hard_decodemex2.c

本程序利用改进的CHOW算法

/* Convolutional Decoder
   pass in generating polynomials g m-by-3 (m=1 to 7)
   outputs decoded bitstream
   written by Joe Williams - Southern Methodist University as ugrad,
   now Stanford grad student in EE.
   if you use this, you must give the author proper credit
*/

#include "mex.h"
#include "mat.h"
#include <math.h>
#define  decode_out plhs[0]
#define	g_in prhs[0]
#define	code_in prhs[1]

void mexFunction(int nlhs, 
                     mxArray *plhs[],
                     int nrhs, 
                     const mxArray *prhs[])
    {
       
double *code,*decode;
bool g[7][3];
int n,j,k,length,true_length,i,col,row,num_zeros,num_ones,index;

n = mxGetM(g_in);//get the size of the g matrix 
k = mxGetN(g_in);
length = mxGetN(code_in);
true_length = (length - 2*n)/n;
for(col=0;col<k;col++){//Create a c-matrix
  for(row=0;row<n;row++){
	g[row][col]=(mxGetPr(g_in))[row+col*mxGetM(g_in)];
  }
}

if(n==5) index=3;//set up number of 1 1 1's in g matrix for large g
else if(n==6) index=4;
else if(n==7) index=4;

code = mxGetPr(code_in);
decode_out = mxCreateDoubleMatrix(1,true_length, mxREAL);
decode = mxGetPr(decode_out);
num_zeros = 0;
num_ones = 0;
//decode[0] = code[0];
for(i=0;i<n;i++){
  num_zeros += 1-code[i];
  num_ones += code[i];
}
if(num_zeros>num_ones)
  decode[0] = 0;
else
  decode[0] = 1;
if(true_length>1){
  num_zeros = 0;
  num_ones = 0;
  if((g[0][0]==1)&&(g[0][1]==0)&&(g[0][2]==1)){
    //decode[1]=code[n];
    num_zeros += 1-code[n];
    num_ones += code[n];
    for(i=n+1;i<2*n;i++){
	  if((!decode[0])&&(!code[i])) num_zeros += 1;
	  else if((decode[0])&&(code[i])) num_zeros += 1;
	  else if((!decode[0])&&(code[i]))num_ones +=1;
	  else if((decode[0])&&(!code[i]))num_ones +=1;
    }
    if(num_zeros>num_ones)
      decode[1]=0;
    else
      decode[1]=1;
    for(i=1;i<=true_length-2;i++){
      //if(code[(i+1)*n]==0)
      //  decode[i+1]=decode[i-1];
      //else
      //  decode[i+1]=-1*decode[i-1]+1;
      num_zeros = 0;
      num_ones = 0;
      //num_zeros += 1-(code[(i+1)*n])*(!decode[i-1]);//1 0 1 part
      if((!code[(i+1)*n])&&(!decode[i-1])) num_zeros++;
      else if((!code[(i+1)*n])&&(decode[i-1])) num_ones++;
      else if((code[(i+1)*n])&&(decode[i-1])) num_zeros++;
      else if((code[(i+1)*n])&&(!decode[i-1])) num_ones++;
      //num_ones += (code[(i+1)*n])*(!decode[i-1]);
    for(j=(i+1)*n+1;j<(i+2)*n;j++){
	  if((!decode[i-1])&&(!decode[i])&&(!code[j])) num_zeros += 1;
	  else if((!decode[i-1])&&(!decode[i])&&(code[j])) num_ones += 1;
	  else if((!decode[i-1])&&(decode[i])&&(!code[j])) num_ones +=1;
	  else if((!decode[i-1])&&(decode[i])&&(code[j])) num_zeros +=1;
	  else if((decode[i-1])&&(!decode[i])&&(!code[j])) num_ones +=1;
	  else if((decode[i-1])&&(!decode[i])&&(code[j])) num_zeros +=1;
	  else if((decode[i-1])&&(decode[i])&&(!code[j])) num_zeros +=1;
	  else if((decode[i-1])&&(decode[i])&&(code[j])) num_ones +=1;
    }
    if(num_zeros>num_ones)
      decode[i+1]=0;
    else
      decode[i+1]=1;
    }
  }
  else{
    //decode[1]=code[2*n-1];
    for(i=n;i<2*n;i++){
	  if(i<index+n){
	    if((!decode[0])&&(!code[i])) num_zeros += 1;
	    else if((decode[0])&&(code[i])) num_zeros += 1;
	    else if((!decode[0])&&(code[i]))num_ones +=1;
	    else if((decode[0])&&(!code[i]))num_ones +=1;
	  }
	  else{
	    num_zeros += 1-code[i];
	    num_ones += code[i];
	  }
    }
    if(num_zeros>num_ones)
      decode[1]=0;
    else
      decode[1]=1;
    for(i=1;i<=true_length-2;i++){
      //if(code[(i+1)*n+n-1]==0)
      //  decode[i+1]=decode[i-1];
      //else
      //  decode[i+1]=-1*decode[i-1]+1;
      num_zeros = 0;
      num_ones = 0;
      for(j=(i+1)*n;j<(i+2)*n;j++){
        if((j%n)<index){
          if((!decode[i-1])&&(!decode[i])&&(!code[j])) num_zeros += 1;
	      else if((!decode[i-1])&&(!decode[i])&&(code[j])) num_ones += 1;
    	  else if((!decode[i-1])&&(decode[i])&&(!code[j])) num_ones +=1;
          else if((!decode[i-1])&&(decode[i])&&(code[j])) num_zeros +=1;
     	  else if((decode[i-1])&&(!decode[i])&&(!code[j])) num_ones +=1;
	      else if((decode[i-1])&&(!decode[i])&&(code[j])) num_zeros +=1;
    	  else if((decode[i-1])&&(decode[i])&&(!code[j])) num_zeros +=1;
	      else if((decode[i-1])&&(decode[i])&&(code[j])) num_ones +=1;
        }
        else{
          if((!code[j])&&(!decode[i-1])) num_zeros++;
          else if((!code[j])&&(decode[i-1])) num_ones++;
          else if((code[j])&&(decode[i-1])) num_zeros++;
          else if((code[j])&&(!decode[i-1])) num_ones++;
        }
      }
      if(num_zeros>num_ones)
        decode[i+1]=0;
      else
        decode[i+1]=1;
    }
  }
}
}