📄 viterbi_qam.c
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#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include "random.h"
// make the complex structure
typedef struct complex1
{
double real;
double imag;
}complex;
// define the number of the iteration
#define ITERATION pow(10, 4)
#define THENUMBEROFDATA 1000
void convolution(int *data, int *codeddata);
double modulation(int data);
void demodulation(double * r_data);
int bercheck(int data, double d_data);
int comparison(int com1, int com2);
void viterbi_decode(int *d_data, int *decode_data);
void main()
{
FILE *fp1;
double Noisepower;
complex Noise;
int data[THENUMBEROFDATA];
int codeddata[2*(THENUMBEROFDATA+2)];
int cr_data[2];
int ci_data[2];
complex m_data;
complex r_data;
double d_datareal[2];
double d_dataimag[2];
int d_data[2*(THENUMBEROFDATA+2)];
int decode_data[THENUMBEROFDATA+2];
int error;
// int error1;
// int error2;
// int error3;
double avgerr;
int EbofN0;
// open and make the text file
fp1=fopen("result_16qam_Viterbi.txt","w");
srand(time(0));
for(EbofN0=11; EbofN0<=15; EbofN0+=1)
{
double sumerr=0.0;
int run;
int i;
int l;
for(run=0;run<ITERATION;run++)
{
// generate the real part data
generate_random(&data[0], THENUMBEROFDATA);
convolution(data, codeddata);
// generate the imaginary part data
//generate_random(&data1[0], THENUMBEROFDATA/2);
for (i=0; i<=(THENUMBEROFDATA/2);i++)
{
cr_data[0]=codeddata[4*i];
cr_data[1]=codeddata[4*i+1];
ci_data[0]=codeddata[4*i+2];
ci_data[1]=codeddata[4*i+3];
// modulated the real part signal
m_data.real = modulation(cr_data);
// modulated the imaginary part signal
m_data.imag = modulation(ci_data);
// make the noisepower
Noisepower=1/(2*pow(10,(double)EbofN0/10));
// make the real part of noise
Noise.real = sqrt(Noisepower/2)*GaussRand();
// make the imaginary part of noise
Noise.imag = sqrt(Noisepower/2)*GaussRand();
// receive the real part of the signal
r_data.real = sqrt(1.0/10.0)*m_data.real + Noise.real;
// receive the imaginary part of the signal
r_data.imag = sqrt(1.0/10.0)*m_data.imag + Noise.imag;
d_datareal[0] = r_data.real;
d_dataimag[0] = r_data.imag;
// demodulated the real part of the signal
demodulation(&d_datareal);
// demodulated the imaginary part of the signal
demodulation(&d_dataimag);
d_data[4*i]=(int)d_datareal[0];
d_data[4*i+1]=(int)d_datareal[1];
d_data[4*i+2]=(int)d_dataimag[0];
d_data[4*i+3]=(int)d_dataimag[1];
}
viterbi_decode(d_data,decode_data);
// check the error
for (l=0;l<=(THENUMBEROFDATA-1);l++)
{
//printf("%d=",decode_data[l]);
//printf("%d\n",data[l]);
error= bercheck(data[l], decode_data[l]);
sumerr = sumerr + error;
}
//error= bercheck(data[0], d_datareal[0]);
//error1= bercheck(data[1], d_datareal[1]);
//error2= bercheck(data1[0], d_dataimag[0]);
//error3= bercheck(data1[1], d_dataimag[1]);
//sumerr = sumerr + error + error1 + error2 + error3;
}
//calculated the BER
avgerr = sumerr / (ITERATION*THENUMBEROFDATA);
fprintf(fp1,"%.7f\n",avgerr);
printf("%.7f\n", avgerr);
}
fclose(fp1);
}
// modulation function
double modulation(int *data)
{
int m_data;
if (*data==1)
{
if(*(data+1)==1)
{
m_data=1;
}
else
{
m_data=3;
}
}
else
{
if(*(data+1)==1)
{
m_data=-1;
}
else
{
m_data=-3;
}
}
return (m_data);
}
// demodulation function
void demodulation(double *r_data)
{
if (r_data[0]>=0.0)
{
if (r_data[0]>=sqrt(1.0/10.0)*2.0)
{
r_data[0]=1;
r_data[1]=0;
}
else
{
r_data[0]=1;
r_data[1]=1;
}
}
else
{
if (r_data[0]<=sqrt(1.0/10.0)*(-2.0))
{
r_data[0]=0;
r_data[1]=0;
}
else
{
r_data[0]=0;
r_data[1]=1;
}
}
}
// error check function
int bercheck(int data, double d_data)
{
int error=0;
if ((double)data==d_data)
