// ------------------------------------------------------------------------
//        File: tcm_8psk.c
//        Date: April 2, 2002.
// Description: TCM decoder, maximum likelihood decoding. 
// ------------------------------------------------------------------------
// 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 explicitely 
// 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 "viterbi_conventional.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;

char name1[40], name2[40];
FILE  *fp;                 /* Pointer for trellis data file */

//  unsigned int g2[n2][k2] =  { /* rate-1/2 memory=6 */
//          0x4f, /* REVERSE ORDER */
//          0x6d }; /* */

unsigned 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 */
unsigned int data_symbol2[1024];  /* 1-bit data sequence */
unsigned long indxx;                     /* Simulation index */

double psk_I[8], psk_Q[8];

int transmitted;                  /* index of transmitted signal */
double transmitted_I;             /* Transmitted signals/branch */
double transmitted_Q;             /* Transmitted signals/branch */
int estimate_data2;

double snr, amp;

double received_I;                       /* Received signals/branch */
double received_Q;                       /* Received signals/branch */

// Data structures used for trellis sections and survivors
struct trel {
  int init;                /* initial state */
  int data;                /* data symbol */
  int final;               /* final state */
  int output;  /* output coded symbols (branch label) */
}; 
struct surv {
  double metric;           /* metric */
  int data[1024];  /* estimated data symbols */
  int data2[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_I, double rec_Q, int ref); /* Metric calc */
double comp_correl(double rec_I, double rec_Q, int ref); /* Metric calc */
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, error_coded, error_uncoded;
  FILE  *fp_ber;             /* Pointer for overall BER data file */
  double RATE;

  // 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 TCM decoding with 8-PSK modulation over an AWGN channel\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 = (2.0 / (double) n2)*3.0;  // 2 bits per symbol if encoder is rate 1/2

  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("\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 */
		fscanf(fp,"%d", &data);
		trellis[j][k].output = data;
	  } /* end for states */
    /* end for branches */
      
  fclose(fp);
      
#ifdef PRI
  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);
	    printf("%d", trellis[j][k].output);
	    printf("\n");
	  } /* end for states */
      /* end for branches */
#endif

  snr = INIT_SNR;

  /* Bits-to-8PSK signal mapping as used in Japanese Satellite ISDB

                                |
                        [3] 011 #
                                |
                   [2] 010 $    |    * 001 [1]
                                |
                [4] 100         |         000 [0]
                   -----+---------------+-----
                                |
                                |
                   [5] 101 *    |    $ 110 [6]
                                |
                                # 111 [7]
                                |

   */

  /* Coordinates of the 8-PSK symbols */

  psk_I[0] = 1.0;              psk_Q[0] = 0.0;
  psk_I[1] = cos(M_PI/4.0);    psk_Q[1] = sin(M_PI/4.0);
  psk_I[3] = 0.0;              psk_Q[3] = 1.0;
  psk_I[2] = -cos(M_PI/4.0);   psk_Q[2] = sin(M_PI/4.0);
  psk_I[4] = -1.0;             psk_Q[4] = 0.0;
  psk_I[5] = -cos(M_PI/4.0);   psk_Q[5] = -sin(M_PI/4.0);
  psk_I[7] = 0.0;              psk_Q[7] = -1.0;
  psk_I[6] = cos(M_PI/4.0);    psk_Q[6] = -sin(M_PI/4.0);

/***** Try this:
  psk_I[0] = cos(M_PI/8.0);        psk_Q[0] = sin(M_PI/8.0);
  psk_I[1] = cos(3.0*M_PI/8.0);    psk_Q[1] = sin(3.0*M_PI/8.0);
  psk_I[3] = -cos(3.0*M_PI/8.0);   psk_Q[3] = sin(3.0*M_PI/8.0);
  psk_I[2] = -cos(M_PI/8.0);       psk_Q[2] = sin(M_PI/8.0);
  psk_I[4] = -cos(M_PI/8.0);       psk_Q[4] = -sin(M_PI/8.0);
  psk_I[5] = -cos(3.0*M_PI/8.0);   psk_Q[5] = -sin(3.0*M_PI/8.0);
  psk_I[7] = cos(3.0*M_PI/8.0);    psk_Q[7] = -sin(3.0*M_PI/8.0);
  psk_I[6] = cos(M_PI/8.0);        psk_Q[6] = -sin(M_PI/8.0);
******/

