OFDM mod-demod

hi
I was doing OFDM modulation demodulation in following way
file source —> OFDM Mod —> Virtual Source
Virtual Sink —> OFDM demod —> File sink
File source out is given in byte format. This system give output for
bpsk, qpsk and 8psk modulation. and no output for QAM schemes. What
changes are to be made to do QAM modulations also.
Regards
Sreena