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Optimization of the LLR approx algorithm implementation

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master
marojevic 11 years ago
parent de1454cf7b
commit 76ba600c20
8 changed files with 616 additions and 15 deletions
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9
lte/phy/include/liblte/phy/modem/modem_table.h
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@ -40,12 +40,15 @@
typedef _Complex float cf_t;
typedef struct LIBLTE_API {
uint32_t idx[2][6][32];
uint32_t min_idx[2][64][6]; /* NEW: for each constellation point zone (2, 4, 16, 64 for BPSK, QPSK, 16QAM, 64QAM) the 2x(1, 2, 4, and 6 closest constellation points) for each bit, respectively. */
uint32_t d_idx[64][7]; /* NEW: for each constellation point zone (2, 4, 16, 64 for BPSK, QPSK, 16QAM, 64QAM) the 2, 3, 5 and 7 indices to constellation points that need to be computed for any recevied symbol modulated as BPSK, QPSK, 16QAM, and 64QAM, respectively. */
}soft_table_t;
typedef struct LIBLTE_API {
cf_t* symbol_table; // bit-to-symbol mapping
soft_table_t soft_table; // symbol-to-bit mapping (used in soft demodulating)
uint32_t nsymbols; // number of modulation symbols
cf_t* symbol_table; // bit-to-symbol mapping
soft_table_t soft_table; // symbol-to-bit mapping (used in soft demodulating)
uint32_t nsymbols; // number of modulation symbols
uint32_t nbits_x_symbol; // number of bits per symbol
}modem_table_t;

4
lte/phy/lib/modem/src/demod_soft.c
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@ -58,8 +58,10 @@ int demod_soft_demodulate(demod_soft_t *q, const cf_t* symbols, float* llr, int
q->table->symbol_table, q->table->soft_table.idx, q->sigma);
break;
case APPROX:
llr_approx(symbols, llr, nsymbols, q->table->nsymbols, q->table->nbits_x_symbol,
/* llr_approx(symbols, llr, nsymbols, q->table->nsymbols, q->table->nbits_x_symbol,
q->table->symbol_table, q->table->soft_table.idx, q->sigma);
*/ llr_approx(symbols, llr, nsymbols, q->table->nsymbols, q->table->nbits_x_symbol,
q->table->symbol_table, q->table->soft_table.idx, q->table->soft_table.d_idx, q->table->soft_table.min_idx, q->sigma);
break;
}
return nsymbols*q->table->nbits_x_symbol;

