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osmo-trx/Transceiver52M/sigProcLib.cpp

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/*
* Copyright 2008, 2011 Free Software Foundation, Inc.
*
* This software is distributed under the terms of the GNU Affero Public License.
* See the COPYING file in the main directory for details.
*
* This use of this software may be subject to additional restrictions.
* See the LEGAL file in the main directory for details.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "sigProcLib.h"
#include "GSMCommon.h"
#include "sendLPF_961.h"
#include "rcvLPF_651.h"
using namespace GSM;
extern "C" {
#include "convolve.h"
}
#define TABLESIZE 1024
/** Lookup tables for trigonometric approximation */
float cosTable[TABLESIZE+1]; // add 1 element for wrap around
float sinTable[TABLESIZE+1];
/** Constants */
static const float M_PI_F = (float)M_PI;
static const float M_2PI_F = (float)(2.0*M_PI);
static const float M_1_2PI_F = 1/M_2PI_F;
/** Static vectors that contain a precomputed +/- f_b/4 sinusoid */
signalVector *GMSKRotation = NULL;
signalVector *GMSKReverseRotation = NULL;
/*
* RACH and midamble correlation waveforms. Store the buffer separately
* because we need to allocate it explicitly outside of the signal vector
* constructor. This is because C++ (prior to C++11) is unable to natively
* perform 16-byte memory alignment required by many SSE instructions.
*/
struct CorrelationSequence {
CorrelationSequence() : sequence(NULL), buffer(NULL)
{
}
~CorrelationSequence()
{
delete sequence;
free(buffer);
}
signalVector *sequence;
void *buffer;
float TOA;
complex gain;
};
/*
* Gaussian and empty modulation pulses. Like the correlation sequences,
* store the runtime (Gaussian) buffer separately because of needed alignment
* for SSE instructions.
*/
struct PulseSequence {
PulseSequence() : gaussian(NULL), empty(NULL), buffer(NULL)
{
}
~PulseSequence()
{
delete gaussian;
delete empty;
free(buffer);
}
signalVector *gaussian;
signalVector *empty;
void *buffer;
};
CorrelationSequence *gMidambles[] = {NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL};
CorrelationSequence *gRACHSequence = NULL;
PulseSequence *GSMPulse = NULL;
void sigProcLibDestroy()
{
for (int i = 0; i < 8; i++) {
delete gMidambles[i];
gMidambles[i] = NULL;
}
delete GMSKRotation;
delete GMSKReverseRotation;
delete gRACHSequence;
delete GSMPulse;
GMSKRotation = NULL;
GMSKReverseRotation = NULL;
gRACHSequence = NULL;
GSMPulse = NULL;
}
// dB relative to 1.0.
// if > 1.0, then return 0 dB
float dB(float x) {
float arg = 1.0F;
float dB = 0.0F;
if (x >= 1.0F) return 0.0F;
if (x <= 0.0F) return -200.0F;
float prevArg = arg;
float prevdB = dB;
float stepSize = 16.0F;
float dBstepSize = 12.0F;
while (stepSize > 1.0F) {
do {
prevArg = arg;
prevdB = dB;
arg /= stepSize;
dB -= dBstepSize;
} while (arg > x);
arg = prevArg;
dB = prevdB;
stepSize *= 0.5F;
dBstepSize -= 3.0F;
}
return ((arg-x)*(dB-3.0F) + (x-arg*0.5F)*dB)/(arg - arg*0.5F);
}
// 10^(-dB/10), inverse of dB func.
float dBinv(float x) {
float arg = 1.0F;
float dB = 0.0F;
if (x >= 0.0F) return 1.0F;
if (x <= -200.0F) return 0.0F;
float prevArg = arg;
float prevdB = dB;
float stepSize = 16.0F;
float dBstepSize = 12.0F;
while (stepSize > 1.0F) {
do {
prevArg = arg;
prevdB = dB;
arg /= stepSize;
dB -= dBstepSize;
} while (dB > x);
arg = prevArg;
dB = prevdB;
stepSize *= 0.5F;
dBstepSize -= 3.0F;
}
return ((dB-x)*(arg*0.5F)+(x-(dB-3.0F))*(arg))/3.0F;
}
float vectorNorm2(const signalVector &x)
{
signalVector::const_iterator xPtr = x.begin();
