[Discuss-gnuradio] Problem with TDD operation

[yend B.]

Hi,

I was trying to implement a TDD system using UHD  time stamp feature. I used the UHD API 
directly (not gr_uhd) to test it first. The transmit path sends bursts periodically, and the receive path
captures all the time. For comparison, I have also recorded the signal from another USRP N200
receiver. The first problem I observed was that few bursts following the FIRST burst
are always lost. Pictures below are snapshots of received signals by the receive path (a) and the 
separate receiver (b)
(a)

.

(b)


The second problem is that the receive path does not capture the transmitted signal (c) unless
the USRP box is power restarted. Flushing the receive buffer with the following command
did not fix the problem.

...
while(true) {
        num_smpls = rx_stream->recv(buffs, 
                    rx_spp,
                    md);
        if (md.error_code == uhd::rx_metadata_t::ERROR_CODE_TIMEOUT)
            break;
    }
...

Your help would be appreciated.

Best Regards!

Beyene