Alamouti_2x1_ant_selection.m

% Alamouti_2x1_ant_selection.m

%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

clear all; clf
%%%%%% Parameter Setting %%%%%%%%%
N_packet=100;  N_frame=100;  
mod_order=2;  M=2^mod_order;
mod_obj=modem.qammod('M',M,'SymbolOrder','Gray','InputType','bit');
demod_obj = modem.qamdemod(mod_obj);
% MIMO Parameters
T_TX=4;  NT=2; NR=1; 
n_bits=NT *mod_order*N_frame;  N_tbits=n_bits*N_packet;
fprintf('====================================================\n');
fprintf('  Ant_selection transmission');
fprintf('\n  %d x %d MIMO\n  %d QAM', NT ,NR,M);
fprintf('\n  Simulation bits : %d',N_tbits);
fprintf('\n====================================================\n');
SNRdBs = [0:2:20];  sq2=sqrt(2);
for i_SNR=1:length(SNRdBs)
   SNRdB= SNRdBs(i_SNR);  
   noise_var = NT *0.5*10^(-SNRdB/10); sigma = sqrt(noise_var);
   rand('seed',1); randn('seed',1);  N_ebits = 0;
   %%%%%%%%%%%%% Transmitter %%%%%%%%%%%%%%%%%%
   for i_packet=1:N_packet
      msg_bit = randint(n_bits,1); % Bit generation
      s = modulate(mod_obj,msg_bit);
      Scale = modnorm(s,'avpow',1); % Normalization factor
      S=reshape(Scale*s,NT ,1,N_frame); 
      Tx_symbol=[S(1,1,:)  -conj(S(2,1,:)); S(2,1,:)   conj(S(1,1,:))];    
      %%%%%%%%%%%%% Channel and Noise %%%%%%%%%%%%%
      H = (randn(NR,T_TX)+j*randn(NR,T_TX))/sq2;
      for TX_index=1:T_TX
         ch(TX_index)=norm(H(:,TX_index),'fro'); 
      end
      [val,Index] = sort(ch,'descend');
      Hs = H(:,Index([1 2])); 
      norm_H2=norm(Hs,'fro')^2; % H selected and its norm2
      for i=1:N_frame
         Rx(:,:,i) = Hs*Tx_symbol(:,:,i) + ... 
                      sigma*(randn(NR,2)+j*randn(NR,2));
      end
      %%%%%%%%%%%%% Receiver %%%%%%%%%%%%%%%%%%
      for i=1:N_frame
         y(1,i) = (Hs(1)'*Rx(:,1,i)+Hs(2)*Rx(:,2,i)')/norm_H2;
         y(2,i) = (Hs(2)'*Rx(:,1,i)-Hs(1)*Rx(:,2,i)')/norm_H2;
      end     
      S_hat = reshape(y/Scale,NT *N_frame,1);
      msg_hat = demodulate(demod_obj,S_hat);
      N_ebits = N_ebits + sum(msg_hat~=msg_bit);
    end
    BER(i_SNR) = N_ebits/N_tbits;
end
semilogy(SNRdBs,BER,'-k^', 'LineWidth',2); hold on; grid on;
xlabel('SNR[dB]'), ylabel('BER');
legend('Ant-selection transmission')