110
lte/phy/lib/modem/src/lte_tables.c
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@ -34,6 +34,8 @@
#include "liblte/phy/modem/modem_table.h"
#include "lte_tables.h"
void LLR_approx_params(const cf_t* table, soft_table_t *soft_table, int B);
/**
* Set the BPSK modulation table */
void set_BPSKtable(cf_t* table, soft_table_t *soft_table, bool compute_soft_demod)
@ -53,6 +55,18 @@ void set_BPSKtable(cf_t* table, soft_table_t *soft_table, bool compute_soft_demo
/* BSPK symbols containing a '0' and a '1' (only two symbols, 1 bit) */
soft_table->idx[0][0][0] = 0;
soft_table->idx[1][0][0] = 1;
/* set two matrices for LLR approx. calculation */
soft_table->min_idx[0][0][0] = 0;
soft_table->min_idx[0][1][0] = 0;
soft_table->min_idx[1][0][0] = 1;
soft_table->min_idx[1][1][0] = 1;
soft_table->d_idx[0][0] = 0;
soft_table->d_idx[0][1] = 1;
soft_table->d_idx[1][0] = 0;
soft_table->d_idx[1][1] = 1;
}
/**
@ -91,6 +105,8 @@ void set_QPSKtable(cf_t* table, soft_table_t *soft_table, bool compute_soft_demo
soft_table->idx[1][0][1] = 3;
soft_table->idx[1][1][0] = 1;
soft_table->idx[1][1][1] = 3;
LLR_approx_params(table, soft_table, 2); /* last param indicating B (bits per symbol) */
}
/**
@ -156,6 +172,8 @@ void set_16QAMtable(cf_t* table, soft_table_t *soft_table, bool compute_soft_dem
soft_table->idx[0][3][i] = 2*i;
soft_table->idx[1][3][i] = 2*i+1;
}
LLR_approx_params(table, soft_table, 4); /* last param indication B (bits per symbol) */
}
/**
@ -277,4 +295,96 @@ void set_64QAMtable(cf_t* table, soft_table_t *soft_table, bool compute_soft_dem
soft_table->idx[0][5][i] = 2*i;
soft_table->idx[1][5][i] = 2*i+1;
}
LLR_approx_params(table, soft_table, 6); /* last param indication modulation */
}
/* Precompute two tables for calculating the distances based on the received symbol location relative to the constellation points */
void LLR_approx_params(const cf_t* table, soft_table_t *soft_table, int B) {
int i, j, b, k;
float x, y, d0, d1, min_d0, min_d1;
int M, D;
uint32_t min_idx0[64][6], min_idx1[64][6];
uint32_t count;
int flag;
D = B+1; /* number of different distances to be computed */
//M = pow(2,B); /* number of constellation points */
switch (B) {
case 1: {M = 2; break;} /* BPSK */
case 2: {M = 4; break;} /* QPSK */
case 4: {M = 16; break;} /* 16QAM */
case 6: {M = 64; break;} /* 64QAM */
default: {M = 4; break;} /* QPSK */
}
for (i=0;i<M;i++) { /* constellation points */
for (b=0;b<B;b++) { /* bits per symbol */
min_d0 = 100;
min_d1 = 100;
for (j=0;j<M/2;j++) { /* half the symbols have a '0', the other half a '1' at any bit position of modulation symbol */
x = __real__ table[i] - __real__ table[soft_table->idx[0][b][j]];
y = __imag__ table[i] - __imag__ table[soft_table->idx[0][b][j]];
d0 = x*x + y*y;
if (d0 < min_d0) {
min_d0 = d0;
min_idx0[i][b] = soft_table->idx[0][b][j];
}
x = __real__ table[i] - __real__ table[soft_table->idx[1][b][j]];
y = __imag__ table[i] - __imag__ table[soft_table->idx[1][b][j]];
d1 = x*x + y*y;
if (d1 < min_d1) {
min_d1 = d1;
min_idx1[i][b] = soft_table->idx[1][b][j];
}
}
}
}
for (i=0;i<M;i++) {
for (j=0;j<D;j++) {
soft_table->d_idx[i][j] = -1; /* intialization */
}
}
for (i=0;i<M;i++) {
count = 0;
for (b=0;b<B;b++) { /* bit(b) = 0 */
flag = 0;
for (k=0;k<count;k++) {
if (min_idx0[i][b] == soft_table->d_idx[i][k]) {
soft_table->min_idx[0][i][b] = k;
flag = 1; /* no new entry to idxdx */
break;
}
}
if (flag == 0) { /* new entry to min and d_idx */
soft_table->d_idx[i][count] = min_idx0[i][b];
soft_table->min_idx[0][i][b] = count;
count++;
}
}
for (b=0;b<B;b++) { /* bit(b) = 1 */
flag = 0;
for (k=0;k<count;k++) {
if (min_idx1[i][b] == soft_table->d_idx[i][k]) {
soft_table->min_idx[1][i][b] = k;
flag = 1; /* no new entry to d_idx */
break;
}
}
if (flag == 0) { /* new entry to min and d_idx */
soft_table->d_idx[i][count] = min_idx1[i][b];
soft_table->min_idx[1][i][b] = count;
count++;
}
}
}
}

8
lte/phy/lib/modem/src/lte_tables.h
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@ -38,6 +38,14 @@
#define QAM64_LEVEL_3 5/sqrt(42)
#define QAM64_LEVEL_4 7/sqrt(42)
//////////////// NUEVO //////////////////////
/* HARD DEMODULATION Thresholds, necessary for obtaining the zone of received symbol for optimized LLR approx implementation */
#define QAM16_THRESHOLD 2/sqrt(10)
#define QAM64_THRESHOLD_1 2/sqrt(42)
#define QAM64_THRESHOLD_2 4/sqrt(42)
#define QAM64_THRESHOLD_3 6/sqrt(42)
//=========================================//
#define QAM64_LEVEL_x 2/sqrt(42)
/* this is not an QAM64 level, but, rather, an auxiliary value that can be used for computing the
* symbol from the bit sequence */

