Re: [Discuss-gnuradio] USRP2 + WBX: Half Duplex

[Marcus D. Leech]

On 02/26/2016 12:58 PM, Martin Braun wrote:

Everyone who implements half duplex modems runs into this issue sooner or later. A simple fix is to catch this in software, e.g. On your Mac layer by filtering for your own transmit Mac address (or whatever equivalent you have in your protocol). You can also cache the timestamps of your tx packets and use that to ignore rx packets.

Cheers
Martin

That's precisely what our MAC layer used to do on packet radio, as I recall--ignore any packet that has our own MAC address in the
  source field.

On 26 Feb 2016 07:25, "Marcus D. Leech" <address@hidden> wrote:

On 02/26/2016 07:00 AM, Alex Weihkopf wrote:

Hello,

 

I am using two USRP2 + WBX connected via cable on the TX/RX antenna ports. I want to use them for my GNURadio OFDM-project in half-duplex mode.

 

Problem: Whenever I send a data-packet (~10ms) on the TX-chain of one USRP2, I receive the same packet on the RX-chain of the same USRP2. The transmitter receives its own packets.

 

Why is that? Insufficient Decoupling between Receive and Transmit Circuit?

 

Does the USRP2 internally turn off the Receive Circuit when the Transmit Circuit has data to send? Or does it just disconnect the Receive Circuit from the antenna?

 

Is there a comprehensible GNURadio example for USRP2 + WBX in half-duplex-mode?

 

Regards,

Alex

 

 

 

The RX chain is not disabled, only switched-away from the TX/RX antenna.  There's about 40+dB of isolation between the two sides,
  but that still produces a fair amount of signal at the RX.  The best way forward is to simply ignore RX traffic while you're TXing.

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