[Discuss-gnuradio] few queries on OFDM implementation

[Sheshanandan KN]

Hi all,
I am yet to figure out the answers to the following basic questions
which was posted sometime back and somehow got missed out. It will
help in proper understanding of 'ofdm' implemented on gnuradio and
inturn will aid me to take it to the next level of my experimentation.
Please help me get answers to these questions.

Tom,
if you can give some inputs, it will be great.

Here we specify the center frequency at which the ofdm signal is going
to be transmitted.

1) Is this the center frequency of the sub-carrier of a particular
channel? If so, what is the bandwidth used?
2) If not, how the sub-carrier is differentiated from the channel? How
many sub-carriers are supported?
3) The modulation parameter is the modulation technique defined for a
particular sub-carrier, right? If so, can we also define a different
modulation technique to be used at runtime once we switch to a
different frequency?
4) Why the interpolation/decimation values need to be specified for
this experiment?

5) My present setup consists of: 2 USRPs connected to 2 different PCs.
The PCs are connected to a LAN. I do OFDM transmission at a frequency
which is sensed to be free. I want to send this information to the
OFDM receiver so that it also shifts its frequency of reception. I am
not getting how this can be achieved in gnuradio?  Can we do this by
extracting this information through the ethernet connection between
the 2 PCs?

Shesh