generating pilot sub-carriers in matlab I wanted to simulate OFDM system in MATLAB. I'm using Fixed WiMAX OFDM parameters in my simulation, where the number of data sub-carriers are 192, number of Pilot sub-carriers are 8, number Null sub-carriers are 56.
Null tones can be obtained in MATLAB by generating zero matrix with the required rows and columns. 

% Null subcarrier:
msg(1,1:100)=0;


similarly, for data subcarriers, digitally modulated data is sent. 

% Data subcarrier:
msg(2,1:100)= 1*sign(randn(1,100)) + i*sign(randn(1,100));


my question is, what type of data could I send for Pilot tones?? all books and literature I have read says that: Pilot tones are just known data. 
What type of Known data are the Pilot tones? What kind of data should I send in my specific problem? Please, clarify.
In your case, each OFDM symbol contains 256 sub-carriers. Store the pilot values for a OFDM symbol at time instant $n$ in an $8 \times 1$ array say V. Also, you have the positions of the pilot carriers stored in a array say, P. Let the OF(:,n) represent the $256 \times 1$ OFDM symbol at time n. 

Then you can assign the pilot values V to the corresponding pilot positions P in the OFDM symbol at time n as

OF(P,n)=V


in MATLAB. I hope this helps you a bit.