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Viterbi.c
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Viterbi.c
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#include "stm32f4xx.h"
#include<string.h>
#include "Viterbi.h"
void To_Binary(int n, int binaryNum[] )
{
// counter for binary array
int i = 0 ;
while (n > 0)
{
// storing remainder in binary array
binaryNum[i] = n % 2;
n = n / 2;
i++;
}
}
void int_to_bin_digit(unsigned int in, int count, int* out)
{
/* assert: count <= sizeof(int)*CHAR_BIT */
unsigned int mask = 1U << (count-1);
int i;
for (i = 0; i < count; i++) {
out[i] = (in & mask) ? 1 : 0;
in <<= 1;
}
}
void Viterbi(int SIZE_V, int *Conv_output,int *Output_Data )
{
int N = SIZE_V/4; // SIZE_V size of input data
int Input_Data[SIZE_V];
unsigned int i,j,k;
int binaryNum[4] ;
int binary[4] ;
int Branch_Metric[16][SIZE_V];
int Metric[16][SIZE_V] ;
int Path_Metric[16][SIZE_V];
for(j = 0;j < SIZE_V;j++)
{
if(Conv_output[j] == 1){Input_Data[j]= -1;}
else {Input_Data[j]= 1;}
}
// Euclidean distance function
for(i = 0;i <4;i++) // FOR STAGE 1 TO 4
{
for(k = 0;k < 16;k++)
{
int_to_bin_digit(k, 4, binaryNum);
for(j = 0;j < 4;j++)
{
if (binaryNum[j]==1) {binary[j]=-1;}
else {binary[j]=1;}
}
Branch_Metric[k][i] =binary[0]*Input_Data[4*i] + binary[1]*Input_Data[4*i+1] + binary[2]*Input_Data[4*i+2] + binary[3]*Input_Data[4*i+3]; // Euclidean distance computation
}
// STAGE 1
Metric[0][1] = Branch_Metric[0][0];
Metric[8][1] = Branch_Metric[15][0];
Path_Metric[0][1] =Path_Metric[8][1] = 0;
// STAGE 2
Metric[0][2] = Branch_Metric[0][1] + Metric[0][1];
Metric[8][2] = Branch_Metric[15][1] + Metric[0][1];
Metric[4][2] = Branch_Metric[12][1] + Metric[8][1];
Metric[12][2] = Branch_Metric[3][1] + Metric[8][1];
Path_Metric[0][2] =Path_Metric[8][2] = 0;
Path_Metric[4][2]=Path_Metric[12][2] = 8;
// STAGE 3
Metric[0][3] = Branch_Metric[0][2] + Metric[0][2];
Metric[8][3] = Branch_Metric[15][2] + Metric[0][2];
Metric[4][3] = Branch_Metric[12][2] + Metric[8][2];
Metric[12][3] = Branch_Metric[3][2] + Metric[8][2];
Path_Metric[0][3] =Path_Metric[8][3] = 0;
Path_Metric[4][3]=Path_Metric[12][3] = 8;
Metric[2][3] = Branch_Metric[10][2] + Metric[4][2];
Metric[10][3] = Branch_Metric[5][2] + Metric[4][2];
Path_Metric[2][3] = Path_Metric[10][3]= 4;
Metric[6][3] = Branch_Metric[6][2] + Metric[12][2];
Metric[14][3] = Branch_Metric[1][2] + Metric[12][2];
Path_Metric[6][3] = Path_Metric[14][3]= 12;
// STAGE 4
Metric[0][4] = Branch_Metric[0][3] + Metric[0][3];
Path_Metric[0][4]= 0;
Metric[1][4] = Branch_Metric[13][3] + Metric[2][3];
Path_Metric[1][4]= 2;
Metric[2][4] = Branch_Metric[10][3] + Metric[4][3];
Path_Metric[2][4]= 4;
Metric[3][4] = Branch_Metric[7][3] + Metric[6][3];
Path_Metric[3][4]= 6;
Metric[4][4] = Branch_Metric[12][3] + Metric[8][3];
Path_Metric[4][4]= 8;
Metric[5][4] = Branch_Metric[1][3] + Metric[10][3];
Path_Metric[5][4]= 10;
Metric[6][4] = Branch_Metric[6][3] + Metric[12][3];
Path_Metric[6][4]= 12;
Metric[7][4] = Branch_Metric[11][3] + Metric[14][3];
Path_Metric[7][4]= 14;
Metric[8][4] = Branch_Metric[15][3] + Metric[0][3];
Path_Metric[8][4]= 0;
Metric[9][4] = Branch_Metric[2][3] + Metric[2][3];
