x = [0.7+0.7i; 0.70-0.7i; 0.7i+0.7i; -0.7+0.7i];    %generate signal x
h = (randn(Nr,Nt) + 1j.*randn(Nr,Nt))/sqrt(2);      %Generate 4x4 channel
code = hadamard(4)                                  %generate walsh code
x_s = kron(x,cod(:,1))                              %spread the signal x with one walsh code
r = reshape(h*reshape(x_s,4,[])',[],1);              % the received signal with AWGN