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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include <math.h>
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#include <assert.h>
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#include <getopt.h>
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#include "viterbi224.h"
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#include "fano.h"
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#include "sim.h"
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static inline int popcount(int x){
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return __builtin_popcount(x);
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}
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struct option Options[] = {
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{"scale",1, NULL, 'S'},
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{"delta",1, NULL, 'd'},
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{"max-cycles", 1, NULL, 'm'},
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{"frame-length",1,NULL,'l'},
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{"frame-count",1,NULL,'n'},
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{"ebn0",1,NULL,'e'},
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{"gain",1,NULL,'g'},
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{"verbose",0,NULL,'v'},
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{NULL},
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};
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int Nbits = 1024; // Bits per frame, INCLUDING TAIL that must be 0's
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double Signal = 30; // Signal amplitude (scaled to 8 bit byte)
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int Scale = 8; // Fano metric scaling factor
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const double Rate = 0.5; // Code rate = 1/2
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double Ebn0 = 2.0; // Digital signal-to-noise ratio per bit in dB
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unsigned long Maxcycles = 1000; // Maximum number of decoder moves per bit
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int Trials = 1000; // Number of frames to test
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int Verbose; // diag diarrhea
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int Zerodata; // Use all 0's data (no effect on linear codes)
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int main(int argc,char *argv[]){
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int mettab[2][256];
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unsigned char data[Nbits/8],symbols[Nbits*2],decode_data[Nbits/8];
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unsigned char xordata[Nbits/8];
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unsigned long cycles, metric;
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int delta = 4;
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time_t t;
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int trial,i,r;
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int errcnt;
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int fano_good_frames = 0;
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int fano_failures = 0;
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int fano_frame_errors = 0;
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int fano_bit_errors = 0;
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int viterbi_attempts = 0;
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int viterbi_good_frames = 0;
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int viterbi_frame_errors = 0;
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int viterbi_bit_errors = 0;
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long totcycles = 0;
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long histogram[256];
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double noise_amp; // Actual noise amplitude, computed from Signal amplitude & Eb/N0
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void *vp;
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while((i = getopt_long(argc,argv,"d:S:l:n:e:s:m:vz",Options,NULL)) != EOF){
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switch(i){
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case 'd':
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delta = atoi(optarg);
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break;
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case 'S':
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Scale = atoi(optarg);
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break;
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case 'm':
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Maxcycles = atoi(optarg);
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break;
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case 'l':
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Nbits = atoi(optarg);
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break;
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case 'n':
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Trials = atoi(optarg);
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break;
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case 'e':
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Ebn0 = atof(optarg);
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break;
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case 's':
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Signal = atof(optarg);
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break;
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case 'v':
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Verbose++;
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break;
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case 'z':
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Zerodata++;
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break;
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default:
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printf("Usage: %s [-m maxcycles/bit] [-l bits/frame] [-n numframes] [-e Eb/No] [-s signal_amplitude] [-v] [-z]\n",
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argv[0]);
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exit(1);
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break;
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}
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}
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if(Nbits < 64){
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printf("bits/frame must be >= 64\n");
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exit(1);
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}
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delta *= Scale;
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// Compute noise voltage. The factor of 2 accounts for BPSK seeing
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// only half the noise power, and the sqrt() converts power to voltage
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noise_amp = Signal / sqrt(2*Rate*pow(10.,Ebn0/10.));
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gen_met(mettab,Signal,noise_amp,Rate,Scale);
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// Generate channel transition matrix
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setup_channel(Signal,noise_amp);
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printf("Code rate %.2f, Nbits = %d, Maxcycles/bit %ld\n",Rate,Nbits,Maxcycles);
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printf("Eb/N0 = %.3lf dB, Signal = %lg, Noise = %lg, BER@Eb/N0 = %lg, BER@Es/N0 = %lg\n",
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Ebn0,Signal,noise_amp,0.5*erfc(pow(10.,Ebn0/20.)),0.5*erfc(sqrt(Rate*pow(10.,Ebn0/10.))));
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srandom(time(&t));
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memset(histogram,0,sizeof(histogram));
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memset(data,0,sizeof(data));