  /* ======================== SNR LOOP ============================= */

  while ( snr < (FINAL_SNR+0.001) )

    {

#ifdef PRINT
  printf("Viterbi decoding of a rate-1/n convolutional code\n");
#endif

      /* Random seed from current time */
      time(&seed);
      srandom(seed);

      amp = sqrt(2.0*RATE*pow(10.0,(snr/10.0)));

      /* Initialize transmitted data sequence */
      
      for (i=0; i<TRUNC_LENGTH; i++)
        {
          data_symbol[i]=0;
          data_symbol2[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].data2[j] = 0;       /* Estimated (uncoded) data = 0 */
	      survivor[i].state[j] = 0;       /* Estimated state = 0 */
	    }
	}
      
      /* Index used in simulation loop */

      indxx = 0;
      
      /* Initialize encoder memories */

      memory2 = 0;

      /* Error counters */

      error_count = error_coded = error_uncoded = 0;


      /* ===================== SIMULATION LOOP ========================= */
      
      while (indxx < NUMSIM) 

        { 
	
          /* GENERATE random two-bit symbols */
	  
      i = random_data();
	  data_symbol[indxx % TRUNC_LENGTH] = (i & 1); /* */
	  data_symbol2[indxx % TRUNC_LENGTH] = ( (i>>1) & 1 ); /* */
	  
#ifdef PRINT
	  printf("Transmitted data sequence:\n");
	  printf("%2d %x   ",(indxx % TRUNC_LENGTH),
		 data_symbol[indxx % TRUNC_LENGTH]);
	  for (i=0; i<TRUNC_LENGTH; i++)
	    printf("%x", data_symbol[i]);
	  printf("\n");
#endif
	  
	  /* ENCODE AND MODULATE (BPSK) data bit */
	  
	  transmit();
	  
#ifdef PRI
	  printf("Transmitted = ");
	  printf("%d ", transmitted);
	  printf("\n");
#endif
	  
	
	  /* ADD ADDITIVE WHITE GAUSSIAN NOISE */
	  
	  awgn(); /* */
	  

	  /* VITERBI DECODE */
	  
	  viterbi();
	  
	  indxx += 1;           /* Increase simulation index */
	  
	  /* COMPUTE ERRORS */
	  
	  error = survivor[0].data[indxx % TRUNC_LENGTH]
	          ^ data_symbol[indxx % TRUNC_LENGTH]; 

	  error += survivor[0].data2[indxx % TRUNC_LENGTH]
	          ^ data_symbol2[indxx % TRUNC_LENGTH]; 

	  if (error)
	    error_count+=error;
	  

      error_coded += (survivor[0].data[indxx % TRUNC_LENGTH]
                                     ^ data_symbol[indxx % TRUNC_LENGTH]);
      error_uncoded += (survivor[0].data2[indxx % TRUNC_LENGTH]
                                     ^ data_symbol2[indxx % TRUNC_LENGTH]);

#ifdef SHOW_PROGRESS
	  
	  if ( (indxx % DELTA) == 0 )
	    {
          printf("index = %ld\n", indxx);
	      for (i=0; i<TRUNC_LENGTH; i++)
		    printf("%x", survivor[0].data[i]);
	      printf("\nErrors = %ld %ld %ld\n", error_count, error_coded,
                 error_uncoded);
	    }
	  
#endif
	  
	}
      
      printf("%f  %10.4e\n",snr, ((double) error_count/((double) indxx*2.0) ) );

      fprintf(fp_ber, "%f %20.15f\n", snr,
	       ((double) error_count / ((double) indxx*2.0) ) );

      fflush(stdout);
      fflush(fp_ber);

      snr += SNR_INC;

