walsh.cpp

Generate orthogonal Walsh codes, which can be used in wireless communications such as CDMA system.

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include <iostream.h>

#define  SF		4
int      DSpreadCode[SF][SF];


void  GENERATE_WALSH_SPREADCODE(void)      		/* Generate Walsh spreading sequences */
{
	/* Purpose: Generate Walsh spreading sequences*/
	/* Output parameters: DSpreadCode[SpreadTotle][SpreadTotle]*/	
	int k, x, y;
	int k_length;
	
	DSpreadCode[0][0] = 1;
	
	// The define of Ik should according to the length of SpreadTotle
	// It should statisfy that: pow(2, Ik) = SpreadTotle
	k_length = (int)(log10(SF+0.5)/log10(2));
		
	for(k = 1; k <= k_length; k++)
	{
		for(x = 0; x < (int)pow(2.0, k); x++)
		{			
			for(y = 0; y < (int)pow(2.0, k); y++)
			{
				if (x < (int)(pow(2.0, k-1)))
				{
					if(y < (int)(pow(2.0, k-1)))	{DSpreadCode[x][y] = DSpreadCode[x][y];	}
					else			{DSpreadCode[x][y] = DSpreadCode[x][y-(int)(pow(2.0, k-1))];}
				}				
				else
				{
					if(y < (int)(pow(2.0, k-1)))	{DSpreadCode[x][y] = DSpreadCode[x-(int)(pow(2.0, k-1))][y];}
					else			{DSpreadCode[x][y] = (-1) * DSpreadCode[x-(int)(pow(2.0, k-1))][y - (int)(pow(2.0, k-1))];}
				}//if			
			}//y
		}//x
	}//k
}

void main()
{
	int i, j;
	GENERATE_WALSH_SPREADCODE();
	for(i = 0; i < SF; i++) {
		for(j = 0; j < SF; j++) {
			printf("%d\t", DSpreadCode[i][j]);
		}
		printf("\n");
	}
}