alamouti.m

Hybrid DS-FH communication systems

%Simulation parameters for the verson without GUI
N=100; %total number of symbol pairs to be transmitted (should be at least 10 times more than expected 1/min(BER))
M=2;   %PSK order (must be a power of 2): 2, 4, 8 etc'
SNR=0:10; %SNR in dB, average received power at one Rx element over the average noise power at that element
Tx=2; %number of Tx elements, must be 2
Rx=1; %number of Rx elements

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%Resets the generators to their initial state
randn('state',0); %Remove it if you want a random start of the randn generator
rand('state', 0); %Remove it if you want a random start of the rand generator

%Monte-Carlo
for k=1:length(SNR)
    %Toss pairs of uniformly distributed MPSK symbols with power 1/2
    A=floor(M*rand(2,N)); %transmitted alphabet
    st=exp(j*2*pi/M*A)/sqrt(2); %transmitted symbols
    
    %Simulate equivalent matrix of impulse noise
    %Noise power caculation
    snr=10^(SNR(k)/10); %just translate SNR from dB to times
    
    sig1=0.5/snr; %the sigma square of the noise
    
    Ns=sqrt(sig1)*(randn(2*Rx,N)+j*randn(2*Rx,N)); %noise matrix 
    
    %Transceiver
    for n=1:N
        %Toss the channel complex coefficients
        H=[]; %equivalent channel matrix initialization
        for r=1:Rx
            
            %h=(randn(1,2)+j*randn(1,2))/sqrt(2); %Rayleigh channel
              h=ones(1,2); %flat channel

            %Equivalent channel matrix:
            %h(1) - from first Tx to current Rx; h(2) - from second Tx to current Rx
            H=[H; h(1) h(2); h(2)' -h(1)'];
        end %m
    
        sr(:,n)=H'*H*st(:,n)+H'*Ns(:,n); %received symbols
    end %n
    
    %ML detection
    ang=angle(sr); %received angles
    B=mod(round(ang/(2*pi/M)),M); %received alphabet
   
    %BER estimation (for the Gray code constellations)
    BER(:,k)=sum(sum(xor(A-B,0)))/2/N/log2(M);
    
end %k (SNR)
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%Create plot

semilogy(SNR, BER, 'k-v');
xlabel('SNR, [dB]');
ylabel('BER');

grid on