I've been playing around with the OFDM TX/RX for a while, and I thought it would be interesting to send over the air custom messages and display the waveform at the receiver. For that purpose, I took the chat sanitizer and receiver block that I came across from [1]. The OFDM header modulation resulted helpful for synchronization and tag generation at the receiver, which is is continuously running for burst samples. However, with the sanitizer in the flowgraph, the TX becomes asynchronous, sending data only when an "enter" is hit in the msg text entry box.
The flowgraph is basically the same OFDM example found in gnuradio/gr-digital/examples/ofdm, but with the chat sanitizer and async crc as input from the Tx, and a chat receiver (with respective crc check) at the end of the demodulator at the Rx. I'm using a sampling rate of 500k and as USRP the ettus x310 units
With this configuration, I am able to receive only one message, corresponding to the first sent from the Tx, but after this one I haven't been able to receive more. The following messages seem to be lost in the air, but I can see that there is some transmission being done as I see the OFDM spectrum in a frequency sink at the receiver. My first thought is that it was a synchronization problem at the receiver, but then I noticed that If I restart only the Tx several times after sending one message each time, the receiver can catch them, but never more than one per Tx run, so the header is being received and analyzed. Now I'm thinking that the Tx is sending stuff that do not correspond to the messages that I'm sending. However I connected a loop back with a, lets say, virtual OFDM demodulator at the Tx, and in there I can see my messages being propagated.
Now I'm running out of ideas of why my messages are not coming through. Any ideas on how I can maintain the communication continuously?
Thanks in advance!
Regards,
Nico