implementing a frequency selective fading channel

hi ya , the followin is th code for a BER simulation of a modulated qpsk signal over a flat fading channel and my question is how can implement a frequency selective fading on it ( 2-ray ) from what i read it says i have to add a delay tau into the impulse reponse function h but am not exactly sure how to do that, any helo wud be appreciated guys thanks


N_loop = 100;
N_sym = 10^4;
N_bit=2*N_sym;
awgn_sigma = sqrt(0.5);
Eb_dB=5:1:9
Eb = 10.^(Eb_dB/10);
sqrt_Es = sqrt(2*Eb);
BER = zeros(1,length(Eb));
normalized = 1/sqrt(2);

for n=1:N_loop;
D = floor(2*rand(1,N_sym))+j*floor(2*rand(1,N_sym));
Tx_data = normalized * (2*D-(1+j));
h=randn(1,1)+j*randn(1,1);
Noise=awgn_sigma*(randn(N_sym,length(Eb_dB))+j*randn(N_sym,length(Eb_dB)));
Rx_data = (h*transpose(Tx_data)*sqrt_Es) + Noise;
Recov_data1 =Rx_data/h;
Recov_data2 = 0.5*(1+j+sign(real(Recov_data1))+j * sign(imag(Recov_data1)));
BER = BER+sum((abs(Recov_data2-transpose(D)*ones(1,length(Eb_dB)))).^2)/N_bit;
end;
BER = BER/N_loop

semilogy(Eb_dB,BER,'*-');
xlabel('Eb/N0 (dB)');
ylabel('BER');