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Transceiver52M: Setup dual Laurent pulse shaping filter 

Provides substantially improved transmit phase error
performance when enabled. Requires use of 4 samples
per symbol, and is enabled by default when set.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
This commit is contained in:
Thomas Tsou 2013-09-05 08:16:47 +08:00
parent 84c60f6679
commit a57bc8a3b9
3 changed files with 221 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
Transceiver52M/UHDDevice.cpp
View File

@ -62,18 +62,14 @@ struct uhd_dev_offset {
* Notes:
* USRP1 with timestamps is not supported by UHD.
*/
static struct uhd_dev_offset uhd_offsets[NUM_USRP_TYPES * 3] = {
static struct uhd_dev_offset uhd_offsets[NUM_USRP_TYPES * 2] = {
{ USRP1, 1, 0.0 },
{ USRP1, 2, 0.0 },
{ USRP1, 4, 0.0 },
{ USRP2, 1, 5.4394e-5 },
{ USRP2, 2, 0.0 },
{ USRP2, 4, 0.0 },
{ B100, 1, 9.4778e-5 },
{ B100, 2, 5.1100e-5 },
{ B100, 4, 2.9418e-5 },
{ UMTRX, 1, 9.4778e-5 },
{ UMTRX, 2, 0.0 },
{ UMTRX, 4, 0.0 },
};
@ -86,25 +82,23 @@ static double get_dev_offset(enum uhd_dev_type type, int sps)
switch (sps) {
case 1:
return uhd_offsets[3 * type + 0].offset;
case 2:
return uhd_offsets[3 * type + 1].offset;
return uhd_offsets[2 * type + 0].offset;
case 4:
return uhd_offsets[3 * type + 2].offset;
return uhd_offsets[2 * type + 1].offset;
}
LOG(ERR) << "Unsupported samples-per-symbols: " << sps;
return 0.0;
return 0.0;
}
/*
* Select sample rate based on device type and requested samples-per-symbol.
* The base rate is either GSM symbol rate, 270.833 kHz, or the minimum
* usable channel spacing of 400 kHz.
*/
*/
static double select_rate(uhd_dev_type type, int sps)
{
if ((sps != 4) && (sps != 2) && (sps != 1))
if ((sps != 4) && (sps != 1))
return -9999.99;
switch (type) {

2
Transceiver52M/radioInterface.h
View File

@ -22,7 +22,7 @@
#include "radioClock.h"
/** samples per GSM symbol */
#define SAMPSPERSYM 1
#define SAMPSPERSYM 4
#define INCHUNK (625)
#define OUTCHUNK (625)

