channel.h

软判决功率归一viterbi约束长度9

#include <math.h>
#define PI 3.14159

struct    AWGN
{
	long      reset;
	long      ix;
	long      iy;
	long      iz;
	double     snr;
	double     sigma;
	double     I_sigma;      //(1/(sigma*sigma))
	double     rate;
};

 double random_u(struct AWGN *gauss)
 { 
    double temp;
    gauss->ix = (gauss->ix*249) % 61967; 
    gauss->iy = (gauss->iy*251) % 63443;
    gauss->iz = (gauss->iz*252) % 63599;
    temp= ( (double)gauss->ix/(double)61967 + (double)gauss->iy/(double)63443+ (double)gauss->iz/(double)63599 )
	   -(int)( (double)gauss->ix/(double)61967+ (double)gauss->iy/(double)63443+(double)gauss->iz/(double)63599 );
    return(temp);     
}

 double gauss_g(struct AWGN *gauss)
 {
    double u1,u2;
    double x;
    double var;
    var = gauss->sigma;
    u1=random_u(gauss);
    u2=random_u(gauss);
    x=(double)sqrt((double)(-2)*log((double)1-u1))*(double)cos((double)2*(double)PI*u2);
    x=(double)var*x; /*** 常数系数指标准差 ***/
    return(x);
}


 void awgn_channel (int input[] , double output[] , struct AWGN *gauss , int len)
 {
	int i;
	double add;
	int COLUMN;
	COLUMN = len;
	for (i=0;i<COLUMN;i++)
	{
	    add = gauss_g(gauss);
	    output[i] = input[i] + add;
	}
}