Path_Metric[9][4]= 2;
Metric[10][4] = Branch_Metric[5][3] + Metric[4][3];
Path_Metric[10][4]= 4;
Metric[11][4] = Branch_Metric[14][3] + Metric[6][3];
Path_Metric[11][4]= 6;
Metric[12][4] = Branch_Metric[3][3] + Metric[8][3];
Path_Metric[12][4]= 8;
Metric[13][4] = Branch_Metric[14][3] + Metric[10][3];
Path_Metric[13][4]= 10;
Metric[14][4] = Branch_Metric[1][3] + Metric[12][3];
Path_Metric[14][4]= 12;
Metric[15][4] = Branch_Metric[4][3] + Metric[14][3];
Path_Metric[15][4]= 14;
} // END OF STAGE 1 TO 4
//----------------------------- FOR STAGE 5 TO N
i =4;
while(i < N)
{
for(k = 0;k < 16;k++)
{
int_to_bin_digit(k, 4, binaryNum);
for(j = 0;j < 4;j++)
{
if (binaryNum[j]==1) {binary[j]=-1;}
else {binary[j]=1;}
}
Branch_Metric[k][i] =binary[0]*Input_Data[4*i] + binary[1]*Input_Data[4*i+1] + binary[2]*Input_Data[4*i+2] + binary[3]*Input_Data[4*i+3]; // Euclidean distance computation
}
Metric[0][i+1] = ((Metric[0][i] + Branch_Metric[0][i]) > (Metric[1][i] + Branch_Metric[15][i]))? (Metric[0][i] + Branch_Metric[0][i]):(Metric[1][i] + Branch_Metric[15][i]);
Path_Metric[0][i+1] = ((Metric[0][i] + Branch_Metric[0][i]) > (Metric[1][i] + Branch_Metric[15][i]))? 0:1;
Metric[1][i+1] = ((Metric[2][i] + Branch_Metric[13][i]) > (Metric[3][i] + Branch_Metric[2][i]))? (Metric[2][i] + Branch_Metric[13][i]):(Metric[3][i] + Branch_Metric[2][i]);
Path_Metric[1][i+1] = ((Metric[2][i] + Branch_Metric[13][i]) > (Metric[3][i] + Branch_Metric[2][i]))? 2:3;
Metric[2][i+1] = ((Metric[4][i] + Branch_Metric[10][i]) > (Metric[5][i] + Branch_Metric[5][i]))? (Metric[4][i] + Branch_Metric[10][i]):(Metric[5][i] + Branch_Metric[5][i]);
Path_Metric[2][i+1] = ((Metric[4][i] + Branch_Metric[10][i]) > (Metric[5][i] + Branch_Metric[5][i]))? 4:5;
Metric[3][i+1] = ((Metric[6][i] + Branch_Metric[7][i]) > (Metric[7][i] + Branch_Metric[8][i]))? (Metric[6][i] + Branch_Metric[7][i]):(Metric[7][i] + Branch_Metric[8][i]);
Path_Metric[3][i+1] = ((Metric[6][i] + Branch_Metric[7][i]) > (Metric[7][i] + Branch_Metric[8][i]))? 6:7;
Metric[4][i+1] = ((Metric[8][i] + Branch_Metric[12][i]) > (Metric[9][i] + Branch_Metric[3][i]))? (Metric[8][i] + Branch_Metric[12][i]):(Metric[9][i] + Branch_Metric[3][i]);
Path_Metric[4][i+1] = ((Metric[8][i] + Branch_Metric[12][i]) > (Metric[9][i] + Branch_Metric[3][i]))? 8:9;
Metric[5][i+1] = ((Metric[10][i] + Branch_Metric[1][i]) > (Metric[11][i] + Branch_Metric[14][i]))? (Metric[10][i] + Branch_Metric[1][i]):(Metric[11][i] + Branch_Metric[14][i]);
Path_Metric[5][i+1] = ((Metric[10][i] + Branch_Metric[1][i]) > (Metric[11][i] + Branch_Metric[14][i]))? 10:11;
Metric[6][i+1] = ((Metric[12][i] + Branch_Metric[6][i]) > (Metric[13][i] + Branch_Metric[9][i]))? (Metric[12][i] + Branch_Metric[6][i]):(Metric[13][i] + Branch_Metric[9][i]);
Path_Metric[6][i+1] = ((Metric[12][i] + Branch_Metric[6][i]) > (Metric[13][i] + Branch_Metric[9][i]))? 12:13;
Metric[7][i+1] = ((Metric[14][i] + Branch_Metric[11][i]) > (Metric[15][i] + Branch_Metric[4][i]))? (Metric[14][i] + Branch_Metric[11][i]):(Metric[15][i] + Branch_Metric[4][i]);
Path_Metric[7][i+1] = ((Metric[14][i] + Branch_Metric[11][i]) > (Metric[15][i] + Branch_Metric[4][i]))? 14:15;
