mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-01 16:13:57 -04:00
9a8d9bd2fa
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6272 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
339 lines
10 KiB
C
339 lines
10 KiB
C
/*
|
|
sfrsd.c
|
|
|
|
A soft-decision decoder for the JT65 (63,12) Reed-Solomon code.
|
|
|
|
This decoding scheme is built around Phil Karn's Berlekamp-Massey
|
|
errors and erasures decoder. The approach is inspired by a number of
|
|
publications, including the stochastic Chase decoder described
|
|
in "Stochastic Chase Decoding of Reed-Solomon Codes", by Leroux et al.,
|
|
IEEE Communications Letters, Vol. 14, No. 9, September 2010 and
|
|
"Soft-Decision Decoding of Reed-Solomon Codes Using Successive Error-
|
|
and-Erasure Decoding," by Soo-Woong Lee and B. V. K. Vijaya Kumar.
|
|
|
|
Steve Franke K9AN, Urbana IL, September 2015
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <unistd.h>
|
|
#include <time.h>
|
|
#include <string.h>
|
|
#include "rs.h"
|
|
#include "init_random_seed.h"
|
|
|
|
static void *rs;
|
|
|
|
//***************************************************************************
|
|
void usage(void)
|
|
{
|
|
printf("Usage: sfrsd [options...] <path to kvasd.dat>\n");
|
|
printf(" input file should be in kvasd format\n");
|
|
printf("\n");
|
|
printf("Options:\n");
|
|
printf(" -n number of random erasure vectors to try\n");
|
|
printf(" -v verbose\n");
|
|
}
|
|
|
|
int main(int argc, char *argv[]){
|
|
|
|
extern char *optarg;
|
|
extern int optind;
|
|
|
|
int rxdat[63], rxprob[63], rxdat2[63], rxprob2[63];
|
|
int workdat[63], correct[63];
|
|
int era_pos[51];
|
|
int c, i, numera, nerr, nn=63, kk=12;
|
|
char *infile;
|
|
|
|
FILE *datfile, *logfile;
|
|
int nsec, maxe, nads;
|
|
float xlambda;
|
|
int mrsym[63],mrprob[63],mr2sym[63],mr2prob[63];
|
|
int nsec2,ncount,dat4[12],bestdat[12];
|
|
int ntrials=10000;
|
|
int verbose=0;
|
|
int nhard=0,nhard_min=32768,nsoft=0,nsoft_min=32768, ncandidates;
|
|
|
|
while ( (c = getopt(argc, argv, "n:qv")) !=-1 ) {
|
|
switch (c) {
|
|
case 'n':
|
|
ntrials=(int)strtof(optarg,NULL);
|
|
printf("ntrials set to %d\n",ntrials);
|
|
break;
|
|
case 'v':
|
|
verbose=1;
|
|
break;
|
|
case 'q': //accept (and ignore) -q option for WSJT10 compatibility
|
|
break;
|
|
case '?':
|
|
usage();
|
|
exit(1);
|
|
}
|
|
}
|
|
|
|
if( optind+1 > argc) {
|
|
// usage();
|
|
// exit(1);
|
|
infile="kvasd.dat";
|
|
} else {
|
|
infile=argv[optind];
|
|
}
|
|
|
|
logfile=fopen("/tmp/sfrsd.log","a");
|
|
if( !logfile ) {
|
|
printf("Unable to open sfrsd.log\n");
|
|
exit(1);
|
|
}
|
|
|
|
datfile=fopen(infile,"rb");
|
|
if( !datfile ) {
|
|
printf("Unable to open kvasd.dat\n");
|
|
exit(1);
|
|
} else {
|
|
fread(&nsec,sizeof(int),1,datfile);
|
|
fread(&xlambda,sizeof(float),1,datfile);
|
|
fread(&maxe,sizeof(int),1,datfile);
|
|
fread(&nads,sizeof(int),1,datfile);
|
|
fread(&mrsym,sizeof(int),63,datfile);
|
|
fread(&mrprob,sizeof(int),63,datfile);
|
|
fread(&mr2sym,sizeof(int),63,datfile);
|
|
fread(&mr2prob,sizeof(int),63,datfile);
|
|
fread(&nsec2,sizeof(int),1,datfile);
|
|
fread(&ncount,sizeof(int),1,datfile);
|
|