473
lte/phy/lib/modem/src/soft_algs.c
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@ -31,16 +31,468 @@
#include <math.h>
#include <complex.h>
#include <stdint.h>
#include <string.h>
#include "soft_algs.h"
#include "liblte/phy/utils/vector.h"
#define LLR_APPROX_USE_VOLK
#define QAM16_THRESHOLD 2/sqrt(10)
#define QAM64_THRESHOLD_1 2/sqrt(42)
#define QAM64_THRESHOLD_2 4/sqrt(42)
#define QAM64_THRESHOLD_3 6/sqrt(42)
#ifdef LLR_APPROX_USE_VOLK
typedef _Complex float cf_t;
//#define LLR_APPROX_USE_VOLK
#define LLR_APPROX_OPT
#ifdef LLR_APPROX_OPT
float dd[10000][7]; ////// NUEVO: 7 distances that are needed to compute LLR approx for 64QAM
uint32_t zone[10000]; ////// NUEVO: zone of received symbol with respect to grid of QAM constellation diagram
/**
* @ingroup Received modulation symbol zone
* Determine location of received modulation symbol
*
* \param in input symbol (_Complex float)
* \param z associated zone in constellation diagram (int)
* \param N number of symbols
*/
static void zone_QPSK(const cf_t *in, uint32_t *z, int N) {
int s;
float re, im;
for (s=0;s<N;s++) {
re = __real__ in[s];
im = __imag__ in[s];
if (re > 0) {
if (im > 0) { /* 1st Quadrand (upper-right) */
z[s] = 0;
} else { /* 4th Quadrand (lower-right) */
z[s] = 1;
}
} else {
if (im > 0) { /* 2nd Quadrand (upper-left) */
z[s] = 2;
} else { /* 3rd Quadrand (lower-left) */
z[s] = 3;
}
}
}
}
/**
* @ingroup Received modulation symbol zone
* Determine location of received modulation symbol
*
* \param in input symbol (_Complex float)
* \param z associated zone in constellation diagram (int)
* \param N number of symbols
*/
static void zone_QAM16(const cf_t *in, uint32_t *z, int N) {
int s;
float re, im;
for (s=0;s<N;s++) {
re = __real__ in[s];
im = __imag__ in[s];
if (re > 0) {
if (im > 0) { /* 1st Quadrand (upper-right) */
if (re > QAM16_THRESHOLD) {
if (im > QAM16_THRESHOLD) {
z[s] = 3;
} else {
z[s] = 2;
}
} else {
if (im > QAM16_THRESHOLD) {
z[s] = 1;
} else {
z[s] = 0;
}
}
} else { /* 4th Quadrand (lower-right) */
if (re > QAM16_THRESHOLD) {
if (im < -QAM16_THRESHOLD) {
z[s] = 7;
} else {
z[s] = 6;
}
} else {
if (im < -QAM16_THRESHOLD) {
z[s] = 5;
} else {
z[s] = 4;
}
}
}
} else {
if (im > 0) { /* 2nd Quadrand (upper-left) */
if (re < -QAM16_THRESHOLD) {
if (im > QAM16_THRESHOLD) {
z[s] = 11;
} else {
z[s] = 10;
}
} else {
if (im > QAM16_THRESHOLD) {
z[s] = 9;
} else {
z[s] = 8;
}
}
} else { /* 3rd Quadrand (lower-left) */
if (re < -QAM16_THRESHOLD) {
if (im < -QAM16_THRESHOLD) {
z[s] = 15;
} else {
z[s] = 14;
}
} else {
if (im < -QAM16_THRESHOLD) {
z[s] = 13;
} else {
z[s] = 12;
}
}
}
}
}
}
/**
* @ingroup Received modulation symbol zone
* Determine location of received modulation symbol
*
* \param in input symbol (_Complex float)
* \param z associated zone in constellation diagram (int)
* \param N number of symbols
*/
static void zone_QAM64(const cf_t *in, uint32_t *z, int N) {
int s;
float re, im;
for (s=0;s<N;s++) {
re = __real__ in[s];
im = __imag__ in[s];
if (re > 0) {
if (im > 0) {
if (re > QAM64_THRESHOLD_2) {
if (re > QAM64_THRESHOLD_3) {
if (im > QAM64_THRESHOLD_2) {
if (im > QAM64_THRESHOLD_3) {
z[s] = 15;
} else {
z[s] = 14;
}
