This might be relevant to the “ofdm occupied tones concept”
thread on this list.
I have uploaded some code on github that implements an OFDM tx/rx
with arbitrary modulation schemes per carrier.
The user specifies a list of constellations
(say, zeros, or pilots or QPSK or 16QAM) and then the index of the
constellation per carrier. This way you can place zeros and pilots
anywhere you want and also arbitrary modulations per carrier.
You can download the code from
http://anastas.github.com/gnuradio-anastas/
and check the grc examples provided in gr-howto-write-a-block/apps
howto_ofdm_tx.grc
howto_ofdm_tx_Q2.grc
There is a working frequency/phase correction block as well, but this is
still WIP and the timing algorithms are not there yet.
Achilleas