// ------------------------------------------------------------------------
// File: bound_awgn_ebno.c
//
// Union bound on the probability of a bit error for a linear code
// with soft-decision decoding and binary transmission over an
// AWGN channel
// ------------------------------------------------------------------------
// 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>

main(argc,argv)
int argc;
char **argv;
{
  double delta1,delta2,nn,nn2,nn3;   
  
  int    iter,i,i1,j,n,k,k2,k3,dimension,n_max,n_max2,n_max3;
  double ii1,init,final,inc,eb_no_db,es_no,P1,P2;
  double sum,sum1,sum2,sum3,aux,beta,rate,c1,jaux,d12;
  
  int d_hi[64];
  double d_h[64],n_d[64];
  int d_hi2[64];
  double d_h2[64],n_d2[64];
  char name1[40],name2[40];   
  int d_hi3[64];
  double d_h3[64],n_d3[64];
  
  double Q(double a);
  double erfc( double x );
  
  FILE *fp,*fp1,*fp2,*fp11,*fp22,*fp33;
  
    if (argc != 8)
  {
    printf("Usage: %s n k wdfile file_bound   init_SNR  final_SNR  inc_SNR\n",
    argv[0]);
    exit(1);
  }
  sscanf(argv[1], "%d", &n);
  sscanf(argv[2], "%d", &k);
  sscanf(argv[3], "%s", name1);
  sscanf(argv[4], "%s", name2);
  sscanf(argv[5], "%lf", &init);
  sscanf(argv[6], "%lf", &final);
  sscanf(argv[7], "%lf", &inc);

  rate = (double) k / (double) n;
  fp1 = fopen(name1,"r");
  fp11 = fopen(name2,"w");
  
  n_max = 0;
  while(fscanf(fp1,"%d %lf\n",&d_hi[n_max],&n_d[n_max])!=EOF)
    {
      n_max++;
    }
  
  fclose(fp1);
  
#ifdef DEBUG
  printf("Weight distribution (scrambled):\n");
  for (i=0; i<n_max; i++)
    printf("%d %lf\n", d_hi[i], n_d[i]);
#endif
  
  printf("\nEb/No \tPb\n");
  
  for (i=0;i<n_max;i++)
    d_h[i] = (double) d_hi[i];
  
  /* Compute the union bound */
  
  for (eb_no_db = init; eb_no_db<=final; eb_no_db+=inc)
    {
      es_no = pow(10.0,(eb_no_db/10.0));   /* snr per bit */
      es_no = es_no*rate;                  /* snr per symbol */
      
      sum = 0.0;
      
      for (i=0;i<n_max;i++)
	{
          // sum += ( (d_h[i]/n) * n_d[i]  // <---  Uncomment this for Pb
          sum += ( n_d[i]            // <---  Uncomment this for Pe
			      * Q ( sqrt( 2.0 *  es_no * d_h[i] ) ) );          
	}
      
      printf("%lf\t%e\n",eb_no_db,sum);
      fprintf(fp11,"%lf\t%e\n",eb_no_db,sum);
      
    }
  
}


double Q(double a)
{
	double erfc( double x );
    return(0.5*erfc(a/sqrt(2.0)));
}