{
error=0;
}
else
{
error=1;
//printf("error occured\n");
}
return (error);
}
void convolution(int *data, int *codeddata)
{
int a = data[0];
int b = 0;
int c = 0;
int N =0;
//int codeddata[12];
for(N=0;N<=(THENUMBEROFDATA+1);N++)
{
codeddata[2*N] = a^b^c;
codeddata[2*N+1] = a^c;
a = data[N+1];
b = data[N];
if(N == 0)
{
c = 0;
}else
{
c = data[N-1];
}
if(N>=(THENUMBEROFDATA-1))
{
a=0;
}
if(N>=THENUMBEROFDATA)
{
b=0;
}
}
}
void viterbi_decode(int *d_data, int *decode_data)
{
int s[4][(THENUMBEROFDATA+3)];
int k1;
int k2;
int c[(THENUMBEROFDATA+2)];
int l1;
// int l2;
int i;
int l;
for (i = 0;i<=3;i++)
{
for(l=0;l<=THENUMBEROFDATA+2;l++)
{
s[i][l]=9;
}
}
s[0][0]=0;
s[0][1]=(d_data[0]^0)+(d_data[1]^0);
s[1][1]=(d_data[0]^1)+(d_data[1]^1);
s[0][2]=s[0][1]+(d_data[2]^0)+(d_data[3]^0);
s[1][2]=s[0][1]+(d_data[2]^1)+(d_data[3]^1);
s[2][2]=s[1][1]+(d_data[2]^1)+(d_data[3]^0);
s[3][2]=s[1][1]+(d_data[2]^0)+(d_data[3]^1);
for(k2=3;k2<=(THENUMBEROFDATA+2);k2++)
{
for(k1=0;k1<=3;k1++)
{
if(k1==0)
{
s[k1][k2]=comparison(s[k1][k2-1]+(d_data[2*(k2-1)]^0)+(d_data[2*(k2-1)+1]^0), s[k1+2][k2-1]+(d_data[2*(k2-1)]^1)+(d_data[2*(k2-1)+1]^1));
}
else if(k1==1)
{
s[k1][k2]=comparison(s[k1-1][k2-1]+(d_data[2*(k2-1)]^1)+(d_data[2*(k2-1)+1]^1), s[k1+1][k2-1]+(d_data[2*(k2-1)]^0)+(d_data[2*(k2-1)+1]^0));
}
else if(k1==2)
{
s[k1][k2]=comparison(s[k1-1][k2-1]+(d_data[2*(k2-1)]^1)+(d_data[2*(k2-1)+1]^0), s[k1+1][k2-1]+(d_data[2*(k2-1)]^0)+(d_data[2*(k2-1)+1]^1));
}
else if(k1==3)
{
s[k1][k2]=comparison(s[k1-2][k2-1]+(d_data[2*(k2-1)]^0)+(d_data[2*(k2-1)+1]^1), s[k1][k2-1]+(d_data[2*(k2-1)]^1)+(d_data[2*(k2-1)+1]^0));
}
}
}
if((s[0][(THENUMBEROFDATA+1)]+(d_data[2*(THENUMBEROFDATA+1)]^0)+(d_data[2*(THENUMBEROFDATA+1)+1]^0))==comparison(s[0][(THENUMBEROFDATA+1)]+(d_data[2*(THENUMBEROFDATA+1)]^0)+(d_data[2*(THENUMBEROFDATA+1)+1]^0) , s[2][(THENUMBEROFDATA+1)]+(d_data[2*(THENUMBEROFDATA+1)]^1)+(d_data[2*(THENUMBEROFDATA+1)+1]^1)))
{
c[(THENUMBEROFDATA+1)] = 0;
decode_data[(THENUMBEROFDATA-1)]=0;
}
else
{
c[(THENUMBEROFDATA+1)] = 2;
decode_data[(THENUMBEROFDATA-1)]=0;
}
for (l1=(THENUMBEROFDATA+1);l1>=1;l1--)
{
if (c[l1]==0)
{
if((s[0][l1-1]+(d_data[2*(l1-1)]^0)+(d_data[2*(l1-1)+1]^0))==comparison(s[0][l1-1]+(d_data[2*(l1-1)]^0)+(d_data[2*(l1-1)+1]^0),s[2][l1-1]+(d_data[2*(l1-1)]^1)+(d_data[2*(l1-1)+1]^1)))
{
c[l1-1] = 0;
decode_data[l1-1]=0;
}
else
{
c[l1-1] = 2;
decode_data[l1-1]=0;
}
}else if(c[l1]==1)
{
if((s[0][l1-1]+(d_data[2*(l1-1)]^1)+(d_data[2*(l1-1)+1]^1))==comparison(s[0][l1-1]+(d_data[2*(l1-1)]^1)+(d_data[2*(l1-1)+1]^1),s[2][l1-1]+(d_data[2*(l1-1)]^0)+(d_data[2*(l1-1)+1]^0)))
{
c[l1-1] = 0;
decode_data[l1-1]=1;
}
else
{
c[l1-1] = 2;
decode_data[l1-1]=1;
}
}else if(c[l1]==2)
{
if((s[1][l1-1]+(d_data[2*(l1-1)]^1)+(d_data[2*(l1-1)+1]^0))==comparison(s[1][l1-1]+(d_data[2*(l1-1)]^1)+(d_data[2*(l1-1)+1]^0),s[3][l1-1]+(d_data[2*(l1-1)]^0)+(d_data[2*(l1-1)+1]^0)))
{
c[l1-1] = 1;
decode_data[l1-1]=0;
}
else
{
c[l1-1] = 3;
decode_data[l1-1]=0;
}
}else if(c[l1]==3)
{
if((s[1][l1-1]+(d_data[2*(l1-1)]^0)+(d_data[2*(l1-1)+1]^1))==comparison(s[1][l1-1]+(d_data[2*(l1-1)]^0)+(d_data[2*(l1-1)+1]^1),s[3][l1-1]+(d_data[2*(l1-1)]^1)+(d_data[2*(l1-1)+1]^0)))
{
c[l1-1] = 1;
decode_data[l1-1]=1;
}
else
{
c[l1-1] = 3;
decode_data[l1-1]=1;
}
}
}
/*
for(l=0;l<=THENUMBEROFDATA+1;l++)
{
printf("%d ",c[l]);
}
printf("\n");
for(i=0;i<=3;i++)
{
for(l=0;l<=THENUMBEROFDATA+2;l++)
{
printf("%d",s[i][l]);
}
printf("\n");
}*/
}
int comparison(int com1, int com2)
{
int com3;
if(com1>=com2)
{
com3=com2;
}else
{
com3=com1;
}
return (com3);
}
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