Transceiver--OFDM (digital) modulation

Hi,

I am trying to implement a digital transmission, using BPSK, QPSK, QAM
and later to use OFDM.

  1. I tried using the defined blocks source signal->packet
    encoder->digital mod-> digital demod->sink
    It worked perfectly.
    2.Sending the modulated signal through UHD Sink-> UHD Source… nothing
    happened. I started reading about frequency offset, time
    synchronization…but i didn’t find any solution. So if someone knows
    more about this problem please reply.
    3.Testing using python. Benchmark_tx/rx worked well, but having problems
    with ofdm_mod_demod.py which when i run it gives this error :

./ofdm_mod_demod_test.py
Traceback (most recent call last):
File “./ofdm_mod_demod_test.py”, line 178, in
main()
File “./ofdm_mod_demod_test.py”, line 148, in main
tb = my_top_block(rx_callback, options)
File “./ofdm_mod_demod_test.py”, line 44, in init
self.ofdm_mapper = gr.ofdm_bpsk_mapper(4, options.occupied_tones,
options.fft_length, ks1, ks2)
AttributeError: ‘module’ object has no attribute ‘ofdm_bpsk_mapper’

Does anybody know how to solve it?
And one more question, is it possible to make a python file to allow
transmitting and receiving on the same UHD USRP(N210)?