How do I know if I am running in full duplex for tunnel.py? Is there a command line argument for that? I think I am running half duplex only since only using the 1 antenna port. If I am running half duplex then I am unsure why I would be having reflected packets.
Message: 25
Date: Thu, 20 Oct 2011 11:24:04 -0400
From: "Marcus D. Leech" <
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To:
address@hiddenSubject: Re: [Discuss-gnuradio] USRP2 / Tunnel.py packet reflection
issue
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On 20/10/2011 10:25 AM, David Barton wrote:
> I have been troubleshooting an issue with possible packet relflections
> and cannot figure out the cause. I am running tunnel.py on two USRP2s
> that are cabled together with a 20dB attenuator between them. The
> settings I am using on both sides for tunnel.py are:
> Tx Gain: 15 dB
> Rx Gain: 10 dB
> Carrier Threshold: -80
> Rx Tunnel Freq: 400 MHz
> Modulation: GMSK
> Bit Rate: 1Mb/sec
> When I use VLC to stream a video from computer A to computer B over
> the USRP link it works ok but there are alot of reflected packs being
> recorded by computer A. The same thing happens when I try to stream
> from computer A to computer B. This also occurs when I use iperf to
> test the link. Strangely, though there are NO reflected packets when I
> ping between the computers.
> Below is a paste of some of the output from computer A. I put in a
> timestamp on the left of when events occur. I also put in an explicit
> statement to print out when tunnel is backing off and for how long. I
> added sequence number to make it blatantly obvious that the computer
> is receiving its own packet. Any packet with a sequence number
> beginning originates from computer A. If the packet originated from
> computer B it shows up at RX_packet=none. As it shows computer A is
> receiving its own packets!
> [ 63.61 ] Tx: seq_no = 100054 | len(payload) = 1448
> [ 63.61 ] Tx: seq_no = 100055 | len(payload) = 186
> [ 63.61 ] Tx: seq_no = 100056 | len(payload) = 1310
> [ 63.61 ] Tx: seq_no = 100057 | len(payload) = 1448
> [ 63.61 ] Tx: seq_no = 100058 | len(payload) = 1021
> [ 63.61 ] Backing off for 0.001 sec
> [ 63.62 ] Backing off for 0.002 sec
> [ 63.62 ] Backing off for 0.004 sec
> [ 63.63 ] Backing off for 0.008 sec
> [ 63.64 ] Backing off for 0.016 sec
> [ 63.64 ] Rx: ok = True | seq_no = 100054 | len(payload) = 1448
> [ 63.66 ] Backing off for
0.032 sec
> [ 63.64 ] Rx: ok = True | seq_no = 100055 | len(payload) = 186
> [ 63.66 ] Rx: ok = True | seq_no = 100056 | len(payload) = 1310
> [ 63.66 ] Rx: ok = True | seq_no = 100057 | len(payload) = 1448
> [ 63.67 ] Backing off for 0.064 sec
> [ 63.67 ] Rx: ok = True | seq_no = 100058 | len(payload) = 1021
> [ 63.72 ] Tx: seq_no = 100059 | len(payload) = 1448
> [ 63.72 ] Tx: seq_no = 100060 | len(payload) = 70
> [ 63.72 ] Tx: seq_no = 100061 | len(payload) = 1448
> [ 63.72 ] Tx: seq_no = 100062 | len(payload) = 150
> [ 63.72 ] Tx: seq_no = 100063 | len(payload) = 1448
> [ 63.72 ] Tx: seq_no = 100064 | len(payload) = 248
> [ 63.72 ] Backing off for 0.001 sec
> [ 63.72 ] Backing off for 0.002 sec
> [ 63.73 ] Backing off for 0.004 sec
> [ 63.74 ] Backing off for 0.008 sec
> [ 63.75 ] Backing off for 0.016 sec
> [ 63.74 ] Rx: ok = True | seq_no = 100060
| len(payload) = 70
> [ 63.75 ] Rx: ok = True | seq_no = 100061 | len(payload) = 1448
> [ 63.76 ] Backing off for 0.032 sec
> [ 63.75 ] Rx: ok = True | seq_no = 100062 | len(payload) = 150
> [ 63.76 ] Rx: ok = True | seq_no = 100063 | len(payload) = 1448
> [ 63.76 ] Rx: ok = True | seq_no = 100064 | len(payload) = 248
> [ 63.78 ] Tx: seq_no = 100065 | len(payload) = 1448
> [ 63.78 ] Tx: seq_no = 100066 | len(payload) = 566
> [ 63.78 ] Tx: seq_no = 100067 | len(payload) = 1448
> [ 63.78 ] Tx: seq_no = 100068 | len(payload) = 987
> [ 63.78 ] Backing off for 0.001 sec
> [ 63.79 ] Backing off for 0.002 sec
> [ 63.79 ] Backing off for 0.004 sec
> [ 63.79 ] Backing off for 0.008 sec
> [ 63.8 ] Backing off for 0.016 sec
> [ 63.8 ] Rx: ok = True | seq_no = 100066 | len(payload) = 566
> [ 63.82 ] Backing off for 0.032 sec
> [ 63.82 ] Rx: ok = True | seq_no =
100067 | len(payload) = 1448
> [ 63.82 ] Rx: ok = True | seq_no = 100068 | len(payload) = 987
> [ 63.84 ] Tx: seq_no = 100069 | len(payload) = 1448
> [ 63.84 ] Tx: seq_no = 100070 | len(payload) = 1448
> [ 63.84 ] Tx: seq_no = 100071 | len(payload) = 1448
> [ 63.84 ] Tx: seq_no = 100072 | len(payload) = 321
> [ 63.84 ] Tx: seq_no = 100073 | len(payload) = 1448
> [ 63.84 ] Tx: seq_no = 100074 | len(payload) = 855
> [ 63.84 ] Backing off for 0.001 sec
> [ 63.84 ] Backing off for 0.002 sec
> [ 63.85 ] Backing off for 0.004 sec
> [ 63.85 ] Backing off for 0.008 sec
> [ 63.86 ] Backing off for 0.016 sec
> [ 63.87 ] Backing off for 0.032 sec
> [ 63.86 ] Rx: ok = True | seq_no = 100070 | len(payload) = 1448
> [ 63.89 ] Rx: ok = True | seq_no = 100071 | len(payload) = 1448
> [ 63.89 ] Rx: ok = True | seq_no = 100072 | len(payload) = 321
> [ 63.89 ] Rx: ok =
True | seq_no = 100073 | len(payload) = 1448
> [ 63.9 ] Backing off for 0.064 sec
> [ 63.9 ] Rx: ok = True | seq_no = 100074 | len(payload) = 855
> Does anyone have any idea why this could be occurring? I thought
> maybe it would be a physical reflection but dont understand why ping
> packets would not be reflected in that case.
> Thanks,
> Dave
There's generally only about 45dB of isolation available between TX and
RX, so if you're running in full-duplex, your receiver will see its
own transmissions.
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