Could you please tell me how I can remove the effect of fading in an
BPSK OFDM receiver?
 
    My channel is a static flat fading:
 
    gnoise = (noise_var) * sqrt(1/2) * (randn(1,symbol_size) +
j*randn(1,symbol_size))
    a = randn(1,symbol_size) + j*randn(1,symbol_size) 
    r = a.*ofdm_symbol + gnoise

    at the receiver I have tried the following techniques to remove the 
    effect of channel:

    y = fft(ofdm_sym)./fft(a)

    and also in another attempt I tried:
 
    temp = r .* conj(a)
    y = fft(temp)

    unfortunately none of them help me to get an error rate near the
theoretical curve for BPSK OFDM flat fading.

You need to add a BFO and run SSB.