float Energy = 0.0;
for (;xPtr != x.end();xPtr++) {
Energy += xPtr->norm2();
}
return Energy;
}
float vectorPower(const signalVector &x)
{
return vectorNorm2(x)/x.size();
}
/** compute cosine via lookup table */
float cosLookup(const float x)
{
float arg = x*M_1_2PI_F;
while (arg > 1.0F) arg -= 1.0F;
while (arg < 0.0F) arg += 1.0F;
const float argT = arg*((float)TABLESIZE);
const int argI = (int)argT;
const float delta = argT-argI;
const float iDelta = 1.0F-delta;
return iDelta*cosTable[argI] + delta*cosTable[argI+1];
}
/** compute sine via lookup table */
float sinLookup(const float x)
{
float arg = x*M_1_2PI_F;
while (arg > 1.0F) arg -= 1.0F;
while (arg < 0.0F) arg += 1.0F;
const float argT = arg*((float)TABLESIZE);
const int argI = (int)argT;
const float delta = argT-argI;
const float iDelta = 1.0F-delta;
return iDelta*sinTable[argI] + delta*sinTable[argI+1];
}
/** compute e^(-jx) via lookup table. */
complex expjLookup(float x)
{
float arg = x*M_1_2PI_F;
while (arg > 1.0F) arg -= 1.0F;
while (arg < 0.0F) arg += 1.0F;
const float argT = arg*((float)TABLESIZE);
const int argI = (int)argT;
const float delta = argT-argI;
const float iDelta = 1.0F-delta;
return complex(iDelta*cosTable[argI] + delta*cosTable[argI+1],
iDelta*sinTable[argI] + delta*sinTable[argI+1]);
}
/** Library setup functions */
void initTrigTables() {
for (int i = 0; i < TABLESIZE+1; i++) {
cosTable[i] = cos(2.0*M_PI*i/TABLESIZE);
sinTable[i] = sin(2.0*M_PI*i/TABLESIZE);
}
}
void initGMSKRotationTables(int sps)
{
GMSKRotation = new signalVector(157 * sps);
GMSKReverseRotation = new signalVector(157 * sps);
signalVector::iterator rotPtr = GMSKRotation->begin();
signalVector::iterator revPtr = GMSKReverseRotation->begin();
float phase = 0.0;
while (rotPtr != GMSKRotation->end()) {
*rotPtr++ = expjLookup(phase);
*revPtr++ = expjLookup(-phase);
phase += M_PI_F / 2.0F / (float) sps;
}
}
bool sigProcLibSetup(int sps)
{
if ((sps != 1) && (sps != 2) && (sps != 4))
return false;
initTrigTables();
initGMSKRotationTables(sps);
generateGSMPulse(sps, 2);
if (!generateRACHSequence(sps)) {
sigProcLibDestroy();
return false;
}
return true;
}
void GMSKRotate(signalVector &x) {
signalVector::iterator xPtr = x.begin();
signalVector::iterator rotPtr = GMSKRotation->begin();
if (x.isRealOnly()) {
while (xPtr < x.end()) {
*xPtr = *rotPtr++ * (xPtr->real());
xPtr++;
}
}
else {
while (xPtr < x.end()) {
*xPtr = *rotPtr++ * (*xPtr);
xPtr++;
}
}
}
void GMSKReverseRotate(signalVector &x) {
signalVector::iterator xPtr= x.begin();
signalVector::iterator rotPtr = GMSKReverseRotation->begin();
if (x.isRealOnly()) {
while (xPtr < x.end()) {
*xPtr = *rotPtr++ * (xPtr->real());
xPtr++;
}
}
else {
while (xPtr < x.end()) {
*xPtr = *rotPtr++ * (*xPtr);
xPtr++;
}
}
}
signalVector *convolve(const signalVector *x,
const signalVector *h,
signalVector *y,
ConvType spanType, int start,
unsigned len, unsigned step, int offset)
{
int rc, head = 0, tail = 0;
bool alloc = false, append = false;
const signalVector *_x = NULL;
if (!x || !h)
return NULL;
switch (spanType) {
case START_ONLY:
start = 0;
head = h->size();
len = x->size();
append = true;
break;
case NO_DELAY:
start = h->size() / 2;
head = start;
tail = start;
len = x->size();
append = true;
break;
case CUSTOM:
if (start < h->size() - 1) {
head = h->size() - start;
append = true;
}
if (start + len > x->size()) {
tail = start + len - x->size();
append = true;
}
break;
default:
return NULL;
}
/*
* Error if the output vector is too small. Create the output vector
* if the pointer is NULL.
