# OFDM Transceiver to send/receive messages

**URL:** <https://www.ruby-forum.com/t/ofdm-transceiver-to-send-receive-messages/256895>\
**Category:** GNU Radio\
**Created:** [February 29, 2020, 4:27pm UTC](https://www.ruby-forum.com/t/ofdm-transceiver-to-send-receive-messages/256895 "2020-02-29T16:27:57Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![tuyo408](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/d07c76/32.png) [@tuyo408](https://www.ruby-forum.com/u/tuyo408)\
**Post date:** [February 29, 2020, 4:27pm UTC](https://www.ruby-forum.com/t/ofdm-transceiver-to-send-receive-messages/256895/1 "2020-02-29T16:27:57Z")

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Hello,

I am trying to implement an OFDM transceiver using 2 USRP B200 in order to use each one of them as a chat client using message passing, in order to send and receive messages on both.  
So far I have been able to make the communication working unidirectionally, so I can send a message and receive it on the other side.

Then I tried to merge my TX and RX flowgraphs into one having both to build a transceiver. Unfortunately I did not succeed to have a working flowgraph so far.  
I assigned the TX/RX antenna to the USRP Source and RX2 to the USRP Sink, different frequencies for uplink and downlink…  
When I test my flowgraph I can actually see that something is sent on the TX LED and the RX antenna is continuously receiving on the RX side.  
I think I would have to connect my RX and TX flowgraphs in some way so that I can be able to transmit and receive at the same time, which doesn’t look to be the case.

Someone would have a working example of an OFDM transceiver so that I see what I miss ?

Below are my TX+RX flowgraph (the separate TX and RX flowgraphs are working autonomously) and the python file I modified in order to integrate the chat aspect at the beginning and end of my flowgraphs.

The GRC:  
[https://github.com/abeyaert/OFDM\_Message\_Paging/blob/master/tx\_rx\_ofdm\_b200.grc](https://github.com/abeyaert/OFDM_Message_Paging/blob/master/tx_rx_ofdm_b200.grc)  
Python with chat features :  
[https://github.com/abeyaert/OFDM\_Message\_Paging/blob/master/tx\_rx\_ofdm\_b200.py](https://github.com/abeyaert/OFDM_Message_Paging/blob/master/tx_rx_ofdm_b200.py)

Any suggestion on them would be appreciated.

Anthony