// printf("ncount %d\n",ncount);
|
|
fread(&dat4,sizeof(int),12,datfile);
|
|
fclose(datfile);
|
|
}
|
|
|
|
// initialize the ka9q reed solomon encoder/decoder
|
|
unsigned int symsize=6, gfpoly=0x43, fcr=3, prim=1, nroots=51;
|
|
rs=init_rs_int(symsize, gfpoly, fcr, prim, nroots, 0);
|
|
|
|
/* // debug
|
|
int revdat[12], parity[51], correct[63];
|
|
for (i=0; i<12; i++) {
|
|
revdat[i]=dat4[11-i];
|
|
printf("%d ",revdat[i]);
|
|
}
|
|
printf("\n");
|
|
encode_rs_int(rs,revdat,parity);
|
|
for (i=0; i<63; i++) {
|
|
if( i<12 ) {
|
|
correct[i]=revdat[i];
|
|
printf("%d ",parity[i]);
|
|
} else {
|
|
correct[i]=parity[i-12];
|
|
}
|
|
}
|
|
printf("\n");
|
|
*/
|
|
|
|
// reverse the received symbol vector for bm decoder
|
|
for (i=0; i<63; i++) {
|
|
rxdat[i]=mrsym[62-i];
|
|
rxprob[i]=mrprob[62-i];
|
|
rxdat2[i]=mr2sym[62-i];
|
|
rxprob2[i]=mr2prob[62-i];
|
|
}
|
|
|
|
// sort the mrsym probabilities to find the least reliable symbols
|
|
int k, pass, tmp, nsym=63;
|
|
int probs[63], indexes[63];
|
|
for (i=0; i<63; i++) {
|
|
indexes[i]=i;
|
|
probs[i]=rxprob[i]; // must un-comment sfrsd metrics in demod64a
|
|
|
|
}
|
|
for (pass = 1; pass <= nsym-1; pass++) {
|
|
for (k = 0; k < nsym - pass; k++) {
|
|
if( probs[k] < probs[k+1] ) {
|
|
tmp = probs[k];
|
|
probs[k] = probs[k+1];
|
|
probs[k+1] = tmp;
|
|
tmp = indexes[k];
|
|
indexes[k] = indexes[k+1];
|
|
indexes[k+1] = tmp;
|
|
}
|
|
}
|
|
}
|
|
|
|
// see if we can decode using BM HDD (and calculate the syndrome vector)
|
|
memset(era_pos,0,51*sizeof(int));
|
|
numera=0;
|
|
memcpy(workdat,rxdat,sizeof(rxdat));
|
|
nerr=decode_rs_int(rs,workdat,era_pos,numera,1);
|
|
if( nerr >= 0 ) {
|
|
fprintf(logfile," BM decode nerrors= %3d : ",nerr);
|
|
for(i=0; i<12; i++) printf("%2d ",workdat[11-i]);
|
|
fprintf(logfile,"\n");
|
|
fclose(logfile);
|
|
exit(0);
|
|
}
|
|
|
|
// generate random erasure-locator vectors and see if any of them
|
|
// decode. This will generate a list of potential codewords. The
|
|
// "soft" distance between each codeword and the received word is
|
|
// used to decide which codeword is "best".
|
|
//
|
|
|
|
init_random_seed();
|
|
|
|
float p_erase;
|
|
int thresh, nsum;
|
|
ncandidates=0;
|
|
|
|
|
|
for( k=0; k<ntrials; k++) {
|
|
memset(era_pos,0,51*sizeof(int));
|
|
memcpy(workdat,rxdat,sizeof(rxdat));
|
|
|
|
// mark a subset of the symbols as erasures
|
|
numera=0;
|
|
for (i=0; i<nn; i++) {
|
|
p_erase=0.0;
|
|
if( probs[62-i] >= 255 ) {
|
|
p_erase = 0.5;
|
|
} else if ( probs[62-i] >= 196 ) {
|
|
p_erase = 0.6;
|
|
} else if ( probs[62-i] >= 128 ) {
|
|
p_erase = 0.6;
|
|
} else if ( probs[62-i] >= 32 ) {
|
|
p_erase = 0.6;
|
|
} else {
|
|
p_erase = 0.8;
|
|
}
|
|
thresh = p_erase*100;
|
|
long int ir;
|
|
ir=rand();
|
|
if( ((ir % 100) < thresh ) && numera < 51 ) {
|
|
era_pos[numera]=indexes[62-i];
|
|
numera=numera+1;
|
|
}
|
|
}
|
|
|
|
nerr=decode_rs_int(rs,workdat,era_pos,numera,0);
|
|
|
|
if( nerr >= 0 ) {
|
|
ncandidates=ncandidates+1;
|
|
for(i=0; i<12; i++) dat4[i]=workdat[11-i];
|
|
// fprintf(logfile,"loop1 decode nerr= %3d : ",nerr);
|
|
// for(i=0; i<12; i++) fprintf(logfile, "%2d ",dat4[i]);
|
|
// fprintf(logfile,"\n");