*/
if (y && (len > y->size()))
return NULL;
if (!y) {
y = new signalVector(len);
alloc = true;
}
/* Prepend or post-pend the input vector if the parameters require it */
if (append)
_x = new signalVector(*x, head, tail);
else
_x = x;
/*
* Four convovle types:
* 1. Complex-Real (aligned)
* 2. Complex-Complex (aligned)
* 3. Complex-Real (!aligned)
* 4. Complex-Complex (!aligned)
*/
if (h->isRealOnly() && h->isAligned()) {
rc = convolve_real((float *) _x->begin(), _x->size(),
(float *) h->begin(), h->size(),
(float *) y->begin(), y->size(),
start, len, step, offset);
} else if (!h->isRealOnly() && h->isAligned()) {
rc = convolve_complex((float *) _x->begin(), _x->size(),
(float *) h->begin(), h->size(),
(float *) y->begin(), y->size(),
start, len, step, offset);
} else if (h->isRealOnly() && !h->isAligned()) {
rc = base_convolve_real((float *) _x->begin(), _x->size(),
(float *) h->begin(), h->size(),
(float *) y->begin(), y->size(),
start, len, step, offset);
} else if (!h->isRealOnly() && !h->isAligned()) {
rc = base_convolve_complex((float *) _x->begin(), _x->size(),
(float *) h->begin(), h->size(),
(float *) y->begin(), y->size(),
start, len, step, offset);
} else {
rc = -1;
}
if (append)
delete _x;
if (rc < 0) {
if (alloc)
delete y;
return NULL;
}
return y;
}
void generateGSMPulse(int sps, int symbolLength)
{
int len;
float arg, center;
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;
len = sps * symbolLength;
if (len < 4)
len = 4;
/* GSM pulse approximation */
GSMPulse->buffer = convolve_h_alloc(len);
GSMPulse->gaussian = new signalVector((complex *)
GSMPulse->buffer, 0, len);
GSMPulse->gaussian->setAligned(true);
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(*GSMPulse->gaussian)/sps);
xP = GSMPulse->gaussian->begin();
for (int i = 0; i < len; i++)
*xP++ /= avgAbsval;
}
signalVector* frequencyShift(signalVector *y,
signalVector *x,
float freq,
float startPhase,
float *finalPhase)
{
if (!x) return NULL;
if (y==NULL) {
y = new signalVector(x->size());
y->isRealOnly(x->isRealOnly());
if (y==NULL) return NULL;
}
if (y->size() < x->size()) return NULL;
float phase = startPhase;
signalVector::iterator yP = y->begin();
signalVector::iterator xPEnd = x->end();
signalVector::iterator xP = x->begin();
if (x->isRealOnly()) {
while (xP < xPEnd) {
(*yP++) = expjLookup(phase)*( (xP++)->real() );
phase += freq;
}
}
else {
while (xP < xPEnd) {
(*yP++) = (*xP++)*expjLookup(phase);
phase += freq;
}
}
if (finalPhase) *finalPhase = phase;
return y;
}
signalVector* reverseConjugate(signalVector *b)
{
signalVector *tmp = new signalVector(b->size());
tmp->isRealOnly(b->isRealOnly());
signalVector::iterator bP = b->begin();
signalVector::iterator bPEnd = b->end();
signalVector::iterator tmpP = tmp->end()-1;
if (!b->isRealOnly()) {
while (bP < bPEnd) {
*tmpP-- = bP->conj();
bP++;
}
}
else {
while (bP < bPEnd) {
*tmpP-- = bP->real();
bP++;
}
}
return tmp;
}
/* soft output slicer */
bool vectorSlicer(signalVector *x)
{
signalVector::iterator xP = x->begin();
signalVector::iterator xPEnd = x->end();
while (xP < xPEnd) {
*xP = (complex) (0.5*(xP->real()+1.0F));
if (xP->real() > 1.0) *xP = 1.0;
if (xP->real() < 0.0) *xP = 0.0;
xP++;
}
return true;
}
/* Assume input bits are not differentially encoded */
signalVector *modulateBurst(const BitVector &wBurst, int guardPeriodLength,
int sps, bool emptyPulse)
{
int burstLen;
signalVector *pulse, *shapedBurst, modBurst;
signalVector::iterator modBurstItr;
if (emptyPulse)
pulse = GSMPulse->empty;
else
pulse = GSMPulse->gaussian;
burstLen = sps * (wBurst.size() + guardPeriodLength);
modBurst = signalVector(burstLen);
modBurstItr = modBurst.begin();
for (unsigned int i = 0; i < wBurst.size(); i++) {
*modBurstItr = 2.0*(wBurst[i] & 0x01)-1.0;
modBurstItr += sps;
}
// shift up pi/2
// ignore starting phase, since spec allows for discontinuous phase
GMSKRotate(modBurst);
modBurst.isRealOnly(false);
// filter w/ pulse shape
shapedBurst = convolve(&modBurst, pulse, NULL, START_ONLY);
if (!shapedBurst)
return NULL;
return shapedBurst;
}
float sinc(float x)
{
if ((x >= 0.01F) || (x <= -0.01F)) return (sinLookup(x)/x);
return 1.0F;
}
bool delayVector(signalVector &wBurst, float delay)
{
int intOffset = (int) floor(delay);
float fracOffset = delay - intOffset;
// do fractional shift first, only do it for reasonable offsets
if (fabs(fracOffset) > 1e-2) {
// create sinc function
signalVector sincVector(21);
sincVector.isRealOnly(true);
signalVector::iterator sincBurstItr = sincVector.end();
for (int i = 0; i < 21; i++)
*--sincBurstItr = (complex) sinc(M_PI_F*(i-10-fracOffset));
signalVector shiftedBurst(wBurst.size());
if (!convolve(&wBurst, &sincVector, &shiftedBurst, NO_DELAY))
return false;
