symbolLength)
{
+ int len;
+ float arg, center;
- int numSamples = sps * symbolLength + 1;
- signalVector *x = new signalVector(numSamples);
- signalVector::iterator xP = x->begin();
- int centerPoint = (numSamples-1)/2;
- for (int i = 0; i < numSamples; i++) {
- float arg = (float) (i - centerPoint) / (float) sps;
- *xP++ = 0.96*exp(-1.1380*arg*arg-0.527*arg*arg*arg*arg); // GSM pulse approx.
+ delete GSMPulse;
+
+ /* Store a single tap filter used for correlation sequence generation */
+ GSMPulse = new PulseSequence();
+ GSMPulse->empty = new signalVector(1);
+ GSMPulse->empty->isRealOnly(true);
+ *(GSMPulse->empty->begin()) = 1.0f;
+
+ /* GSM pulse approximation */
+ GSMPulse->gaussian = new signalVector(len);
+ GSMPulse->gaussian->isRealOnly(true);
+ signalVector::iterator xP = GSMPulse->gaussian->begin();
+
+ center = (float) (len - 1.0) / 2.0;
+
+ for (int i = 0; i < len; i++) {
+ arg = ((float) i - center) / (float) sps;
+ *xP++ = 0.96 * exp(-1.1380 * arg * arg -
+ 0.527 * arg * arg * arg * arg);
}
- float avgAbsval = sqrtf(vectorNorm2(*x) / sps);
- xP = x->begin();
- for (int i = 0; i < numSamples; i++)
+ float avgAbsval = sqrtf(vectorNorm2(*GSMPulse->gaussian)/sps);
+ xP = GSMPulse->gaussian->begin();
+ for (int i = 0; i < len; i++)
*xP++ /= avgAbsval;
- x->isRealOnly(true);
- x->setSymmetry(ABSSYM);
- return x;
}
signalVector* frequencyShift(signalVector *y,
@@ -564,36 +595,22 @@
return true;
}
-signalVector *modulateBurst(const BitVector &wBurst,
- const signalVector &gsmPulse,
- int guardPeriodLength,
- int sps)
+signalVector *modulateBurst(const BitVector &wBurst, int guardPeriodLength,
+ int sps, bool emptyPulse)
{
+ int burstLen;
+ signalVector *pulse, modBurst;
+ signalVector::iterator modBurstItr;
- //static complex staticBurst[157];
+ if (emptyPulse)
+ pulse = GSMPulse->empty;
+ else
+ pulse = GSMPulse->gaussian;
- int burstSize = sps * (wBurst.size() + guardPeriodLength);
- //signalVector modBurst((complex *) staticBurst,0,burstSize);
- signalVector modBurst(burstSize);// = new signalVector(burstSize);
- modBurst.isRealOnly(true);
- //memset(staticBurst,0,sizeof(complex)*burstSize);
- modBurst.fill(0.0);
- signalVector::iterator modBurstItr = modBurst.begin();
+ burstLen = sps * (wBurst.size() + guardPeriodLength);
+ modBurst = signalVector(burstLen);
+ modBurstItr = modBurst.begin();
-#if 0
- // if wBurst is already differentially decoded
- *modBurstItr = 2.0*(wBurst[0] & 0x01)-1.0;
- signalVector::iterator prevVal = modBurstItr;
- for (unsigned int i = 1; i < wBurst.size(); i++) {
- modBurstItr += sps;
- if (wBurst[i] & 0x01)
- *modBurstItr = *prevVal * complex(0.0,1.0);
- else
- *modBurstItr = *prevVal * complex(0.0,-1.0);
- prevVal = modBurstItr;
- }
-#else
- // if wBurst are the raw bits
for (unsigned int i = 0; i < wBurst.size(); i++) {
*modBurstItr = 2.0*(wBurst[i] & 0x01)-1.0;
modBurstItr += sps;
@@ -602,16 +619,13 @@
// shift up pi/2
// ignore starting phase, since spec allows for discontinuous phase
GMSKRotate(modBurst);
-#endif
+
modBurst.isRealOnly(false);
// filter w/ pulse shape
- signalVector *shapedBurst = convolve(&modBurst,&gsmPulse,NULL,NO_DELAY);
+ signalVector *shapedBurst = convolve(&modBurst, pulse, NULL, NO_DELAY);
- //delete modBurst;
-
return shapedBurst;
-
}
float sinc(float x)
@@ -837,11 +851,8 @@
}
}
-bool generateMidamble(signalVector &gsmPulse,
- int sps,
- int TSC)
+bool generateMidamble(int sps, int TSC)
{
-
if ((TSC < 0) || (TSC > 7))
return false;
@@ -850,18 +861,13 @@
if (gMidambles[TSC]->sequenceReversedConjugated!=NULL) delete gMidambles[TSC]->sequenceReversedConjugated;
}
- signalVector emptyPulse(1);
- *(emptyPulse.begin()) = 1.0;
-
// only use middle 16 bits of each TSC
signalVector *middleMidamble = modulateBurst(gTrainingSequence[TSC].segment(5,16),
- emptyPulse,
0,
- sps);
+ sps, true);
signalVector *midamble = modulateBurst(gTrainingSequence[TSC],
- gsmPulse,
0,
- sps);
+ sps, false);
if (midamble == NULL) return false;
if (middleMidamble == NULL) return false;
@@ -895,17 +901,14 @@
return true;
}
-bool generateRACHSequence(signalVector &gsmPulse,
- int sps)
+bool generateRACHSequence(int sps)
{
-
if (gRACHSequence) {
if (gRACHSequence->sequence!=NULL) delete gRACHSequence->sequence;
if (gRACHSequence->sequenceReversedConjugated!=NULL) delete gRACHSequence->sequenceReversedConjugated;
}
signalVector *RACHSeq = modulateBurst(gRACHSynchSequence,
- gsmPulse,
0,
sps);
@@ -1136,12 +1139,8 @@
}
-SoftVector *demodulateBurst(signalVector &rxBurst,
- const signalVector &gsmPulse,
- int sps,
- complex channel,
- float TOA)
-
+SoftVector *demodulateBurst(signalVector &rxBurst, int sps,
+ complex channel, float TOA)
{
scaleVector(rxBurst,((complex) 1.0)/channel);
delayVector(rxBurst,-TOA);