} else if (im > QAM64_THRESHOLD_1) {
z[s] = 10;
} else {
z[s] = 11;
}
} else {
if (im > QAM64_THRESHOLD_2) {
if (im > QAM64_THRESHOLD_3) {
z[s] = 13;
} else {
z[s] = 12;
}
} else if (im > QAM64_THRESHOLD_1) {
z[s] = 8;
} else {
z[s] = 9;
}
}
} else if (re > QAM64_THRESHOLD_1) {
if (im > QAM64_THRESHOLD_2) {
if (im > QAM64_THRESHOLD_3) {
z[s] = 5;
} else {
z[s] = 4;
}
} else if (im > QAM64_THRESHOLD_1) {
z[s] = 0;
} else {
z[s] = 1;
}
} else {
if (im > QAM64_THRESHOLD_2) {
if (im > QAM64_THRESHOLD_3) {
z[s] = 7;
} else {
z[s] = 6;
}
} else if (im > QAM64_THRESHOLD_1) {
z[s] = 2;
} else {
z[s] = 3;
}
}
} else { /* forth quadrant (lower-right) */
if (re > QAM64_THRESHOLD_2) {
if (re > QAM64_THRESHOLD_3) {
if (im < -QAM64_THRESHOLD_2) {
if (im < -QAM64_THRESHOLD_3) {
z[s] = 31;
} else {
z[s] = 30;
}
} else if (im < -QAM64_THRESHOLD_1) {
z[s] = 26;
} else {
z[s] = 27;
}
} else {
if (im < -QAM64_THRESHOLD_2) {
if (im < -QAM64_THRESHOLD_3) {
z[s] = 29;
} else {
z[s] = 28;
}
} else if (im < -QAM64_THRESHOLD_1) {
z[s] = 24;
} else {
z[s] = 25;
}
}
} else if (re > QAM64_THRESHOLD_1) {
if (im < -QAM64_THRESHOLD_2) {
if (im < -QAM64_THRESHOLD_3) {
z[s] = 21;
} else {
z[s] = 20;
}
} else if (im < -QAM64_THRESHOLD_1) {
z[s] = 16;
} else {
z[s] = 17;
}
} else {
if (im < -QAM64_THRESHOLD_2) {
if (im < -QAM64_THRESHOLD_3) {
z[s] = 23;
} else {
z[s] = 22;
}
} else if (im < -QAM64_THRESHOLD_1) {
z[s] = 18;
} else {
z[s] = 19;
}
}
}
} else { /* re < 0 */
if (im > 0) { /* second quadrant (upper-left) */
if (re < -QAM64_THRESHOLD_2) {
if (re < -QAM64_THRESHOLD_3) {
if (im > QAM64_THRESHOLD_2) {
if (im > QAM64_THRESHOLD_3) {
z[s] = 47;
} else {
z[s] = 46;
}
} else if (im > QAM64_THRESHOLD_1) {
z[s] = 42;
} else {
z[s] = 43;
}
} else {
if (im > QAM64_THRESHOLD_2) {
if (im > QAM64_THRESHOLD_3) {
z[s] = 45;
} else {
z[s] = 44;
}
} else if (im > QAM64_THRESHOLD_1) {
z[s] = 40;
} else {
z[s] = 41;
}
}
} else if (re < -QAM64_THRESHOLD_1) {
if (im > QAM64_THRESHOLD_2) {
if (im > QAM64_THRESHOLD_3) {
z[s] = 37;
} else {
z[s] = 36;
}
} else if (im > QAM64_THRESHOLD_1) {
z[s] = 32;
} else {
z[s] = 33;
}
} else {
if (im > QAM64_THRESHOLD_2) {
if (im > QAM64_THRESHOLD_3) {
z[s] = 39;
} else {
z[s] = 38;
}
} else if (im > QAM64_THRESHOLD_1) {
z[s] = 34;
} else {
z[s] = 35;
}
}
} else { /* third quadrant (lower-left) */
if (re < -QAM64_THRESHOLD_2) {
if (re < -QAM64_THRESHOLD_3) {
if (im < -QAM64_THRESHOLD_2) {
if (im < -QAM64_THRESHOLD_3) {
z[s] = 63;
} else {
z[s] = 62;
}
} else if (im < -QAM64_THRESHOLD_1) {
z[s] = 58;
} else {
z[s] = 59;
}
} else {
if (im < -QAM64_THRESHOLD_2) {
if (im < -QAM64_THRESHOLD_3) {
z[s] = 61;
} else {
z[s] = 60;
}
} else if (im < -QAM64_THRESHOLD_1) {
z[s] = 56;
} else {
z[s] = 57;
}
}
} else if (re < -QAM64_THRESHOLD_1) {
if (im < -QAM64_THRESHOLD_2) {
if (im < -QAM64_THRESHOLD_3) {
z[s] = 53;
} else {
z[s] = 52;
}
} else if (im < -QAM64_THRESHOLD_1) {
z[s] = 48;
} else {
z[s] = 49;
}
} else {
if (im < -QAM64_THRESHOLD_2) {
if (im < -QAM64_THRESHOLD_3) {
z[s] = 55;
} else {
z[s] = 54;
}
} else if (im < -QAM64_THRESHOLD_1) {
z[s] = 50;
} else {
z[s] = 51;
}
}
}
}
}
}
static void compute_zone(const cf_t *in, uint32_t *z, int N, int B)
{