wBurst.clone(shiftedBurst);
}
if (intOffset < 0) {
intOffset = -intOffset;
signalVector::iterator wBurstItr = wBurst.begin();
signalVector::iterator shiftedItr = wBurst.begin()+intOffset;
while (shiftedItr < wBurst.end())
*wBurstItr++ = *shiftedItr++;
while (wBurstItr < wBurst.end())
*wBurstItr++ = 0.0;
}
else {
signalVector::iterator wBurstItr = wBurst.end()-1;
signalVector::iterator shiftedItr = wBurst.end()-1-intOffset;
while (shiftedItr >= wBurst.begin())
*wBurstItr-- = *shiftedItr--;
while (wBurstItr >= wBurst.begin())
*wBurstItr-- = 0.0;
}
}
signalVector *gaussianNoise(int length,
float variance,
complex mean)
{
signalVector *noise = new signalVector(length);
signalVector::iterator nPtr = noise->begin();
float stddev = sqrtf(variance);
while (nPtr < noise->end()) {
float u1 = (float) rand()/ (float) RAND_MAX;
while (u1==0.0)
u1 = (float) rand()/ (float) RAND_MAX;
float u2 = (float) rand()/ (float) RAND_MAX;
float arg = 2.0*M_PI*u2;
*nPtr = mean + stddev*complex(cos(arg),sin(arg))*sqrtf(-2.0*log(u1));
nPtr++;
}
return noise;
}
complex interpolatePoint(const signalVector &inSig,
float ix)
{
int start = (int) (floor(ix) - 10);
if (start < 0) start = 0;
int end = (int) (floor(ix) + 11);
if ((unsigned) end > inSig.size()-1) end = inSig.size()-1;
complex pVal = 0.0;
if (!inSig.isRealOnly()) {
for (int i = start; i < end; i++)
pVal += inSig[i] * sinc(M_PI_F*(i-ix));
}
else {
for (int i = start; i < end; i++)
pVal += inSig[i].real() * sinc(M_PI_F*(i-ix));
}
return pVal;
}
complex peakDetect(const signalVector &rxBurst,
float *peakIndex,
float *avgPwr)
{
complex maxVal = 0.0;
float maxIndex = -1;
float sumPower = 0.0;
for (unsigned int i = 0; i < rxBurst.size(); i++) {
float samplePower = rxBurst[i].norm2();
if (samplePower > maxVal.real()) {
maxVal = samplePower;
maxIndex = i;
}
sumPower += samplePower;
}
// interpolate around the peak
// to save computation, we'll use early-late balancing
float earlyIndex = maxIndex-1;
float lateIndex = maxIndex+1;
float incr = 0.5;
while (incr > 1.0/1024.0) {
complex earlyP = interpolatePoint(rxBurst,earlyIndex);
complex lateP = interpolatePoint(rxBurst,lateIndex);
if (earlyP < lateP)
earlyIndex += incr;
else if (earlyP > lateP)
earlyIndex -= incr;
else break;
incr /= 2.0;
lateIndex = earlyIndex + 2.0;
}
maxIndex = earlyIndex + 1.0;
maxVal = interpolatePoint(rxBurst,maxIndex);
if (peakIndex!=NULL)
*peakIndex = maxIndex;
if (avgPwr!=NULL)
*avgPwr = (sumPower-maxVal.norm2()) / (rxBurst.size()-1);
return maxVal;
}
void scaleVector(signalVector &x,
complex scale)
{
signalVector::iterator xP = x.begin();
signalVector::iterator xPEnd = x.end();
if (!x.isRealOnly()) {
while (xP < xPEnd) {
*xP = *xP * scale;
xP++;
}
}
else {
while (xP < xPEnd) {
*xP = xP->real() * scale;
xP++;
}
}
}
/** in-place conjugation */
void conjugateVector(signalVector &x)
{
if (x.isRealOnly()) return;
signalVector::iterator xP = x.begin();
signalVector::iterator xPEnd = x.end();
while (xP < xPEnd) {
*xP = xP->conj();
xP++;
}
}
// in-place addition!!
bool addVector(signalVector &x,
signalVector &y)
{
signalVector::iterator xP = x.begin();
signalVector::iterator yP = y.begin();
signalVector::iterator xPEnd = x.end();
signalVector::iterator yPEnd = y.end();
while ((xP < xPEnd) && (yP < yPEnd)) {
*xP = *xP + *yP;
xP++; yP++;
}
return true;
}
// in-place multiplication!!
bool multVector(signalVector &x,
signalVector &y)
{
signalVector::iterator xP = x.begin();
signalVector::iterator yP = y.begin();
signalVector::iterator xPEnd = x.end();
signalVector::iterator yPEnd = y.end();
while ((xP < xPEnd) && (yP < yPEnd)) {
*xP = (*xP) * (*yP);
xP++; yP++;
}
return true;
}
void offsetVector(signalVector &x,
complex offset)
{
signalVector::iterator xP = x.begin();
signalVector::iterator xPEnd = x.end();
if (!x.isRealOnly()) {
while (xP < xPEnd) {
*xP += offset;
xP++;
}
}
else {
while (xP < xPEnd) {
*xP = xP->real() + offset;
xP++;
}
}
}
bool generateMidamble(int sps, int tsc)
{
bool status = true;
complex *data = NULL;
signalVector *autocorr = NULL, *midamble = NULL;
signalVector *midMidamble = NULL, *_midMidamble = NULL;
if ((tsc < 0) || (tsc > 7))
return false;
delete gMidambles[tsc];
/* Use middle 16 bits of each TSC. Correlation sequence is not pulse shaped */
midMidamble = modulateBurst(gTrainingSequence[tsc].segment(5,16), 0, sps, true);
if (!midMidamble)
return false;
/* Simulated receive sequence is pulse shaped */
midamble = modulateBurst(gTrainingSequence[tsc], 0, sps, false);
if (!midamble) {
status = false;
goto release;
}
// NOTE: Because ideal TSC 16-bit midamble is 66 symbols into burst,
// the ideal TSC has an + 180 degree phase shift,
// due to the pi/2 frequency shift, that
// needs to be accounted for.
