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C

/**
*
* \section COPYRIGHT
*
* Copyright 2013-2014 The libLTE Developers. See the
* COPYRIGHT file at the top-level directory of this distribution.
*
* \section LICENSE
*
* This file is part of the libLTE library.
*
* libLTE is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3 of
* the License, or (at your option) any later version.
*
* libLTE 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 Lesser General Public License for more details.
*
* A copy of the GNU Lesser General Public License can be found in
* the LICENSE file in the top-level directory of this distribution
* and at http://www.gnu.org/licenses/.
*
*/
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
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#include <strings.h>
#include <unistd.h>
#include <math.h>
#include <time.h>
#include "liblte/phy/phy.h"
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#include "viterbi_test.h"
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typedef _Complex float cf_t;
int frame_length = 1000, nof_frames = 128;
float ebno_db = 100.0;
uint32_t seed = 0;
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bool tail_biting = false;
int K = -1;
#define SNR_POINTS 10
#define SNR_MIN 0.0
#define SNR_MAX 5.0
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#define NCODS 3
#define NTYPES 1+NCODS
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void usage(char *prog) {
printf("Usage: %s [nlestk]\n", prog);
printf("\t-n nof_frames [Default %d]\n", nof_frames);
printf("\t-l frame_length [Default %d]\n", frame_length);
printf("\t-e ebno in dB [Default scan]\n");
printf("\t-s seed [Default 0=time]\n");
printf("\t-t tail_bitting [Default %s]\n", tail_biting ? "yes" : "no");
printf("\t-k constraint length [Default both]\n", K);
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}
void parse_args(int argc, char **argv) {
int opt;
while ((opt = getopt(argc, argv, "nlstek")) != -1) {
switch (opt) {
case 'n':
nof_frames = atoi(argv[optind]);
break;
case 'l':
frame_length = atoi(argv[optind]);
break;
case 'e':
ebno_db = atof(argv[optind]);
break;
case 's':
seed = (uint32_t) strtoul(argv[optind], NULL, 0);
break;
case 't':
tail_biting = true;
break;
case 'k':
K = atoi(argv[optind]);
break;
default:
usage(argv[0]);
exit(-1);
}
}
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}
void output_matlab(float ber[NTYPES][SNR_POINTS], int snr_points,
convcoder_t cod[NCODS], int ncods) {
int i, j, n;
FILE *f = fopen("viterbi_snr.m", "w");
if (!f) {
perror("fopen");
exit(-1);
}
fprintf(f, "ber=[");
for (j = 0; j < NTYPES; j++) {
for (i = 0; i < snr_points; i++) {
fprintf(f, "%g ", ber[j][i]);
}
fprintf(f, "; ");
}
fprintf(f, "];\n");
fprintf(f, "snr=linspace(%g,%g-%g/%d,%d);\n", SNR_MIN, SNR_MAX, SNR_MAX,
snr_points, snr_points);
fprintf(f, "semilogy(snr,ber,snr,0.5*erfc(sqrt(10.^(snr/10))));\n");
fprintf(f, "legend('uncoded',");
for (n=0;n<ncods;n++) {
fprintf(f,"'1/3 K=%d%s',",cod[n].K,cod[n].tail_biting?" tb":"");
}
fprintf(f,"'theory-uncoded');");
fprintf(f, "grid on;\n");
fclose(f);
}
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int main(int argc, char **argv) {
int frame_cnt;
float *llr;
uint8_t *llr_c;
uint8_t *data_tx, *data_rx[NTYPES], *symbols;
int i, j;
float var[SNR_POINTS], varunc[SNR_POINTS];
int snr_points;
float ber[NTYPES][SNR_POINTS];
uint32_t errors[NTYPES];
viterbi_type_t viterbi_type[NCODS];
viterbi_t dec[NCODS];
convcoder_t cod[NCODS];
int coded_length[NCODS];
int n, ncods, max_coded_length;
parse_args(argc, argv);
if (!seed) {
seed = time(NULL);
}
srand(seed);
switch (K) {
case 9:
cod[0].poly[0] = 0x1ed;
cod[0].poly[1] = 0x19b;
cod[0].poly[2] = 0x127;
cod[0].tail_biting = false;
cod[0].K = 9;
viterbi_type[0] = viterbi_39;
ncods=1;
break;
case 7:
cod[0].poly[0] = 0x6D;
cod[0].poly[1] = 0x4F;
cod[0].poly[2] = 0x57;
cod[0].K = 7;
cod[0].tail_biting = tail_biting;
viterbi_type[0] = viterbi_37;
ncods=1;
break;
default:
cod[0].poly[0] = 0x1ed;
cod[0].poly[1] = 0x19b;
cod[0].poly[2] = 0x127;
