ofdm_fading.m

OFDM- equalization for fading channels

clear;
L=256;%OFDM symbol length
FRAME=5000;%The number of OFDM symbols
R=1;
Eb_No_dB=30;
Eb_No=10^(Eb_No_dB/10);
SNR=Eb_No*R;
std_dev=sqrt(1/SNR/2);%define SNR

%h=[0.688 .46 .46 .227 .227];%Channel impulse response

BE=0;
for frame=1:1:FRAME,
    h=[0.81*(randn(1,1)+j*randn(1,1))/sqrt(2),0.5*(randn(1,1)+j*randn(1,1))/sqrt(2),0.31*(randn(1,1)+j*randn(1,1))/sqrt(2)];%Channel impulse response
    H=zeros(1,L);
    for l=1:1:L,
        for p=1:1:3,
            H(l)=H(l)+h(p)*exp(-j*2*pi*(l-1)*(p-1)/L);
        end
    end
    X=2*randint(1,L)-1;
    x=sqrt(L)*ifft(X);
    %x=transpose(F'*X');%IDFT
    
    for m=1:1:3,
        CP(m)=x(L-5+m);
        %CP(m)=0;
    end
    x=[CP x];%add CP

    y=conv(h,x);%channel
    y=y+(randn(1,length(y)))*std_dev+j*(randn(1,length(y)))*std_dev;
    temp=zeros(1,L);
    for m=1:1:L,
        temp(m)=y(m+3);    
    end
    y=temp;%Truncate the OFDM symbol
    
    Y=fft(y)/sqrt(L);
    %Y=Y./H;%Frequency domain ZF equalization
    Y=Y.*conj(H)./(H.*conj(H)+2*std_dev*std_dev);%Frequency domain MMSE equalization
    BE=BE+sum(abs(sign(real(Y))-X))/2;
end
BER=BE/L/FRAME