switch(B) {
case 1: {memset(zone, 0, N*sizeof(int)); break;}/* BPSK */
case 2: {zone_QPSK(in, z, N); break;} /* QPSK */
case 4: {zone_QAM16(in, z, N); break;} /* 16QAM */
case 6: {zone_QAM64(in, z, N); break;} /* 64QAM */
}
}
static void compute_square_dist(const cf_t *in, cf_t *symbols, uint32_t (*idx)[7], int N, int B) {
int s, b;
float *d_ptr;
float x, y;
cf_t symbols_extract[7];
for (s=0;s<N;s++) { /* N: number of received symbols */
d_ptr = dd[s];
for (b=0;b<B+1;b++) {
symbols_extract[b] = symbols[idx[zone[s]][b]]; /* only subset of distances to constellation points needed for LLR approx */
//x = __real__ in[s] - __real__ symbols[idx[zone[s]][b]];
//y = __imag__ in[s] - __imag__ symbols[idx[zone[s]][b]];
//dd[s][b] = x*x + y*y;
//printf("\n%f + j %f", __real__ symbols_extract[b], __imag__ symbols_extract[b]);
}
vec_square_dist(in[s], symbols_extract, d_ptr, B+1);/* B+1 distances to be computed */
}
}
static void compute_llr(int N, int B, uint32_t (*min)[64][6], float sigma2, float *out) {
int s, b;
for (s = 0; s < N; s++) {
for (b = 0; b < B; b++) { /* bits per symbol */
out[s * B + b] = (dd[s][min[0][zone[s]][b]] - dd[s][min[1][zone[s]][b]]) / sigma2;
}
}
}
void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
_Complex float *symbols, uint32_t(*S)[6][32], uint32_t (*idx)[7], uint32_t (*min)[64][6], float sigma2)
{
if ((M == 2) || (M == 4) || (M == 16) || (M == 64)) {
compute_zone(in, zone, N, B);
compute_square_dist(in, symbols, idx, N, B);
compute_llr(N, B, min, sigma2, out);
}
}
#endif
#ifdef LLR_APPROX_USE_VOLK
float d[10000][64];
float num[10000], den[10000];
@ -76,14 +528,14 @@ static void compute_min_dist(uint32_t (*S)[6][32], int N, int B, int M) {
static void compute_llr(int N, int B, float sigma2, float *out) {
int s, b;
for (s = 0; s < N; s++) {
for (b = 0; b < B; b++) { /* bits per symbol */
for (b = 0; b < B; b++) { /* bits per symbol */
out[s * B + b] = (num[s * B + b]-den[s * B + b]) / sigma2;
}
}
}
void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
_Complex float *symbols, uint32_t(*S)[6][32], float sigma2)
_Complex float *symbols, uint32_t(*S)[6][32], uint32_t (*idx)[7], uint32_t (*min)[64][6], float sigma2)
{
if (M <= 64) {
@ -95,7 +547,9 @@ void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
}
}
#else
#endif
#ifdef LLR_APPROX_OLD
/**
* @ingroup Soft Modulation Demapping based on the approximate
@ -113,9 +567,8 @@ void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
* \param S Soft demapping auxiliary matrix
* \param sigma2 Noise vatiance
*/
void
llr_approx(const _Complex float *in, float *out, int N, int M, int B,
_Complex float *symbols, uint32_t(*S)[6][32], float sigma2)
void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
_Complex float *symbols, uint32_t(*S)[6][32], uint32_t (*idx)[7], uint32_t (*min)[64][6], float sigma2)
{
int i, s, b;
float num, den;
@ -150,9 +603,9 @@ llr_approx(const _Complex float *in, float *out, int N, int M, int B,
* with '1' are closer.
* Change sign if mapping negative to '0' and positive to '1' */
out[s * B + b] = change_sign * (den - num) / sigma2;
if (s<10)
/* if (s<10)
printf("out[%d]=%f=%f/%f\n",s*B+b,out[s*B+b], num,den);
}
*/ }
}
}

