channel1.m

function varargout = channel1(sig,SNRdB,NR)

%MIMO-OFDM Wireless Communications with MATLAB¢ç   Yong Soo Cho, Jaekwon Kim, Won Young Yang and Chung G. Kang
%2010 John Wiley & Sons (Asia) Pte Ltd

ch_conf=[2 NR];
[N_frame,space_dim,N_packets]=size(sig);
spowr = sum(abs(sig(:,1,1)))/N_frame;
sigma = sqrt(0.5*spowr*(10^(-SNRdB/10)));  sq2 = sqrt(2);
ch_coefs=(randn(ch_conf(1),ch_conf(2),N_packets) +...
           j*randn(ch_conf(1),ch_conf(2),N_packets))/sq2 ;
ch_noise= sigma*(randn(N_frame,ch_conf(2),N_packets) +...
           j*randn(N_frame,ch_conf(2),N_packets));  
for k = 1:N_packets 
   sig_add(:,:,k) = sig(:,:,k)*ch_coefs(:,:,k);
end
sig_corr = (sig_add + ch_noise); 
varargout = {sig_corr,ch_coefs};