Walsh Hadamard Code – Matlab Simulation

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The following is a function to generate a Walsh Hadamard Matrix of given codeword size. The codeword size has to be a power of 2.

function [H]=generateHadamardMatrix(codeSize)

%[H]=generateHadamardMatrix(codeSize);
% Function to generate Walsh-Hadamard Matrix where "codeSize" is the code
% length of walsh code. The first matrix gives us two codes; 00, 01. The second
% matrix gives: 0000, 0101, 0011, 0110 and so on
% Author: Mathuranathan for https://www.gaussianwaves.com
% License: Creative Commons: Attribution-NonCommercial-ShareAlike 3.0
% Unported

%codeSize=64; %For testing only
N=2;
H=[0 0 ; 0 1];
if bitand(codeSize,codeSize-1)==0
while(N~=codeSize)
       N=N*2;
       H=repmat(H,[2,2]);
       [m,n]=size(H); 

      %Invert the matrix located at the bottom right hand corner
      for i=m/2+1:m,
          for j=n/2+1:n,
                H(i,j)=~H(i,j);
         end
     end
end
else
disp('INVALID CODE SIZE:The code size must be a power of 2');
end

Example:

To Generate Walsh Codes used in IS-95 (which utilizes 64 Walsh codes of size 64 bits each, use : [H]=generateHadamardMatrix(64). This will generate 64 Walsh Codes of length 64-bits (for each code).

Test Program:

Click Here to download
Also given below is a program to test the cross-correlation and auto-correlation of Walsh code. A set of 8-Walsh codes are used for this purpose.

% Matlab Program to test Walsh Hadamard Codes and to test their orthogonality
% Plots cross-correlation and auto correlation of Walsh Hadamard Codes
% Author: Mathuranathan Viswanathan for https://www.gaussianwaves.com
% License: Creative Commons: Attribution-NonCommercial-ShareAlike 3.0
% Unported

codeSize=8;
[H]=generateHadamardMatrix(codeSize);

%-----------------------------------------------------------
%Cross-Correlation of Walsh Code 1 with rest of Walsh Codes
h = zeros(1, codeSize-1); %For dynamic Legends
s = cell(1, codeSize-1); %For dynamic Legends
for rows=2:codeSize
[crossCorrelation,lags]=crossCorr(H(1,:),H(rows,:));
h(rows-1)=plot(lags,crossCorrelation);
s{rows-1} = sprintf('Walsh Code Sequence #-%d', rows);
hold all;
end

%Dynamic Legends
% Select the plots to include in the legend
index = 1:codeSize-1;

% Create legend for the selected plots
legend(h(index),s{index});
title('Cross Correlation of Walsh Code 1 with the rest of the Walsh Codes');
ylabel('Cross Correlation');
xlabel('Lags');

%-----------------------------------------------------------
%AutoCorrelation of Walsh Code - 1
autoCorr2(H(2,:),8,2,1);

Simulation Results

See also:

[1] Codes used in CDMA
[2] Generation of Gold Codes and their cross-correlation
[3] Preferred Pairs m-sequences generation for Gold Codes
[4] Maximum Length Sequences ( m-sequences)
[5] Introduction to Spread Spectrum

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