261
Transceiver52M/sigProcLib.cpp
View File

@ -77,20 +77,25 @@ struct CorrelationSequence {
* for SSE instructions.
*/
struct PulseSequence {
PulseSequence() : gaussian(NULL), empty(NULL), buffer(NULL)
PulseSequence() : c0(NULL), c1(NULL), empty(NULL),
c0_buffer(NULL), c1_buffer(NULL)
{
}
~PulseSequence()
{
delete gaussian;
delete c0;
delete c1;
delete empty;
free(buffer);
free(c0_buffer);
free(c1_buffer);
}
signalVector *gaussian;
signalVector *c0;
signalVector *c1;
signalVector *empty;
void *buffer;
void *c0_buffer;
void *c1_buffer;
};
CorrelationSequence *gMidambles[] = {NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL};
@ -409,10 +414,48 @@ signalVector *convolve(const signalVector *x,
return y;
}
bool generateC1Pulse(int sps)
{
int len;
switch (sps) {
case 4:
len = 8;
break;
default:
return false;
}
GSMPulse->c1_buffer = convolve_h_alloc(len);
GSMPulse->c1 = new signalVector((complex *)
GSMPulse->c1_buffer, 0, len);
GSMPulse->c1->isRealOnly(true);
/* Enable alignment for SSE usage */
GSMPulse->c1->setAligned(true);
signalVector::iterator xP = GSMPulse->c1->begin();
switch (sps) {
case 4:
/* BT = 0.30 */
*xP++ = 0.0;
*xP++ = 8.16373112e-03;
*xP++ = 2.84385729e-02;
*xP++ = 5.64158904e-02;
*xP++ = 7.05463553e-02;
*xP++ = 5.64158904e-02;
*xP++ = 2.84385729e-02;
*xP++ = 8.16373112e-03;
}
return true;
}
void generateGSMPulse(int sps, int symbolLength)
{
int len;
float arg, center;
float arg, avg, center;
delete GSMPulse;
@ -438,15 +481,18 @@ void generateGSMPulse(int sps, int symbolLength)
len = 4;
}
GSMPulse->buffer = convolve_h_alloc(len);
GSMPulse->gaussian = new signalVector((complex *)
GSMPulse->buffer, 0, len);
GSMPulse->gaussian->setAligned(true);
GSMPulse->gaussian->isRealOnly(true);
GSMPulse->c0_buffer = convolve_h_alloc(len);
GSMPulse->c0 = new signalVector((complex *)
GSMPulse->c0_buffer, 0, len);
GSMPulse->c0->isRealOnly(true);
signalVector::iterator xP = GSMPulse->gaussian->begin();
/* Enable alingnment for SSE usage */
GSMPulse->c0->setAligned(true);
signalVector::iterator xP = GSMPulse->c0->begin();
if (sps == 4) {
*xP++ = 0.0;
*xP++ = 4.46348606e-03;
*xP++ = 2.84385729e-02;
*xP++ = 1.03184855e-01;
@ -462,7 +508,7 @@ void generateGSMPulse(int sps, int symbolLength)
*xP++ = 1.03184855e-01;
*xP++ = 2.84385729e-02;
*xP++ = 4.46348606e-03;
*xP++ = 0.0;
generateC1Pulse(sps);
} else {
center = (float) (len - 1.0) / 2.0;
@ -472,12 +518,12 @@ void generateGSMPulse(int sps, int symbolLength)
*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;
avg = sqrtf(vectorNorm2(*GSMPulse->c0) / sps);
xP = GSMPulse->c0->begin();
for (int i = 0; i < len; i++)
*xP++ /= avg;
}
}
signalVector* frequencyShift(signalVector *y,
@ -559,43 +605,160 @@ bool vectorSlicer(signalVector *x)
return true;
}
static signalVector *rotateBurst(const BitVector &wBurst,
int guardPeriodLength, int sps)
{
int burst_len;
signalVector *pulse, rotated, *shaped;
signalVector::iterator itr;
pulse = GSMPulse->empty;
burst_len = sps * (wBurst.size() + guardPeriodLength);
rotated = signalVector(burst_len);
itr = rotated.begin();
for (unsigned i = 0; i < wBurst.size(); i++) {
*itr = 2.0 * (wBurst[i] & 0x01) - 1.0;
itr += sps;
}
GMSKRotate(rotated);
rotated.isRealOnly(false);
/* Dummy filter operation */
shaped = convolve(&rotated, pulse, NULL, START_ONLY);
if (!shaped)
return NULL;
return shaped;
}
static signalVector *modulateBurstLaurent(const BitVector &bits,
int guard_len, int sps)
{
int burst_len;
float phase;
signalVector *c0_pulse, *c1_pulse, c0_burst, 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 = signalVector(burst_len);
c0_burst.isRealOnly(true);
c0_itr = c0_burst.begin();
c1_burst = signalVector(burst_len);
c1_burst.isRealOnly(true);
c1_itr = c1_burst.begin();
/* Padded differential start bits */
*c0_itr = 2.0 * (0x00 & 0x01) - 1.0;
c0_itr += sps;
/* Main burst bits */
for (unsigned i = 0; i < bits.size(); i++) {
*c0_itr = 2.0 * (bits[i] & 0x01) - 1.0;
c0_itr += sps;
}
/* Padded differential end bits */
*c0_itr = 2.0 * (0x01 & 0x01) - 1.0;
/* Generate C0 phase coefficients */
GMSKRotate(c0_burst);
c0_burst.isRealOnly(false);
c0_itr = c0_burst.begin();
c0_itr += sps * 2;
c1_itr += sps * 2;
/* Start magic */
phase = 2.0 * ((0x01 & 0x01) ^ (0x01 & 0x01)) - 1.0;
*c1_itr = *c0_itr * Complex<float>(0, phase);
c0_itr += sps;
c1_itr += sps;
/* Generate C1 phase coefficients */
for (unsigned i = 2; i < bits.size(); i++) {
phase = 2.0 * ((bits[i - 1] & 0x01) ^ (bits[i - 2] & 0x01)) - 1.0;
*c1_itr = *c0_itr * Complex<float>(0, phase);
c0_itr += sps;
c1_itr += sps;
}
/* End magic */
int i = bits.size();
phase = 2.0 * ((bits[i-1] & 0x01) ^ (bits[i-2] & 0x01)) - 1.0;
*c1_itr = *c0_itr * Complex<float>(0, phase);
/* Primary (C0) and secondary (C1) pulse shaping */
c0_shaped = convolve(&c0_burst, c0_pulse, NULL, START_ONLY);
c1_shaped = convolve(&c1_burst, c1_pulse, NULL, START_ONLY);
/* Sum shaped outputs into C0 */
c0_itr = c0_shaped->begin();
c1_itr = c1_shaped->begin();
for (unsigned i = 0; i < c0_shaped->size(); i++ )
*c0_itr++ += *c1_itr++;
delete c1_shaped;
return c0_shaped;
}
static signalVector *modulateBurstBasic(const BitVector &bits,
int guard_len, int sps)
{
int burst_len;
signalVector *pulse, burst, *shaped;
signalVector::iterator burst_itr;
pulse = GSMPulse->c0;
burst_len = sps * (bits.size() + guard_len);
burst = signalVector(burst_len);
burst.isRealOnly(true);
burst_itr = burst.begin();
/* Raw bits are not differentially encoded */
for (unsigned i = 0; i < bits.size(); i++) {
*burst_itr = 2.0 * (bits[i] & 0x01) - 1.0;
burst_itr += sps;
}
GMSKRotate(burst);
burst.isRealOnly(false);
/* Single Gaussian pulse approximation shaping */
shaped = convolve(&burst, pulse, NULL, START_ONLY);
return shaped;
}
/* 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;
return rotateBurst(wBurst, guardPeriodLength, sps);
else if (sps == 4)
return modulateBurstLaurent(wBurst, guardPeriodLength, sps);
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;
return modulateBurstBasic(wBurst, guardPeriodLength, sps);
}
float sinc(float x)
float sinc(float x)
{
if ((x >= 0.01F) || (x <= -0.01F)) return (sinLookup(x)/x);
return 1.0F;
@ -1040,6 +1203,10 @@ static int detectBurst(signalVector &burst,
/* Normalize our channel gain */
*amp = *amp / sync->gain;
/* Compenate for residual rotation with dual Laurent pulse */
if (sps == 4)
*amp = *amp * complex(0.0, 1.0);
return 1;
}