// 26-midamble is 61 symbols into burst, has +90 degree phase shift.
scaleVector(*midMidamble, complex(-1.0, 0.0));
scaleVector(*midamble, complex(0.0, 1.0));
conjugateVector(*midMidamble);
/* For SSE alignment, reallocate the midamble sequence on 16-byte boundary */
data = (complex *) convolve_h_alloc(midMidamble->size());
_midMidamble = new signalVector(data, 0, midMidamble->size());
_midMidamble->setAligned(true);
memcpy(_midMidamble->begin(), midMidamble->begin(),
midMidamble->size() * sizeof(complex));
autocorr = convolve(midamble, _midMidamble, NULL, NO_DELAY);
if (!autocorr) {
status = false;
goto release;
}
gMidambles[tsc] = new CorrelationSequence;
gMidambles[tsc]->buffer = data;
gMidambles[tsc]->sequence = _midMidamble;
gMidambles[tsc]->gain = peakDetect(*autocorr,&gMidambles[tsc]->TOA, NULL);
release:
delete autocorr;
delete midamble;
delete midMidamble;
if (!status) {
delete _midMidamble;
free(data);
gMidambles[tsc] = NULL;
}
return status;
}
bool generateRACHSequence(int sps)
{
bool status = true;
complex *data = NULL;
signalVector *autocorr = NULL;
signalVector *seq0 = NULL, *seq1 = NULL, *_seq1 = NULL;
delete gRACHSequence;
seq0 = modulateBurst(gRACHSynchSequence, 0, sps, false);
if (!seq0)
return false;
seq1 = modulateBurst(gRACHSynchSequence.segment(0, 40), 0, sps, true);
if (!seq1) {
status = false;
goto release;
}
conjugateVector(*seq1);
/* For SSE alignment, reallocate the midamble sequence on 16-byte boundary */
data = (complex *) convolve_h_alloc(seq1->size());
_seq1 = new signalVector(data, 0, seq1->size());
_seq1->setAligned(true);
memcpy(_seq1->begin(), seq1->begin(), seq1->size() * sizeof(complex));
autocorr = convolve(seq0, _seq1, autocorr, NO_DELAY);
if (!autocorr) {
status = false;
goto release;
}
gRACHSequence = new CorrelationSequence;
gRACHSequence->sequence = _seq1;
gRACHSequence->buffer = data;
gRACHSequence->gain = peakDetect(*autocorr,&gRACHSequence->TOA, NULL);
release:
delete autocorr;
delete seq0;
delete seq1;
if (!status) {
delete _seq1;
free(data);
gRACHSequence = NULL;
}
return status;
}
int detectRACHBurst(signalVector &rxBurst,
float thresh,
int sps,
complex *amp,
float *toa)
{
int start, len, num = 0;
float _toa, rms, par, avg = 0.0f;
complex _amp, *peak;
signalVector corr, *sync = gRACHSequence->sequence;
if ((sps != 1) && (sps != 2) && (sps != 4))
return -1;
start = 40 * sps;
len = 24 * sps;
corr = signalVector(len);
if (!convolve(&rxBurst, sync, &corr,
CUSTOM, start, len, sps, 0)) {
return -1;
}
_amp = peakDetect(corr, &_toa, NULL);
if ((_toa < 3) || (_toa > len - 3))
goto notfound;
peak = corr.begin() + (int) rint(_toa);
for (int i = 2 * sps; i <= 5 * sps; i++) {
if (peak - i >= corr.begin()) {
avg += (peak - i)->norm2();
num++;
}
if (peak + i < corr.end()) {
avg += (peak + i)->norm2();
num++;
}
}
if (num < 2)
goto notfound;
rms = sqrtf(avg / (float) num) + 0.00001;
par = _amp.abs() / rms;
if (par < thresh)
goto notfound;
/* Subtract forward tail bits from delay */
if (toa)
*toa = _toa - 8 * sps;
if (amp)
*amp = _amp / gRACHSequence->gain;
return 1;
notfound:
if (amp)
*amp = 0.0f;
if (toa)
*toa = 0.0f;
return 0;
}
bool energyDetect(signalVector &rxBurst,
unsigned windowLength,
float detectThreshold,
float *avgPwr)
{
signalVector::const_iterator windowItr = rxBurst.begin(); //+rxBurst.size()/2 - 5*windowLength/2;
float energy = 0.0;
if (windowLength < 0) windowLength = 20;
if (windowLength > rxBurst.size()) windowLength = rxBurst.size();
for (unsigned i = 0; i < windowLength; i++) {
energy += windowItr->norm2();
windowItr+=4;
}
if (avgPwr) *avgPwr = energy/windowLength;
return (energy/windowLength > detectThreshold*detectThreshold);
}
int analyzeTrafficBurst(signalVector &rxBurst, unsigned tsc, float thresh,
int sps, complex *amp, float *toa, unsigned max_toa,
bool chan_req, signalVector **chan, float *chan_offset)
