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viterbi

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">  <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=windows-1252"> <META content="MSHTML 6.00.2900.2180" name=GENERATOR></HEAD> <BODY><PRE>// ------------------------------------------------------------------------ // File: viterbi_binary_hard.c // Date: April 1, 2002 // Description: Viterbi decoder, hard decision decoding. For a // rate-1/n convolutional code. Hamming metric. // // Maximum of 1024 states; max. truncation length = 1024 // // ------------------------------------------------------------------------ // This program is complementary material for the book: // // R.H. Morelos-Zaragoza, The Art of Error Correcting Coding, Wiley, 2002. // // ISBN 0471 49581 6 // // This and other programs are available at http://the-art-of-ecc.com // // You may use this program for academic and personal purposes only. // If this program is used to perform simulations whose results are // published in a journal or book, please refer to the book above. // // The use of this program in a commercial product requires explicit // written permission from the author. The author is not responsible or // liable for damage or loss that may be caused by the use of this program. // // Copyright (c) 2002. Robert H. Morelos-Zaragoza. All rights reserved. // ------------------------------------------------------------------------ #include <stdio.h> #include <math.h> #include <float.h> #include <limits.h> #include <time.h> #define MAX_RANDOM LONG_MAX // Use the compiling directive -DSHOW_PROGRESS to see how the decoder // converges to the decoded sequence by monitoring the survivor memory #ifdef SHOW_PROGRESS #define DELTA 1 #endif int k2=1, n2, m2; int NUM_STATES, OUT_SYM, NUM_TRANS; long TRUNC_LENGTH; double RATE; double INIT_SNR, FINAL_SNR, SNR_INC; long NUMSIM; FILE *fp, *fp_ber; int g2[10][10]; unsigned int memory2, output; /* Memory and output */ unsigned int data2; /* Data */ unsigned long seed; /* Seed for random generator */ unsigned int data_symbol[1024]; /* 1-bit data sequence */ long index; /* Index for memory management*/ double transmitted[10]; /* Transmitted signals/branch */ double snr, amp; double received[10]; /* Received signals/branch */ int fflush(); // Data structures used for trellis sections and survivors struct trel { int init; /* initial state */ int data; /* data symbol */ int final; /* final state */ double output[10]; /* output coded symbols (branch label) */ }; struct surv { double metric; /* metric */ int data[1024]; /* estimated data symbols */ int state[1024]; /* state sequence */ }; // A trellis section is an array of branches, indexed by an initial // state and a k_2-bit input data. The values read // are the final state and the output symbols struct trel trellis[1024][100]; /* A survivor is a sequence of states and estimated data, of length equal to TRUNC_LENGTH, together with its corresponding metric. A total of NUM_STATES survivors are needed */ struct surv survivor[1024], surv_temp[1024]; /* Function prototypes */ void encoder2(void); /* Encoder for C_{O2} */ int random_data(void); /* Random data generator */ void transmit(void); /* Encoder & BPSK modulator */ void awgn(void); /* Add AWGN */ void viterbi(void); /* Viterbi decoder */ double comp_metric(double rec, double ref); /* Metric calculator */ void open_files(void); /* Open files for output */ void close_files(void); /* Close files */ main(int argc, char *argv[]) { register int i, j, k; int init, data, final, output; register int error; unsigned long error_count; char name1[40], name2[40]; // Command line processing if (argc != 8) { printf("Usage %s file_input file_output truncation snr_init snr_final snr_inc num_sim\n", argv[0]); exit(0); } sscanf(argv[1],"%s", name1); sscanf(argv[2],"%s", name2); sscanf(argv[3],"%ld", &TRUNC_LENGTH); sscanf(argv[4],"%lf", &INIT_SNR); sscanf(argv[5],"%lf", &FINAL_SNR); sscanf(argv[6],"%lf", &SNR_INC); sscanf(argv[7],"%ld", &NUMSIM); printf("\nSimulation of Viterbi decoding over an AWGN channel with hard decisions\n"); printf("%ld simulations per Eb/No (dB) point\n", NUMSIM); fp_ber = fopen(name2,"w"); /* Open file with trellis data */ if (!(fp = fopen(name1,"r"))) { printf("Error opening file!\n"); exit(1); } fscanf(fp, "%d %d", &n2, &m2); RATE = 1.0 / (double) n2; fscanf(fp, "%d %d %d", &NUM_STATES, &OUT_SYM, &NUM_TRANS); for (j=0; j<n2; j++) fscanf(fp, "%x", &g2[j][0]); printf("\n%d-state rate-1/%d binary convolutional encoder\n", NUM_STATES, n2); printf("with generator polynomials "); for (j=0; j<n2; j++) printf("%x ", g2[j][0]); printf("\n"); printf("\n\nDecoding depth = %ld\n\n", TRUNC_LENGTH); /* =================== READ TRELLIS STRUCTURE ==================== */ for (j=0; j<NUM_STATES; j++) /* For each state in the section */ for (k=0; k<NUM_TRANS; k++) /* and for each outgoing branch */ { /* Read initial state, input data and final state */ fscanf(fp,"%d %d %d", &trellis[j][k].init, &trellis[j][k].data, &trellis[j][k].final); /* Read the output symbols of the branch */ for (i=0; i < OUT_SYM; i++) { fscanf(fp,"%d", &data); trellis[j][k].output[i] = (double) data; } } /* end for states */ /* end for branches */ fclose(fp); #ifdef PRINT for (j=0; j<NUM_STATES; j++) /* For each state in the section */ for (k=0; k<NUM_TRANS; k++) /* and for each outgoing branch */ { printf("%3d %3d %3d ", trellis[j][k].init, trellis[j][k].data, trellis[j][k].final); for (i=0; i < OUT_SYM; i++) printf("%2.0lf ", trellis[j][k].output[i]); printf("\n"); } /* end for states */ /* end for branches */ #endif snr = INIT_SNR; /* ======================== SNR LOOP ============================= */ while ( snr < (FINAL_SNR+1.0e-6) ) { amp = sqrt( 2.0 * RATE * pow(10.0, (snr/10.0)) ); /* Random seed from current time */ time(&seed); srandom(seed); /* Initialize transmitted data sequence */ for (i=0; i<TRUNC_LENGTH; i++) data_symbol[i]=0; /* Initialize survivor sequences and metrics */ for (i=0; i<NUM_STATES; i++) { survivor[i].metric = 0.0; /* Metric = 0 */ for (j=0; j<TRUNC_LENGTH; j++) { survivor[i].data[j] = 0; /* Estimated data = 0 */ survivor[i].state[j] = 0; /* Estimated state = 0 */ } } /* Index used in simulation loop */ index = 0; /* Initialize encoder memory */ memory2 = 0; /* Error counter */ error_count = 0; /* ===================== SIMULATION LOOP ========================= */ while (index < NUMSIM) { /* GENERATE a random bit */ data_symbol[index % TRUNC_LENGTH] = random_data(); /* */ /* ENCODE AND MODULATE (BPSK) data bit */ transmit(); /* ADD ADDITIVE WHITE GAUSSIAN NOISE */ awgn(); /* VITERBI DECODE */ viterbi(); index += 1; /* Increase simulation index */ /* COMPUTE ERRORS */ error = survivor[0].data[index %

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