GNURadio OFDM multiple data in subcarriers.

Hi all,

I was trying to send contents of a file using a single subcarrier in OFDM. As Marcus pointed out, it is a complex process and i found out that using a single data carrier for the main data apart from the carriers for the header and sync words, the channel estimation takes forever. The data is never decoded.

What I want to do is use different subcarriers of the OFDM transmitter to send different file contents. Say use subcarrier 3, 4 to send contents of file 1 and subcarriers 7, 8 to send contents of file 2. I want to do it simultaneously. I am using USRP B200 on both. I tried using 2 flowgraphs, one for each file, in the same grc file for doing it. The transmitter seems to send the required data. I tried decoding it with the loopback flowgraph. The output was redirected to the terminal. The contents were being printed properly.  But whenever I use the USRP, the receiver side just stops working. The receiver side also has 2 flowgraphs running with the corresponding values of the subcarriers.

For ofdm transmitter 1, the parameter values are:

Occupied carriers- ((-2, -1, 2, 1 3, 4),)

Pilot carriers- ((-21, -11, 11, 21),)

Pilot symbols- ((-1, 1, -1, 1),)

For ofdm transmitter 2, the parameter values are:

Occupied carriers- ((-4, -3, -5, -6, 6, 7),)

Pilot carriers- ((-26, -25, 26, 25),)

Pilot symbols- ((-1, 1, -1, 1),)

I want to do it using a single flowgraph. What would be the right way to proceed with this?