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Re: [Discuss-gnuradio] Running tunnel.py/benchmark tx.p y (OFDM) with XC

From: mleech
Subject: Re: [Discuss-gnuradio] Running tunnel.py/benchmark tx.p y (OFDM) with XCVR2450?
Date: Wed, 01 Feb 2012 12:25:25 -0500
User-agent: Roundcube Webmail/0.5.1

The XCVR2450 hardware is incapable of full-duplex operation.  It *cannot* transmit and receive at the same time.



On Wed, 01 Feb 2012 18:05:53 +0100, Florian Schlembach wrote:

We are now trying to establish an TCP/IP connection between both USRP2s with the tunnel.py script. Unfortunately, it says "Destination Host unreachable" when pinging the other USRP. We should have set up the tunnel correct as some packets are received and transmitted after having configured the IP address. The pinged USRPs is indicating the received icmp packet but there is still no confirmed ping-request though.
Short answer; dont do that. Yes, this particular USRP is a network device, but that is completely unrelated to the purpose of tunnel.py. You probably have to play with routing tables to make this work...
Why is that unrelated to the purpose of tunnel.py? Shouldnt a simple ping request be a basic application of using this TUN/TAP application? Anyway, we have now set up the routing table correctly by using TUN instead of TAP. As we are transmitting the ping from one of the USRPs, we are also receiving them at the RX-USRP which is answering with a ping reply: RX-USRP: - TIMEOUT Rx: ok = True len(payload) = 84 Tx: len(payload) = 84 send now! UTIMEOUT - Observing the IP dataflow via Wireshark (at RX-USRP) confirms that. However, we are NOT receiving this ping reply and the transmitting USRP. It seems, like it cannot transmit and receive simultaneously. Exactky the same happens if we swap the role of transmitting and receiving USRPs. Anybody has an idea how we could overcome this problem? Basically, we want to measure the latency of a "real" application. _______________________________________________


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