{
int start, target, len, num = 0;
complex _amp, *peak;
float _toa, rms, par, avg = 0.0f;
signalVector corr, *sync, *_chan;
if ((tsc < 0) || (tsc > 7) || ((sps != 1) && (sps != 2) && (sps != 4)))
return -1;
target = 3 + 58 + 5 + 16;
start = (target - 8) * sps;
len = (8 + 8 + max_toa) * sps;
sync = gMidambles[tsc]->sequence;
sync = gMidambles[tsc]->sequence;
corr = signalVector(len);
if (!convolve(&rxBurst, sync, &corr,
CUSTOM, start, len, sps, 0)) {
return -1;
}
_amp = peakDetect(corr, &_toa, NULL);
peak = corr.begin() + (int) rint(_toa);
/* Check for bogus results */
if ((_toa < 0.0) || (_toa > corr.size()))
goto notfound;
for (int i = 2 * sps; i <= 5 * sps; i++) {
if (peak - i >= corr.begin()) {
avg += (peak - i)->norm2();
num++;
}
if (peak + i < corr.end()) {
avg += (peak + i)->norm2();
num++;
}
}
if (num < 2)
goto notfound;
rms = sqrtf(avg / (float) num) + 0.00001;
par = (_amp.abs()) / rms;
if (par < thresh)
goto notfound;
/*
* NOTE: Because ideal TSC is 66 symbols into burst,
* the ideal TSC has an +/- 180 degree phase shift,
* due to the pi/4 frequency shift, that
* needs to be accounted for.
*/
if (amp)
*amp = _amp / gMidambles[tsc]->gain;
/* Delay one half of peak-centred correlation length */
_toa -= sps * 8;
if (toa)
*toa = _toa;
if (chan_req) {
_chan = new signalVector(6 * sps);
delayVector(corr, -_toa);
corr.segmentCopyTo(*_chan, target - 3, _chan->size());
scaleVector(*_chan, complex(1.0, 0.0) / gMidambles[tsc]->gain);
*chan = _chan;
if (chan_offset)
*chan_offset = 3.0 * sps;;
}
return 1;
notfound:
if (amp)
*amp = 0.0f;
if (toa)
*toa = 0.0f;
return 0;
}
signalVector *decimateVector(signalVector &wVector,
int decimationFactor)
{
if (decimationFactor <= 1) return NULL;
signalVector *decVector = new signalVector(wVector.size()/decimationFactor);
decVector->isRealOnly(wVector.isRealOnly());
signalVector::iterator vecItr = decVector->begin();
for (unsigned int i = 0; i < wVector.size();i+=decimationFactor)
*vecItr++ = wVector[i];
return decVector;
}
SoftVector *demodulateBurst(signalVector &rxBurst, int sps,
complex channel, float TOA)
{
scaleVector(rxBurst,((complex) 1.0)/channel);
delayVector(rxBurst,-TOA);
signalVector *shapedBurst = &rxBurst;
// shift up by a quarter of a frequency
// ignore starting phase, since spec allows for discontinuous phase
GMSKReverseRotate(*shapedBurst);
// run through slicer
if (sps > 1) {
signalVector *decShapedBurst = decimateVector(*shapedBurst, sps);
shapedBurst = decShapedBurst;
}
vectorSlicer(shapedBurst);
SoftVector *burstBits = new SoftVector(shapedBurst->size());
SoftVector::iterator burstItr = burstBits->begin();
signalVector::iterator shapedItr = shapedBurst->begin();
for (; shapedItr < shapedBurst->end(); shapedItr++)
*burstItr++ = shapedItr->real();
if (sps > 1)
delete shapedBurst;
return burstBits;
}
// 1.0 is sampling frequency
// must satisfy cutoffFreq > 1/filterLen
signalVector *createLPF(float cutoffFreq,
int filterLen,
float gainDC)
{
#if 0
signalVector *LPF = new signalVector(filterLen-1);
LPF->isRealOnly(true);
LPF->setSymmetry(ABSSYM);
signalVector::iterator itr = LPF->begin();
double sum = 0.0;
for (int i = 1; i < filterLen; i++) {
float ys = sinc(M_2PI_F*cutoffFreq*((float)i-(float)(filterLen)/2.0F));
float yg = 4.0F * cutoffFreq;
// Blackman -- less brickwall (sloping transition) but larger stopband attenuation
float yw = 0.42 - 0.5*cos(((float)i)*M_2PI_F/(float)(filterLen)) + 0.08*cos(((float)i)*2*M_2PI_F/(float)(filterLen));
// Hamming -- more brickwall with smaller stopband attenuation
//float yw = 0.53836F - 0.46164F * cos(((float)i)*M_2PI_F/(float)(filterLen+1));
*itr++ = (complex) ys*yg*yw;
sum += ys*yg*yw;
}
#else
double sum = 0.0;
signalVector *LPF;
signalVector::iterator itr;
if (filterLen == 651) { // receive LPF
LPF = new signalVector(651);