14
lte/phy/lib/modem/src/soft_algs.h
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@ -26,7 +26,7 @@
*/
void llr_approx(const _Complex float *in,
/*void llr_approx(const _Complex float *in,
float *out,
int N,
int M,
@ -34,6 +34,17 @@ void llr_approx(const _Complex float *in,
_Complex float *symbols,
uint32_t (*S)[6][32],
float sigma2);
*/
void llr_approx(const _Complex float *in,
float *out,
int N,
int M,
int B,
_Complex float *symbols,
uint32_t (*S)[6][32],
uint32_t (*idx)[7], /*64x7 table of integers [0..63], indices to 7 distances to be computed */
uint32_t (*min)[64][6], /*2x64x6 table of integers [0..6], indices to 2x6 nearest symbols */
float sigma2);
void llr_exact(const _Complex float *in,
float *out,
@ -43,3 +54,4 @@ void llr_exact(const _Complex float *in,
_Complex float *symbols,
uint32_t (*S)[6][32],
float sigma2);

12
lte/phy/lib/modem/test/modem_test.c
Unescape Escape View File

@ -36,6 +36,9 @@
#include "liblte/phy/phy.h"
time_t start, finish;
struct timeval x, y;
int num_bits = 1000;
lte_mod_t modulation;
bool soft_output = false, soft_exact = false;
@ -98,6 +101,10 @@ int main(int argc, char **argv) {
cf_t *symbols;
float *llr;
// unsigned long strt, fin;
// strt = x->tv_usec;
// fin = y->tv_usec;
parse_args(argc, argv);
/* initialize objects */
@ -156,7 +163,12 @@ int main(int argc, char **argv) {
/* demodulate */
if (soft_output) {
gettimeofday(&x, NULL);
demod_soft_demodulate(&demod_soft, symbols, llr, num_bits / mod.nbits_x_symbol);
gettimeofday(&y, NULL);
printf("\nElapsed time [ns]: %u\n", y.tv_usec - x.tv_usec);
for (i=0;i<num_bits;i++) {
output[i] = llr[i]>=0 ? 1 : 0;
}

1
lte/phy/lib/modem/test/soft_demod_test.c
Unescape Escape View File

@ -129,6 +129,7 @@ int main(int argc, char **argv) {
demod_soft_table_set(&demod_soft, &mod);
demod_soft_sigma_set(&demod_soft, 2.0 / mod.nbits_x_symbol);
/* allocate buffers */
input = malloc(sizeof(char) * num_bits);
if (!input) {

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