A few queries related to ofdm implementation


Hi,I am using the trunk repository with revision no. 11025. I am
presently experimenting on ofdm. The given code is working fine on the
USRP setup. 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) Is it possible to switch to a
different frequency at runtime? 4) 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?5) The preamble defined
for the packets - are they standardized? I mean to say, any ofdm packet
will be having the same preamble?6) Why the interpolation/decimation
values need to be specified for this experiment alone? This is not the
case for other examples given in ‘gnuradio-examples’ folder.Please help
me figure out the answers for these. It will help in proper
understanding of ofdm implemented on gnuradio.Shesh