LPF->isRealOnly(true);
itr = LPF->begin();
for (int i = 0; i < filterLen; i++) {
*itr++ = complex(rcvLPF_651[i],0.0);
sum += rcvLPF_651[i];
}
}
else {
LPF = new signalVector(961);
LPF->isRealOnly(true);
itr = LPF->begin();
for (int i = 0; i < filterLen; i++) {
*itr++ = complex(sendLPF_961[i],0.0);
sum += sendLPF_961[i];
}
}
#endif
float normFactor = gainDC/sum; //sqrtf(gainDC/vectorNorm2(*LPF));
// normalize power
itr = LPF->begin();
for (int i = 0; i < filterLen; i++) {
*itr = *itr*normFactor;
itr++;
}
return LPF;
}
#define POLYPHASESPAN 10
// assumes filter group delay is 0.5*(length of filter)
signalVector *polyphaseResampleVector(signalVector &wVector,
int P, int Q,
signalVector *LPF)
{
bool deleteLPF = false;
if (LPF==NULL) {
float cutoffFreq = (P < Q) ? (1.0/(float) Q) : (1.0/(float) P);
LPF = createLPF(cutoffFreq/3.0,100*POLYPHASESPAN+1,Q);
deleteLPF = true;
}
signalVector *resampledVector = new signalVector((int) ceil(wVector.size()*(float) P / (float) Q));
resampledVector->fill(0);
resampledVector->isRealOnly(wVector.isRealOnly());
signalVector::iterator newItr = resampledVector->begin();
//FIXME: need to update for real-only vectors
int outputIx = (LPF->size()+1)/2/Q; //((P > Q) ? P : Q);
while (newItr < resampledVector->end()) {
int outputBranch = (outputIx*Q) % P;
int inputOffset = (outputIx*Q - outputBranch)/P;
signalVector::const_iterator inputItr = wVector.begin() + inputOffset;
signalVector::const_iterator filtItr = LPF->begin() + outputBranch;
while (inputItr >= wVector.end()) {
inputItr--;
filtItr+=P;
}
complex sum = 0.0;
if ((LPF->getSymmetry()!=ABSSYM) || (P>1)) {
if (!LPF->isRealOnly()) {
while ( (inputItr >= wVector.begin()) && (filtItr < LPF->end()) ) {
sum += (*inputItr)*(*filtItr);
inputItr--;
filtItr += P;
}
}
else {
while ( (inputItr >= wVector.begin()) && (filtItr < LPF->end()) ) {
sum += (*inputItr)*(filtItr->real());
inputItr--;
filtItr += P;
}
}
}
else {
signalVector::const_iterator revInputItr = inputItr- LPF->size() + 1;
signalVector::const_iterator filtMidpoint = LPF->begin()+(LPF->size()-1)/2;
if (!LPF->isRealOnly()) {
while (filtItr <= filtMidpoint) {
if (inputItr < revInputItr) break;
if (inputItr == revInputItr)
sum += (*inputItr)*(*filtItr);
else if ( (inputItr < wVector.end()) && (revInputItr >= wVector.begin()) )
sum += (*inputItr + *revInputItr)*(*filtItr);
else if ( inputItr < wVector.end() )
sum += (*inputItr)*(*filtItr);
else if ( revInputItr >= wVector.begin() )
sum += (*revInputItr)*(*filtItr);
inputItr--;
revInputItr++;
filtItr++;
}
}
else {
while (filtItr <= filtMidpoint) {
if (inputItr < revInputItr) break;
if (inputItr == revInputItr)
sum += (*inputItr)*(filtItr->real());
else if ( (inputItr < wVector.end()) && (revInputItr >= wVector.begin()) )
sum += (*inputItr + *revInputItr)*(filtItr->real());
else if ( inputItr < wVector.end() )
sum += (*inputItr)*(filtItr->real());
else if ( revInputItr >= wVector.begin() )
sum += (*revInputItr)*(filtItr->real());
inputItr--;
revInputItr++;
filtItr++;
}
}
}
*newItr = sum;
newItr++;
outputIx++;
}
if (deleteLPF) delete LPF;
return resampledVector;
}
signalVector *resampleVector(signalVector &wVector,
float expFactor,
complex endPoint)
{
if (expFactor < 1.0) return NULL;
signalVector *retVec = new signalVector((int) ceil(wVector.size()*expFactor));
float t = 0.0;
signalVector::iterator retItr = retVec->begin();
while (retItr < retVec->end()) {
unsigned tLow = (unsigned int) floor(t);
unsigned tHigh = tLow + 1;
if (tLow > wVector.size()-1) break;
if (tHigh > wVector.size()) break;
complex lowPoint = wVector[tLow];
complex highPoint = (tHigh == wVector.size()) ? endPoint : wVector[tHigh];
complex a = (tHigh-t);
complex b = (t-tLow);
*retItr = (a*lowPoint + b*highPoint);
t += 1.0/expFactor;
}
return retVec;
}
// Assumes symbol-spaced sampling!!!
