OFDMA 1024 subcarrier generation and gain of each subcarrier

[elegant]

Hi,
i am literally confused as i need to generate 1024 subcarriers for DL frame. i have to then select the 24 subcarriers using PUSC for a one symbol.I don't have any data bits but i do have data rate that is to be sent.

% data for user 1
data_to_be_sent=1000bits/frame

% data after 64QAM3/4 coding and modulation scheme
data_to_be _sent_after AMC=1000*6*(3/4)

%24 data subcarriers
n=randperm(1024)%0 is not considered+ pilot subcarriers are not considered
s(1-24)=cos(2*pi*fc*n)
randomly selected subcarriers=[1, 45,78,.....]

i want to compute the channel gain of each of the selected subcarrier.

1) do i need IFFT of s which i think is only done when i want data bits to be modulated(64QAM) and mapped on subcarrier

2)how do i get channel gain after passing each of s(subcarrier)
through Rayleigh fading channel using matlab Rayleighchannel command

thanks in advance...

 

[WiMAX-]

Dear elegant
mostly I face the same problem please if you find solution tagged me, thank you.