On Fri, Nov 19, 2010 at 11:22 AM, Vinod Kone <vinodkone@xxxxxxxxx> wrote: > Hi Luis, > I saw that you posted a message a year ago about tshark's average > computation of signal strength being off. I am facing the same error, and > was wondering what your fix was. I have no fix, but the bug was likely in tshark. Luis > From: "Luis R. Rodriguez" <mcgrof@xxxxxxxxx> > Date: Fri, 19 Jun 2009 17:49:45 -0700 > > > Using tshark from svn (today) with ath5k from wireless-testing (today) > I'm noticing some reporting of a signal value which is completely off > when using the statistics feature (io,stat). At first I though it was > ath5k so I went to verify we don't report huge signal values and we > don't. Right before we hand of the skb to mac80211 I added checked the > signal value and in all cases it was negative and with in reasonable > range -- my awk script says -55.219, for instance. > > Now if I apply the same awk scrip to the output of 'tshark -V -i moni0 >> dump' and then grep for "SSI Signal" I get a reasonable average. > This at least allows me to rule out a driver issue. > > Instead of running awk scripts I'd like to just use tshark to compute this. > > tshark -i moni0 -q -z > "io,stat,1,AVG(radiotap.dbm_antsignal)radiotap.dbm_antsignal,AVG(radiotap.datarate)radiotap.datarate" > > This prints the average signal and rate every second, if you use it > you'll see the first column is gross: > > Capturing on moni0 > ^C1355 packets captured > > =================================================================== > IO Statistics > Interval: 1.000 secs > Column #0: AVG(radiotap.dbm_antsignal)radiotap.dbm_antsignal > Column #1: AVG(radiotap.datarate)radiotap.datarate > | Column #0 | Column #1 > Time | AVG | AVG > 000.000-001.000 14035780 4 > 001.000-002.000 16085960 4 > 002.000-003.000 16976095 5 > 003.000-004.000 19088682 5 > 004.000-005.000 19792417 5 > 005.000-006.000 49367380 5 > > > If I decrease the interval to 0.001 I get more reasonable values: > > tshark -i moni0 -q -z > "io,stat,0.001,AVG(radiotap.dbm_antsignal)radiotap.dbm_antsignal,AVG(radiotap.datarate)radiotap.datarate" > > 5 packets captured > > =================================================================== > IO Statistics > Interval: 0.001 secs > Column #0: AVG(radiotap.dbm_antsignal)radiotap.dbm_antsignal > Column #1: AVG(radiotap.datarate)radiotap.datarate > | Column #0 | Column #1 > Time | AVG | AVG > 000.000-000.001 -40 2 > 000.001-000.002 -41 2 > 000.002-000.003 0 0 > 000.003-000.004 2147483602 3 > 000.004-000.005 0 0 > 000.005-000.006 0 0 > 000.006-000.007 0 0 > 000.007-000.008 0 0 > 000.008-000.009 0 0 > 000.009-000.010 0 0 > 000.010-000.011 0 0 > 000.011-000.012 0 0 > 000.012-000.013 0 0 > 000.013-000.014 0 0 > 000.014-000.015 0 0 > 000.015-000.016 0 0 > 000.016-000.017 0 0 > 000.017-000.018 0 0 > 000.018-000.019 0 0 > 000.019-000.020 0 0 > 000.020-000.021 0 0 > 000.021-000.022 0 0 > 000.022-000.023 0 0 > 000.023-000.024 0 0 > 000.024-000.025 0 0 > 000.025-000.026 0 0 > 000.026-000.027 0 0 > 000.027-000.028 -64 2 > =================================================================== > > But notice that big fat 2147483602. And this is just 5 packets, if you > let it sit for a few seconds you'll see a lot of these spread out and > that ruins the average computation. > > I'd send a patch but I'm not yet sure where to poke. If you are aware > where to look at let me know and I'll check it out. I'd like to fix > this or see this fixed. > > Luis > > Thanks, > -- Vinod > -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
