Re: [USRP-users] time division duplexing (TDD) with USRP B2xx

[Martin Braun]

Ali,

most of the time, these types of applications require the RX to be on permanently (unless you know exactly when you're expecting packets), and the TX only when you're transmitting packets.

In GNU Radio, this is simply achieved by using a USRP Sink and Source, respectively. The USRP Source (RX) will be permanently receiving into your custom DSP blocks. The USRP Sink (TX) will only transmit when it gets data, so all you need to do is send it data when you have some. Important: You need to add the "tx_eob" tag. See the manual: https://www.gnuradio.org/doc/doxygen/classgr_1_1uhd_1_1usrp__sink.html#a244302d311f9232dc0634ebb920508c7 (look for "bursty transmission").

Note: The TX signal will leak into RX and will appear as a really strong signal. You need to filter those out.

If you're doing vanilla UHD, it's pretty much the same. Except now, you need to pass in the tx_eob tag as metadata (see here: https://files.ettus.com/manual/structuhd_1_1tx__metadata__t.html).

--M

On Sat, Jan 15, 2022 at 11:22 AM Ali G. Dezfuli <ali69550@gmail.com> wrote:

I am going to implement a real-time TDD link (in the order of one-millisecond burst durations) using two laptops and two USRP B2xx (in either single antenna or dual-antenna ways). I searched a lot on the net especially GNU Radio's mailing list but could not find any clear techniques or tutorials to deal with it. So, I wonder if someone helps me manage that in a step-by-step way. Thank you!

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