cod[0].tail_biting = false;
cod[0].K = 9;
viterbi_type[0] = viterbi_39;
cod[1].poly[0] = 0x6D;
cod[1].poly[1] = 0x4F;
cod[1].poly[2] = 0x57;
cod[1].tail_biting = false;
cod[1].K = 7;
viterbi_type[1] = viterbi_37;
cod[2].poly[0] = 0x6D;
cod[2].poly[1] = 0x4F;
cod[2].poly[2] = 0x57;
cod[2].tail_biting = true;
cod[2].K = 7;
viterbi_type[2] = viterbi_37;
ncods=3;
}
max_coded_length = 0;
for (i=0;i<ncods;i++) {
cod[i].R = 3;
coded_length[i] = cod[i].R * (frame_length + ((cod[i].tail_biting) ? 0 : cod[i].K - 1));
if (coded_length[i] > max_coded_length) {
max_coded_length = coded_length[i];
}
viterbi_init(&dec[i], viterbi_type[i], cod[i].poly, frame_length, cod[i].tail_biting);
printf("Convolutional Code 1/3 K=%d Tail bitting: %s\n", cod[i].K, cod[i].tail_biting ? "yes" : "no");
}
printf(" Frame length: %d\n", frame_length);
if (ebno_db < 100.0) {
printf(" EbNo: %.2f\n", ebno_db);
}
data_tx = malloc(frame_length * sizeof(uint8_t));
if (!data_tx) {
perror("malloc");
exit(-1);
}
for (i = 0; i < NTYPES; i++) {
data_rx[i] = malloc(frame_length * sizeof(uint8_t));
if (!data_rx[i]) {
perror("malloc");
exit(-1);
}
}
symbols = malloc(max_coded_length * sizeof(uint8_t));
if (!symbols) {
perror("malloc");
exit(-1);
}
llr = malloc(max_coded_length * sizeof(float));
if (!llr) {
perror("malloc");
exit(-1);
}
llr_c = malloc(2 * max_coded_length * sizeof(uint8_t));
if (!llr_c) {
perror("malloc");
exit(-1);
}
float ebno_inc, esno_db;
ebno_inc = (SNR_MAX - SNR_MIN) / SNR_POINTS;
if (ebno_db == 100.0) {
snr_points = SNR_POINTS;
for (i = 0; i < snr_points; i++) {
ebno_db = SNR_MIN + i * ebno_inc;
esno_db = ebno_db + 10 * log10((double) 1 / 3);
var[i] = sqrt(1 / (pow(10, esno_db / 10)));
varunc[i] = sqrt(1 / (pow(10, ebno_db / 10)));
}
} else {
esno_db = ebno_db + 10 * log10((double) 1 / 3);
var[0] = sqrt(1 / (pow(10, esno_db / 10)));
varunc[0] = sqrt(1 / (pow(10, ebno_db / 10)));
snr_points = 1;
}
float Gain = 32;
for (i = 0; i < snr_points; i++) {
frame_cnt = 0;
for (j = 0; j < NTYPES; j++) {
errors[j] = 0;
}
while (frame_cnt < nof_frames) {
/* generate data_tx */
for (j = 0; j < frame_length; j++) {
data_tx[j] = rand() % 2;
}
/* uncoded BER */
for (j = 0; j < frame_length; j++) {
llr[j] = data_tx[j] ? sqrt(2) : -sqrt(2);
}
ch_awgn_f(llr, llr, varunc[i], frame_length);
for (j = 0; j < frame_length; j++) {
data_rx[0][j] = llr[j] > 0 ? 1 : 0;
}
/* coded BER */
for (n=0;n<ncods;n++) {
convcoder_encode(&cod[n], data_tx, symbols, frame_length);
for (j = 0; j < coded_length[n]; j++) {
llr[j] = symbols[j] ? sqrt(2) : -sqrt(2);
}
ch_awgn_f(llr, llr, var[i], coded_length[n]);
vec_quant_fuc(llr, llr_c, Gain, 127.5, 255, coded_length[n]);
/* decoder 1 */
viterbi_decode_uc(&dec[n], llr_c, data_rx[1+n], frame_length);
}
/* check errors */
for (j = 0; j < 1+ncods; j++) {
errors[j] += bit_diff(data_tx, data_rx[j], frame_length);
}
frame_cnt++;
printf("Eb/No: %3.2f %10d/%d ",
SNR_MIN + i * ebno_inc,frame_cnt,nof_frames);
for (n=0;n<1+ncods;n++) {
printf("BER: %.2e ",(float) errors[n] / (frame_cnt * frame_length));
}
printf("\r");
}
printf("\n");
for (j = 0; j < 1+ncods; j++) {
ber[j][i] = (float) errors[j] / (frame_cnt * frame_length);
}
if (snr_points == 1) {
printf("BER uncoded: %g\t%u errors\n",
(float) errors[0] / (frame_cnt * frame_length), errors[0]);
for (n=0;n<ncods;n++) {
printf("BER K=%d: %g\t%u errors\n",cod[n].K,
(float) errors[1+n] / (frame_cnt * frame_length), errors[1+n]);
}
}
}
for (n=0;n<ncods;n++) {
viterbi_free(&dec[n]);
}
free(data_tx);
free(symbols);
free(llr);
free(llr_c);
for (i = 0; i < NTYPES; i++) {
free(data_rx[i]);
}
if (snr_points == 1) {
int expected_errors = get_expected_errors(nof_frames,
seed, frame_length, K, tail_biting, ebno_db);
if (expected_errors == -1) {
fprintf(stderr, "Test parameters not defined in test_results.h\n");
exit(-1);
} else {
printf("errors =%d, expected =%d\n", errors[1], expected_errors);
exit(errors[1] > expected_errors);
}
} else {
printf("\n");
output_matlab(ber, snr_points, cod, ncods);
printf("Done\n");
exit(0);
}
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}