Metric[8][i+1] = ((Metric[0][i] + Branch_Metric[15][i]) > (Metric[1][i] + Branch_Metric[0][i]))? (Metric[0][i] + Branch_Metric[15][i]):(Metric[1][i] + Branch_Metric[0][i]);
Path_Metric[8][i+1] = ((Metric[0][i] + Branch_Metric[15][i]) > (Metric[1][i] + Branch_Metric[0][i]))? 0:1;
Metric[9][i+1] = ((Metric[2][i] + Branch_Metric[2][i]) > (Metric[3][i] + Branch_Metric[13][i]))? (Metric[2][i] + Branch_Metric[2][i]):(Metric[3][i] + Branch_Metric[13][i]);
Path_Metric[9][i+1] = ((Metric[2][i] + Branch_Metric[2][i]) > (Metric[3][i] + Branch_Metric[13][i]))? 2:3;
Metric[10][i+1] = ((Metric[4][i] + Branch_Metric[5][i]) > (Metric[5][i] + Branch_Metric[10][i]))? (Metric[4][i] + Branch_Metric[5][i]):(Metric[5][i] + Branch_Metric[10][i]);
Path_Metric[10][i+1] = ((Metric[4][i] + Branch_Metric[5][i]) > (Metric[5][i] + Branch_Metric[10][i]))? 4:5;
Metric[11][i+1] = ((Metric[6][i] + Branch_Metric[8][i]) > (Metric[7][i] + Branch_Metric[7][i]))? (Metric[6][i] + Branch_Metric[8][i]):(Metric[7][i] + Branch_Metric[7][i]);
Path_Metric[11][i+1] = ((Metric[6][i] + Branch_Metric[8][i]) > (Metric[7][i] + Branch_Metric[7][i]))? 6:7;
Metric[12][i+1] = ((Metric[8][i] + Branch_Metric[3][i]) > (Metric[9][i] + Branch_Metric[12][i]))? (Metric[8][i] + Branch_Metric[3][i]):(Metric[9][i] + Branch_Metric[12][i]);
Path_Metric[12][i+1] = ((Metric[8][i] + Branch_Metric[3][i]) > (Metric[9][i] + Branch_Metric[12][i]))? 8:9;
Metric[13][i+1] = ((Metric[10][i] + Branch_Metric[14][i]) > (Metric[11][i] + Branch_Metric[1][i]))? (Metric[10][i] + Branch_Metric[14][i]):(Metric[11][i] + Branch_Metric[1][i]);
Path_Metric[13][i+1] = ((Metric[10][i] + Branch_Metric[14][i]) > (Metric[11][i] + Branch_Metric[1][i]))? 10:11;
Metric[14][i+1] = ((Metric[12][i] + Branch_Metric[9][i]) > (Metric[13][i] + Branch_Metric[6][i]))? (Metric[12][i] + Branch_Metric[9][i]):(Metric[13][i] + Branch_Metric[6][i]);
Path_Metric[14][i+1] = ((Metric[12][i] + Branch_Metric[9][i]) > (Metric[13][i] + Branch_Metric[6][i]))? 12:13;
Metric[15][i+1] = ((Metric[14][i] + Branch_Metric[4][i]) > (Metric[15][i] + Branch_Metric[11][i]))? (Metric[14][i] + Branch_Metric[4][i]):(Metric[15][i] + Branch_Metric[11][i]);
Path_Metric[15][i+1] = ((Metric[14][i] + Branch_Metric[4][i]) > (Metric[15][i] + Branch_Metric[11][i]))? 14:15;
i=i+1;
}
//_______________________________________________Decoding_________________________________
int max = Metric[0][i];
int index = 0;
int ii;
// find last MAX value in trellis graph
for (ii = 0; ii < 16; ii++)
{
if (max < Metric[ii][i])
{
max = Metric[ii][i];
index = ii;
}
}
// Trace back and decode bits function
unsigned int x_axis =i;
unsigned int y_axis= index;
while (x_axis !=0)
{
if ((y_axis ==0) || (y_axis ==1) || (y_axis ==2) || (y_axis ==3) || (y_axis ==4) || (y_axis ==5) || (y_axis ==6) || (y_axis ==7))
{
y_axis = Path_Metric[y_axis][x_axis];
Output_Data[x_axis] =0;
x_axis=x_axis-1;
}
else if ((y_axis ==8) || (y_axis ==9) || (y_axis ==10) || (y_axis ==11) || (y_axis ==12) || (y_axis ==13) || (y_axis ==14) || (y_axis ==15))
{
y_axis = Path_Metric[y_axis][x_axis];
Output_Data[x_axis] =1;
x_axis=x_axis-1;
}
} // End of WHILE loop
}