Queries on ofdm implementation


Hi all,
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. I have a few questions on this:

  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.