    }
  
  fclose(fp_ber);

  return 0;

}



/****************************************************************************/

int random_data()
{
  /* Random two-bit number generator */

  return( (random() >> 5) & 3 );
}



/****************************************************************************/

void encoder2()
{
  /* Conventional convolutional encoder, rate 1/n2 (fixed k_2=1) */
  register int i, j, result, temp;
  
  temp = memory2;
  output = 0;

 temp = (temp<<1) ^ data_symbol[indxx % TRUNC_LENGTH];

  for (i=0; i<n2; i++)
   {
     result = 0;
     for (j=m2; j>=0; j--)
       result ^= ( ( temp & g2[i][0] ) >> j ) & 1;
     output = ( output<<1 ) ^ result;
   }

  memory2 = temp ;
}



/****************************************************************************/

void transmit()
{
  /* Encode and modulate a 1-bit data sequence */
  int i;

  encoder2(); /* */

#ifdef DEB
  printf("memory2 = %x\n", memory2);
#endif

  transmitted = output + 4*data_symbol2[indxx % TRUNC_LENGTH];

}



/****************************************************************************/

void awgn()
{
  /* Add AWGN to transmitted sequence */
  double u1,u2,s,noise,randmum;
  int i;

#ifdef PRINT
      printf("Received    = ");
#endif

#ifdef NO_NOISE
    received_I = psk_I[transmitted];
    received_Q = psk_Q[transmitted];
    return;
}
#else
      do
	{	
	  randmum = (double)(random())/MAX_RANDOM;
	  u1 = randmum*2.0 - 1.0;
	  randmum = (double)(random())/MAX_RANDOM;
	  u2 = randmum*2.0 - 1.0;
	  s = u1*u1 + u2*u2;
	} while( s >= 1);

      noise = u1 * sqrt( (-2.0*log(s))/s )/amp;
      received_I = psk_I[transmitted] + noise;

      do
    {
      randmum = (double)(random())/MAX_RANDOM;
      u1 = randmum*2.0 - 1.0;
      randmum = (double)(random())/MAX_RANDOM;
      u2 = randmum*2.0 - 1.0;
      s = u1*u1 + u2*u2;
    } while( s >= 1);

      noise = u1 * sqrt( (-2.0*log(s))/s )/amp;
      received_Q = psk_Q[transmitted] + noise;

#ifdef PRINT
      printf("%4.2lf %4.2lf ", received_I, received_Q);
#endif

#ifdef PRINT
      printf("\n");
#endif

}
#endif



/****************************************************************************/

void viterbi()
{ /* Viterbi decoding */

  double aux_metric, surv_metric[NUM_STATES];
  register int i,j,k;
  double metrics[4];
  int estimated[4];

  /* Branch metric computation and uncoded bit */
  for (i=0; i<4; i++)
    {
      metrics[i] = comp_metric(received_I,received_Q,i);
      estimated[i] = estimate_data2;
    }

  for (i=0; i<NUM_STATES; i++) /* Initialize survivor branch metric */
    surv_metric[i] = DBL_MAX;

  for (i=0; i<NUM_STATES; i++) /* Loop over inital states */
    {

    for (j=0; j<NUM_TRANS; j++) /* Loop over data */
      {

	  /* Compute metric between received and coded symbols */
/**
      aux_metric = comp_metric(received_I,received_Q,trellis[i][j].output);
	  aux_metric += survivor[i].metric;
 **/
      aux_metric = survivor[i].metric + metrics[trellis[i][j].output];

#ifdef PRINT
	  printf("rec_I   rec_Q  index_coded\n");
	  printf("%6.2lf %6.2lf %d\n", received_I,received_Q,trellis[i][j].output);
	  printf("init, data, final, metric = %2d %2d %2d %lf\n", i, j,
		 trellis[i][j].final, aux_metric);
#endif

	  /* compare with survivor metric at final state */
          if ( aux_metric < surv_metric[trellis[i][j].final] )

	    { /* Good candidate found */

	      surv_metric[trellis[i][j].final] = aux_metric;

