fwht.m

该系统主要使用matlab实现了stbc2*1系统的发送和接收

%----------------------------------------------------------------------
%	y=fwht(x)
%	----------
%	- fast Hadamard-ordered Walsh-Hadamard Transform (fwht)
%	- input:
%		x --- a real or complex matrix with m by n elements
%	- output:
%		y --- fwht coeficients of x column by column
%-------------------------------------------------------------------------

%----------------------------------------------------------------
%$	fast Hadamard-ordered Walsh-Hadamard Transform (fwht)	
%   Dependencies:
%	none	
%   Compatability:
%	Matlab Ver 3.5g, Ver 4.1a
%   Notes:
%   References: N. Ahmed and K.R. Rao:"Orthogonal transforms for
%		digital signal processing",(springer-verlag, New
%		York, 1975) 
%
%-----------------------------------------------------------------

function y=fwht(x)

	[m,n]=size(x);
	k=ceil(log2(m));
	K=2^k;

	z=[x;zeros(K-m,n)];
	up=zeros(1,K/2);
	down=up;

	for l=1:k

		GN=2^(l-1);
		G=2^(k-l+1);
		up0=1:G/2;
		down0=up0+G/2;

		d=(0:GN-1)*G;
		up=reshape((ones(GN,1)*up0)'+ones(G/2,1)*d,1,K/2);
		down=reshape((ones(GN,1)*down0)'+ones(G/2,1)*d,1,K/2);
		reorder=reshape([up;down]',1,K);
		z(reorder,:) =[z(up,:)+z(down,:);z(up,:)-z(down,:)];
end

	y=z/K;

return