|
|
nhard=0;
|
|
nsoft=0;
|
|
nsum=0;
|
|
for (i=0; i<63; i++) {
|
|
nsum=nsum+rxprob[i];
|
|
if( workdat[i] != rxdat[i] ) {
|
|
nhard=nhard+1;
|
|
nsoft=nsoft+rxprob[i];
|
|
}
|
|
}
|
|
if( nsum != 0 ) {
|
|
nsoft=63*nsoft/nsum;
|
|
if( (nsoft < nsoft_min) ) {
|
|
nsoft_min=nsoft;
|
|
nhard_min=nhard;
|
|
memcpy(bestdat,dat4,12*sizeof(int));
|
|
memcpy(correct,workdat,63*sizeof(int));
|
|
}
|
|
|
|
} else {
|
|
fprintf(logfile,"error - nsum %d nsoft %d nhard %d\n",nsum,nsoft,nhard);
|
|
}
|
|
// if( ncandidates >= 5000 ) {
|
|
if( ncandidates >= ntrials/2 ) {
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
fprintf(logfile,"%d candidates after stochastic loop\n",ncandidates);
|
|
|
|
// do Forney Generalized Minimum Distance pattern
|
|
for (k=0; k<25; k++) {
|
|
memset(era_pos,0,51*sizeof(int));
|
|
numera=2*k;
|
|
for (i=0; i<numera; i++) {
|
|
era_pos[i]=indexes[62-i];
|
|
}
|
|
|
|
memcpy(workdat,rxdat,sizeof(rxdat));
|
|
nerr=decode_rs_int(rs,workdat,era_pos,numera,0);
|
|
|
|
if( nerr >= 0 ) {
|
|
ncandidates=ncandidates+1;
|
|
for(i=0; i<12; i++) dat4[i]=workdat[11-i];
|
|
// fprintf(logfile,"GMD decode nerr= %3d : ",nerr);
|
|
// for(i=0; i<12; i++) fprintf(logfile, "%2d ",dat4[i]);
|
|
// fprintf(logfile,"\n");
|
|
nhard=0;
|
|
nsoft=0;
|
|
nsum=0;
|
|
for (i=0; i<63; i++) {
|
|
nsum=nsum+rxprob[i];
|
|
if( workdat[i] != rxdat[i] ) {
|
|
nhard=nhard+1;
|
|
nsoft=nsoft+rxprob[i];
|
|
}
|
|
}
|
|
if( nsum != 0 ) {
|
|
nsoft=63*nsoft/nsum;
|
|
if( (nsoft < nsoft_min) ) {
|
|
nsoft_min=nsoft;
|
|
nhard_min=nhard;
|
|
memcpy(bestdat,dat4,12*sizeof(int));
|
|
memcpy(correct,workdat,63*sizeof(int));
|
|
}
|
|
|
|
} else {
|
|
fprintf(logfile,"error - nsum %d nsoft %d nhard %d\n",nsum,nsoft,nhard);
|
|
}
|
|
// if( ncandidates >=5000 ) {
|
|
if( ncandidates >= ntrials/2 ) {
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
fprintf(logfile,"%d candidates after GMD\n",ncandidates);
|
|
|
|
if( (ncandidates >= 0) && (nsoft_min < 36) && (nhard_min < 44) ) {
|
|
for (i=0; i<63; i++) {
|
|
fprintf(logfile,"%3d %3d %3d %3d %3d %3d\n",i,correct[i],rxdat[i],rxprob[i],rxdat2[i],rxprob2[i]);
|
|
// fprintf(logfile,"%3d %3d %3d %3d %3d\n",i,workdat[i],rxdat[i],rxprob[i],rxdat2[i],rxprob2[i]);
|
|
}
|
|
|
|
fprintf(logfile,"**** ncandidates %d nhard %d nsoft %d nsum %d\n",ncandidates,nhard_min,nsoft_min,nsum);
|
|
} else {
|
|
nhard_min=-1;
|
|
memset(bestdat,0,12*sizeof(int));
|
|
}
|
|
datfile=fopen(infile,"wb");
|
|
if( !datfile ) {
|
|
printf("Unable to open kvasd.dat\n");
|
|
return 1;
|
|
} else {
|
|
fwrite(&nsec,sizeof(int),1,datfile);
|
|
fwrite(&xlambda,sizeof(float),1,datfile);
|
|
fwrite(&maxe,sizeof(int),1,datfile);
|
|
fwrite(&nads,sizeof(int),1,datfile);
|
|
fwrite(&mrsym,sizeof(int),63,datfile);
|
|
fwrite(&mrprob,sizeof(int),63,datfile);
|
|
fwrite(&mr2sym,sizeof(int),63,datfile);
|
|
fwrite(&mr2prob,sizeof(int),63,datfile);
|
|
fwrite(&nsec2,sizeof(int),1,datfile);
|
|
fwrite(&nhard_min,sizeof(int),1,datfile);
|
|
fwrite(&bestdat,sizeof(int),12,datfile);
|
|
fclose(datfile);
|
|
}
|
|
|
|
fprintf(logfile,"exiting sfrsd\n");
|
|
fflush(logfile);
|
|
fclose(logfile);
|
|
exit(0);
|
|
}
|
|
|
|
|