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/*
FILE...: ldpc_dec.c
AUTHOR.: Matthew C. Valenti, Rohit Iyer Seshadri, David Rowe
CREATED: Sep 2016
Command line C LDPC decoder derived from MpDecode.c in the CML
library. Allows us to run the same decoder in Octave and C.
*/
#include <assert.h>
#include <errno.h>
#include <math.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include "mpdecode_core.h"
#include "ldpc_codes.h"
#include "ofdm_internal.h"
int opt_exists(char *argv[], int argc, char opt[]) {
int i;
for (i=0; i<argc; i++) {
if (strcmp(argv[i], opt) == 0) {
return i;
}
}
return 0;
}
int main(int argc, char *argv[])
{
int CodeLength, NumberParityBits;
int i, codename, parityCheckCount, mute, testframes;
int data_bits_per_frame;
struct LDPC ldpc;
int iter, total_iters;
int Tbits, Terrs, Tbits_raw, Terrs_raw, Tpackets, Tpacketerrs;
int unused_data_bits = 84;
if (argc < 2) {
fprintf(stderr, "\n");
fprintf(stderr, "usage: %s --listcodes\n\n", argv[0]);
fprintf(stderr, " List supported codes (more can be added via using Octave ldpc scripts)\n");
fprintf(stderr, "\n");
fprintf(stderr, "usage: %s InOneSymbolPerFloat OutOneBitPerByte [--sd] [--half] [--code CodeName] [--testframes]", argv[0]);
fprintf(stderr, " [--unused numUnusedDataBits]\n\n");
fprintf(stderr, " InOneSymbolPerFloat Input file of float LLRs, use - for the \n");
fprintf(stderr, " file names to use stdin/stdout\n");
fprintf(stderr, " --code Use LDPC code CodeName\n");
fprintf(stderr, " --listcodes List available LDPC codes\n");
fprintf(stderr, " --sd Treat input file samples as BPSK Soft Decision\n");
fprintf(stderr, " demod outputs rather than LLRs\n");
fprintf(stderr, " --mute Only output frames with < 10%% parity check fails\n");
fprintf(stderr, " --testframes built in test frame modem, requires --testframes at encoder\n");
fprintf(stderr, " --unused number of unused data bits, which are set to 1's at enc and dec\n");
fprintf(stderr, "\n");
fprintf(stderr, "Example in testframe mode:\n\n");
fprintf(stderr, " $ ./ldpc_enc /dev/zero - --sd --code HRA_112_112 --testframes 10 |\n");
fprintf(stderr, " ./ldpc_dec - /dev/null --code HRA_112_112 --sd --testframes\n");
exit(0);
}
if ((codename = opt_exists(argv, argc, "--listcodes")) != 0) {
ldpc_codes_list();
exit(0);
}
/* set up LDPC code */
int code_index = 0;
if ((codename = opt_exists(argv, argc, "--code")) != 0)
code_index = ldpc_codes_find(argv[codename+1]);
memcpy(&ldpc,&ldpc_codes[code_index],sizeof(struct LDPC));
fprintf(stderr, "Using: %s\n", ldpc.name);
CodeLength = ldpc.CodeLength; /* length of entire codeword */
NumberParityBits = ldpc.NumberParityBits;
data_bits_per_frame = ldpc.NumberRowsHcols;
unsigned char ibits[data_bits_per_frame];
unsigned char pbits[NumberParityBits];
uint8_t out_char[CodeLength];
testframes = 0;
total_iters = 0;
Tbits = Terrs = Tbits_raw = Terrs_raw = Tpackets = Tpacketerrs = 0;
FILE *fin, *fout;
int sdinput, nread, offset=0;
/* File I/O mode ------------------------------------------------*/
if (strcmp(argv[1], "-") == 0) fin = stdin;
else if ( (fin = fopen(argv[1],"rb")) == NULL ) {
fprintf(stderr, "Error opening input SD file: %s: %s.\n",
argv[1], strerror(errno));
exit(1);
}
if (strcmp(argv[2], "-") == 0) fout = stdout;
else if ( (fout = fopen(argv[2],"wb")) == NULL ) {
fprintf(stderr, "Error opening output bit file: %s: %s.\n",
argv[2], strerror(errno));
exit(1);
}
sdinput = 0; mute = 0; testframes = 0;
if (opt_exists(argv, argc, "--sd")) {