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for(trial = 0; trial < Trials; trial++){
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if(!Zerodata){
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// Generate random data
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// Note last 3 bytes must be 0 to tail off the encoder
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for(i=0;i<(Nbits-64)/8;i++) // allow room on end for max length tail
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data[i] = random() & 0xff;
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for(;i<Nbits/8;i++)
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data[i] = 0;
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}
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i = encode(symbols,data,sizeof(data));
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assert(i == 0);
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// Add noise & scale, build histogram
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for(i=0;i<2*Nbits;i++){
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symbols[i] = simulate(symbols[i]);
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histogram[symbols[i]]++;
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}
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if(Verbose > 2){
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printf("Cumulative symbol histogram:\n");
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for(i=0;i<256;i++){
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printf(" %6ld",histogram[i]);
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if((i % 16) == 15)
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putchar('\n');
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}
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}
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memset(decode_data,0,sizeof(decode_data));
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r = fano(&metric,&cycles,decode_data,symbols,Nbits,mettab,delta,Maxcycles);
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totcycles += cycles;
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if(r != 0){
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++fano_failures;
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if(Verbose)
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printf("trial %d fano: decode failure\n",trial);
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} else { // Fano finished, look for undetected errors
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errcnt = 0;
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for(i=0;i<Nbits/8;i++){
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int e;
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e = popcount(xordata[i] = decode_data[i] ^ data[i]);
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fano_bit_errors += e;
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errcnt += e;
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}
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if(errcnt != 0){
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fano_frame_errors++;
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fano_bit_errors += errcnt;
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if(Verbose)
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printf("trial %d fano: metric %ld, cycles %ld, bit errors %d\n",
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trial,metric,cycles,errcnt);
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if(Verbose > 1){
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for(i=0;i<Nbits/8;i++)
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printf("%02x",xordata[i]);
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putchar('\n');
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}
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} else {
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++fano_good_frames;
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if(Verbose > 1)
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printf("trial %d fano: metric = %ld, cycles %ld; data OK\n",trial,metric,cycles);
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continue; // Fano OK, next frame
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}
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}
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// Fano failed. Try Viterbi
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viterbi_attempts++;
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if(Verbose){
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printf("Trying Viterbi...");
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fflush(stdout);
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}
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if((vp = create_viterbi224(Nbits)) == NULL){
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printf("create_viterbi224 failed\n");
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exit(1);
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}
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init_viterbi224(vp,0); // Initialize Viterbi decoder
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update_viterbi224_blk(vp,symbols,Nbits); // Process symbols
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chainback_viterbi224(vp,decode_data,Nbits,0); // Viterbi chainback
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delete_viterbi224(vp);
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// look for Viterbi errors
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errcnt = 0;
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for(i=0;i<Nbits/8;i++){
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int e = popcount(xordata[i] = data[i] ^ decode_data[i]);
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errcnt += e;
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viterbi_bit_errors += e;
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}
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if(!errcnt){
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viterbi_good_frames++;
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if(Verbose)
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printf(" Success\n");
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continue;
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}
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// Viterbi made errors
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if(Verbose)
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printf(" %d bit errors\n",errcnt);
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viterbi_frame_errors++;
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viterbi_bit_errors += errcnt;
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if(Verbose > 1){
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for(i=0;i<Nbits/8;i++)
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printf("%02x",xordata[i]);
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putchar('\n');
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}
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}
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printf("Fano good frames: %d, decode failures %d, frame errors %d, bit errors %d cycles/bit %lf\n",
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fano_good_frames,fano_failures,fano_frame_errors,fano_bit_errors,(double)totcycles/(trial*Nbits));
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if(viterbi_attempts != 0){
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printf("Viterbi attempts %d good frames: %d frame errors %d (%lg%%) bit errors %d (%lg%%)\n",
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viterbi_attempts,
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viterbi_good_frames,viterbi_frame_errors,100.*viterbi_frame_errors/viterbi_attempts,
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viterbi_bit_errors,100.*viterbi_bit_errors/(Nbits*viterbi_attempts));
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}
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exit(0);
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}
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