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% Walsh_index: Gives the Walsh indices of an alternating code set

% GUISDAP v.1.60 96-05-27 Copyright Asko Huuskonen and Markku Lehtinen

% Function to give the Walsh indices of an alternating code set

% Nbits : number of bits in the code

% index : indices specifying the alternating code set in decimal base

% NC    : number of codes in the complete set

% function [index,NC]=Walsh_index(Nbits);

  function [index,NC]=Walsh_index(Nbits);

		

		

% the original Walsh index definitions are in octal base

% because he original references give the indices so

if Nbits>32 & Nbits<=64

  octal=[0 1 2 4 10 20 40 100 137 140 36 75 172 53 127 ...

         161 74 171 55 133 151 14 31 62 144 27 57 136 ...

         143 30 61 142 33 67 156 3 7 16 34 70 160 77 ...

         177 41 103 131 154 6 15 32 64 150 17 37 76 ...

         174 47 117 101 134 146 22 45 112]; NC=128;

elseif Nbits>16 & Nbits<=32

	 octal=[0 1 2 4 10 20 40 30 61 72 55 3 7 16 34 70 50 11 23 ...

		       46 24 51 12 25 52 14 31 62 74 41 33 67]; NC=64;

elseif Nbits>8 & Nbits<=16

  octal=[0 1 2 4 10 20 36 3 7 16 34 6 15 32 12 25]; NC=32;

elseif Nbits>4 & Nbits<=8

  octal=[0 1 2 4 10 3 7 16]; NC=16;  

elseif Nbits>2 & Nbits<=4

  octal=[0 1 2 4]; NC=8;  

else

  fprintf(' No Walsh index set available for %.0f bits\n',Nbits)

		error(' ')

end



% Change from octal to decimal numbers

index=zeros(size(octal));

mult=1;

while any(octal>0)

  index=index+rem(octal,10)*mult;

  mult=mult*8;

  octal=floor(octal/10);

end



index=index(1:Nbits);