Modeling OFDM multipath channel in Matlab

Dear all,

I have a basic question regarding modeling of a multipath channel for OFDM
in Matlab and would appreciate your help.

My intention is to simulate an 802.11a transmission which uses OFDM. From
the 802.11a standard I know that:
-Number of Subcarriers, Nsc = 64
-Sampling Rate at the receiver, fs = 20e6 samples/sec
-BW = 20Mhz
-Carrier Frequency, fc = 5.25 Ghz

Now consider that I have the following channel impulse response:
-taps_delay = [0 10ns 20ns 30ns]
-taps_amp = [0.5 0.2 0.01 0.002]

What I want to do is to find out the channel frequency response in each
802.11a OFDM subcarrier. Could you please tell me if the following steps
are correct or correct them otherwise ?

1- Use the baseband representation of the channel impulse response by
defining the following vector:

h_bb = taps_amp .* exp(-j*2*pi*fc*taps_delay);

2- To obtain the frequency response of the channel make the FFT of the
baseband representation of the channel impulse response, with at least as
many points as OFDM subcarriers 802.11a has:

H_f = fft(h_bb, Nsc);

Is each point of H_f the frequency response that each OFDM subcarrier will
see ?

3- Now if I want to represent graphically the frequency response of the
channel I would do:

f = fs*(0:Nsc-1)/Nsc; % Frequency in Hz
plot(f, H_f .* conj(H_f));

Where my question here is whether to pass from the discrete frequency
obtained through the FFT to Hz I have to use the sampling frequency in the
receiver, fs.


Thanks for your help.

Daniel