// Based upon paper by Al-Dhahir and Cioffi
bool designDFE(signalVector &channelResponse,
float SNRestimate,
int Nf,
signalVector **feedForwardFilter,
signalVector **feedbackFilter)
{
signalVector G0(Nf);
signalVector G1(Nf);
signalVector::iterator G0ptr = G0.begin();
signalVector::iterator G1ptr = G1.begin();
signalVector::iterator chanPtr = channelResponse.begin();
int nu = channelResponse.size()-1;
*G0ptr = 1.0/sqrtf(SNRestimate);
for(int j = 0; j <= nu; j++) {
*G1ptr = chanPtr->conj();
G1ptr++; chanPtr++;
}
signalVector *L[Nf];
signalVector::iterator Lptr;
float d;
for(int i = 0; i < Nf; i++) {
d = G0.begin()->norm2() + G1.begin()->norm2();
L[i] = new signalVector(Nf+nu);
Lptr = L[i]->begin()+i;
G0ptr = G0.begin(); G1ptr = G1.begin();
while ((G0ptr < G0.end()) && (Lptr < L[i]->end())) {
*Lptr = (*G0ptr*(G0.begin()->conj()) + *G1ptr*(G1.begin()->conj()) )/d;
Lptr++;
G0ptr++;
G1ptr++;
}
complex k = (*G1.begin())/(*G0.begin());
if (i != Nf-1) {
signalVector G0new = G1;
scaleVector(G0new,k.conj());
addVector(G0new,G0);
signalVector G1new = G0;
scaleVector(G1new,k*(-1.0));
addVector(G1new,G1);
delayVector(G1new,-1.0);
scaleVector(G0new,1.0/sqrtf(1.0+k.norm2()));
scaleVector(G1new,1.0/sqrtf(1.0+k.norm2()));
G0 = G0new;
G1 = G1new;
}
}
*feedbackFilter = new signalVector(nu);
L[Nf-1]->segmentCopyTo(**feedbackFilter,Nf,nu);
scaleVector(**feedbackFilter,(complex) -1.0);
conjugateVector(**feedbackFilter);
signalVector v(Nf);
signalVector::iterator vStart = v.begin();
signalVector::iterator vPtr;
*(vStart+Nf-1) = (complex) 1.0;
for(int k = Nf-2; k >= 0; k--) {
Lptr = L[k]->begin()+k+1;
vPtr = vStart + k+1;
complex v_k = 0.0;
for (int j = k+1; j < Nf; j++) {
v_k -= (*vPtr)*(*Lptr);
vPtr++; Lptr++;
}
*(vStart + k) = v_k;
}
*feedForwardFilter = new signalVector(Nf);
signalVector::iterator w = (*feedForwardFilter)->end();
for (int i = 0; i < Nf; i++) {
delete L[i];
complex w_i = 0.0;
int endPt = ( nu < (Nf-1-i) ) ? nu : (Nf-1-i);
vPtr = vStart+i;
chanPtr = channelResponse.begin();
for (int k = 0; k < endPt+1; k++) {
w_i += (*vPtr)*(chanPtr->conj());
vPtr++; chanPtr++;
}
*--w = w_i/d;
}
return true;
}
// Assumes symbol-rate sampling!!!!
SoftVector *equalizeBurst(signalVector &rxBurst,
float TOA,
int sps,
signalVector &w, // feedforward filter
signalVector &b) // feedback filter
{
signalVector *postForwardFull;
if (!delayVector(rxBurst, -TOA))
return NULL;
postForwardFull = convolve(&rxBurst, &w, NULL,
CUSTOM, 0, rxBurst.size() + w.size() - 1);
if (!postForwardFull)
return NULL;
signalVector* postForward = new signalVector(rxBurst.size());
postForwardFull->segmentCopyTo(*postForward,w.size()-1,rxBurst.size());
delete postForwardFull;
signalVector::iterator dPtr = postForward->begin();
signalVector::iterator dBackPtr;
signalVector::iterator rotPtr = GMSKRotation->begin();
signalVector::iterator revRotPtr = GMSKReverseRotation->begin();
signalVector *DFEoutput = new signalVector(postForward->size());
signalVector::iterator DFEItr = DFEoutput->begin();
// NOTE: can insert the midamble and/or use midamble to estimate BER
for (; dPtr < postForward->end(); dPtr++) {
dBackPtr = dPtr-1;
signalVector::iterator bPtr = b.begin();
while ( (bPtr < b.end()) && (dBackPtr >= postForward->begin()) ) {
*dPtr = *dPtr + (*bPtr)*(*dBackPtr);
bPtr++;
dBackPtr--;
}
*dPtr = *dPtr * (*revRotPtr);
*DFEItr = *dPtr;
// make decision on symbol
*dPtr = (dPtr->real() > 0.0) ? 1.0 : -1.0;
//*DFEItr = *dPtr;
*dPtr = *dPtr * (*rotPtr);
DFEItr++;
rotPtr++;
revRotPtr++;
}
vectorSlicer(DFEoutput);
SoftVector *burstBits = new SoftVector(postForward->size());
SoftVector::iterator burstItr = burstBits->begin();
DFEItr = DFEoutput->begin();
for (; DFEItr < DFEoutput->end(); DFEItr++)
*burstItr++ = DFEItr->real();
delete postForward;
delete DFEoutput;
return burstBits;
}
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