	      /* Update data and state paths */
	      for (k=0; k<TRUNC_LENGTH; k++)
		{
		  surv_temp[trellis[i][j].final].data[k] =
		    survivor[i].data[k];
		  surv_temp[trellis[i][j].final].data2[k] =
		    survivor[i].data2[k];
		  surv_temp[trellis[i][j].final].state[k] =
		    survivor[i].state[k];
		}
#ifdef PRINT
printf("estimate_data2 = %d\n", estimate_data2);
#endif
		  surv_temp[trellis[i][j].final].data[indxx%TRUNC_LENGTH] = j;
/**
		  surv_temp[trellis[i][j].final].data2[indxx%TRUNC_LENGTH] = estimate_data2;
**/
          surv_temp[trellis[i][j].final].data2[indxx%TRUNC_LENGTH] = estimated[trellis[i][j].output];
		  surv_temp[trellis[i][j].final].state[indxx%TRUNC_LENGTH] = 
		    trellis[i][j].final;
	    }
      }
    }
  
  for (i=0; i<NUM_STATES; i++)
    {
      /* Update survivor metrics */
      survivor[i].metric = surv_metric[i];
      for (k=0; k<TRUNC_LENGTH; k++)
        {
          survivor[i].data[k] = surv_temp[i].data[k];
          survivor[i].data2[k] = surv_temp[i].data2[k];
          survivor[i].state[k] = surv_temp[i].state[k];
        }
    }
  
#ifdef PRINT
  for (i=0; i<NUM_STATES; i++)
    {
      printf("survivor %2d, initial state = %2d metric = %10.5lf, ", i,
	     survivor[i].state[(indxx-1) % TRUNC_LENGTH], survivor[i].metric);
      printf("\t estimate = %d\n", survivor[i].data[indxx % TRUNC_LENGTH]);
    }
  printf("\n");
#endif
#ifdef DEBUG
  printf("Surviving paths (data):\n");
   for (i=0; i<NUM_STATES; i++)
     {
       printf("%2d --> ",i);
       for (k=0; k<TRUNC_LENGTH; k++)
	 printf("%1x", survivor[i].data[k]);
       printf("\n");
     }
  printf("\n");
#endif

}



/****************************************************************************/

double comp_metric(double rec_I, double rec_Q, int ref)
{ /* Gaussian metric between received and reference symbols */

  double aux, aux2;

#ifdef ABS
  /* Uncoded bit = 0 */
  aux = fabs(rec_I-psk_I[ref]) + fabs(rec_Q-psk_Q[ref]);
  /* Uncoded bit = 1 */
  aux2 = fabs(rec_I-psk_I[ref+4]) + fabs(rec_Q-psk_Q[ref+4]);
#else
  /* Uncoded bit = 0 */
  aux = ( (rec_I-psk_I[ref])*(rec_I-psk_I[ref]) 
                         + (rec_Q-psk_Q[ref])*(rec_Q-psk_Q[ref]) );
  /* Uncoded bit = 1 */
  aux2 =( (rec_I-psk_I[ref+4])*(rec_I-psk_I[ref+4]) 
                         + (rec_Q-psk_Q[ref+4])*(rec_Q-psk_Q[ref+4]) );
#endif

  if (aux < aux2)
    {
      estimate_data2 = 0;
      return(aux);
    }
  else
    {
      estimate_data2 = 1;
      return(aux2);
    }

}



/****************************************************************************/

double comp_correl(double rec_I, double rec_Q, int ref)
{ /* Gaussian metric between received and reference symbols */

  double aux, aux2;

  /* Uncoded bit = 0 */
  aux = - ( rec_I*psk_I[ref] + rec_Q*psk_Q[ref] );
                         
  /* Uncoded bit = 1 */
  aux2 = - ( rec_I*psk_I[ref+4] + rec_Q*psk_Q[ref+4] );

  if (aux < aux2)
    {
      estimate_data2 = 0;
      return(aux);
    }
  else
    {
      estimate_data2 = 1;
      return(aux2);
    }

}