sdinput = 1;
}
if (opt_exists(argv, argc, "--mute")) {
mute = 1;
}
unused_data_bits = 0; int arg;
if ((arg = opt_exists(argv, argc, "--unused"))) {
unused_data_bits = atoi(argv[arg+1]);
}
if (opt_exists(argv, argc, "--testframes")) {
testframes = 1;
uint16_t r[data_bits_per_frame];
ofdm_rand(r, data_bits_per_frame);
for(i=0; i<data_bits_per_frame-unused_data_bits; i++) {
ibits[i] = r[i] > 16384;
}
for(i=data_bits_per_frame-unused_data_bits; i<data_bits_per_frame; i++) {
ibits[i] = 1;
}
encode(&ldpc, ibits, pbits);
}
float *input_float = calloc(CodeLength, sizeof(float));
nread = CodeLength - unused_data_bits;
fprintf(stderr, "CodeLength: %d offset: %d\n", CodeLength, offset);
while(fread(input_float, sizeof(float), nread, fin) == nread) {
if (testframes) {
/* BPSK SD and bit LLRs get mapped roughly the same way so this just happens to work for both */
char in_char;
for (i=0; i<data_bits_per_frame-unused_data_bits; i++) {
in_char = input_float[i] < 0;
if (in_char != ibits[i]) {
Terrs_raw++;
}
Tbits_raw++;
}
for (i=0; i<NumberParityBits; i++) {
in_char = input_float[i+data_bits_per_frame-unused_data_bits] < 0;
if (in_char != pbits[i]) {
Terrs_raw++;
}
Tbits_raw++;
}
}
if (sdinput) {
/* map BPSK SDs to bit LLRs */
float llr[CodeLength-unused_data_bits];
sd_to_llr(llr, input_float, CodeLength-unused_data_bits);
/* insert unused data LLRs */
float llr_tmp[CodeLength];
for(i=0; i<data_bits_per_frame-unused_data_bits; i++)
llr_tmp[i] = llr[i]; // rx data bits
for(i=data_bits_per_frame-unused_data_bits; i<data_bits_per_frame; i++)
llr_tmp[i] = -10.0; // known data bits high likelhood
for(i=data_bits_per_frame; i<CodeLength; i++)
llr_tmp[i] = llr[i-unused_data_bits]; // rx parity bits
memcpy(input_float, llr_tmp, sizeof(float)*CodeLength);
}
iter = run_ldpc_decoder(&ldpc, out_char, input_float, &parityCheckCount);
//fprintf(stderr, "iter: %d\n", iter);
total_iters += iter;
if (mute) {
// Output data bits only if decoder converged, or was
// within 10% of all parity checks converging (10% est
// BER). Useful for real world operation as it can
// resync and won't send crappy packets to the decoder
float ber_est = (float)(ldpc.NumberParityBits - parityCheckCount)/ldpc.NumberParityBits;
//fprintf(stderr, "iter: %4d parityCheckErrors: %4d ber: %3.2f\n", iter, ldpc.NumberParityBits - parityCheckCount, ber_est);
if (ber_est < 0.1) {
fwrite(out_char, sizeof(char), ldpc.NumberRowsHcols, fout);
}
}
fwrite(out_char, sizeof(char), data_bits_per_frame, fout);
if (testframes) {
int perr = 0;
for (i=0; i<data_bits_per_frame; i++) {
if (out_char[i] != ibits[i]) {
Terrs++;
perr = 1;
}
Tbits++;
}
Tpackets++; if (perr) { Tpacketerrs++; fprintf(stderr,"x"); } else fprintf(stderr,".");
}
//fprintf(stderr, "Terrs_raw: %d Tbits_raw: %d Terr: %d Tbits: %d\n", Terrs_raw, Tbits_raw, Terrs, Tbits);
}
free(input_float);
if (fin != NULL) fclose(fin);
if (fout != NULL) fclose(fout);
fprintf(stderr, "total iters %d\n", total_iters);
if (testframes) {
fprintf(stderr, "Raw Tbits: %6d Terr: %6d BER: %4.3f\n", Tbits_raw, Terrs_raw,
(float)Terrs_raw/(Tbits_raw+1E-12));
float coded_ber = (float)Terrs/(Tbits+1E-12);
fprintf(stderr, "Coded Tbits: %6d Terr: %6d BER: %4.3f\n", Tbits, Terrs, coded_ber);
fprintf(stderr, " Tpkts: %6d Tper: %6d PER: %4.3f\n", Tpackets, Tpacketerrs, Tpacketerrs/(Tpackets+1E-12));
/* set return code for Ctest */
if (Tpackets && (coded_ber < 0.01))
return 0;
else
return 1;
}
return 0;
}
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