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Transceiver52M: Make GSM pulse filter internal to implementation

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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>

git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6728 19bc5d8c-e614-43d4-8b26-e1612bc8e597
This commit is contained in:
Thomas Tsou
2013-10-17 06:17:53 +00:00
parent ecc81ab384
commit 20e44cb379
4 changed files with 114 additions and 116 deletions
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131
Transceiver52M/sigProcLib.cpp
View File

@@ -56,8 +56,27 @@ typedef struct {
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) {
@@ -232,6 +251,7 @@ void sigProcLibSetup(int sps)
{
initTrigTables();
initGMSKRotationTables(sps);
generateGSMPulse(sps, 2);
}
void GMSKRotate(signalVector &x) {
@@ -437,25 +457,36 @@ signalVector* convolve(const signalVector *a,
}
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,
@@ -562,36 +593,22 @@ bool vectorSlicer(signalVector *x)
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;
@@ -600,16 +617,13 @@ signalVector *modulateBurst(const BitVector &wBurst,
// 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)
@@ -835,11 +849,8 @@ void offsetVector(signalVector &x,
}
}
bool generateMidamble(signalVector &gsmPulse,
int sps,
int TSC)
bool generateMidamble(int sps, int TSC)
{
if ((TSC < 0) || (TSC > 7))
return false;
@@ -848,18 +859,13 @@ bool generateMidamble(signalVector &gsmPulse,
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;
@@ -893,17 +899,14 @@ bool generateMidamble(signalVector &gsmPulse,
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);
@@ -1134,12 +1137,8 @@ signalVector *decimateVector(signalVector &wVector,
}
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);