Date: Thu, 18 Jul 2013 17:52:00 +0200 From: Petar Bogdanovic <petar@smokva.net> To: freebsd-wireless@freebsd.org Subject: high latency due to distant clients Message-ID: <20130718155200.GA381@pintail.NGC004>
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Hi, for several years now, I've been running an ALIX-AP with a CM9 Atheros 5212 card. The AP covers a whole house which has about 6 flats and the average amount of active clients ranges from 10 to 15. Recently I noticed high latency when pinging the AP itself which happens when distant clients (who knows where around the house---could be inside or outside) seem to cause "longs" (long on-chip tx retries) and/or "xretries" (tx failed 'cuz too many retries). The Rate, when talking to these distant clients, is usually below 11M (sometimes as low as 1M) which is consistent with their low RSSI values the AP is reporting. With high latency I mean continuous bursts of 500-1000ms instead of 0.5ms so I wonder if this is normal. The software is slightly out of date and athstats is not completely in sync with the kernel i'm using (therefore its not reporting some values): # uname -a FreeBSD parrot.NGC004 8.1-RC2 FreeBSD 8.1-RC2 #2: Thu Aug 16 21:13:54 CEST 2012 # athstats -i ath0 athstats: ath0: Invalid argument athstats: ath0: Invalid argument 3181606 data frames transmit 45659 tx frames with an alternate rate 568149 long on-chip tx retries 19091 tx failed 'cuz too many retries 0M current transmit rate 25 tx stopped 'cuz no xmit buffer 20922 tx frames with no ack marked 3039151 tx frames with short preamble 362335 rx failed 'cuz of bad CRC 1181 rx failed 'cuz of PHY err 315 OFDM restart 866 CCK restart 2 TDMA slot timing updates -0/+0 TDMA slot adjust (usecs, smoothed) 26135 TDMA tx failed 'cuz ACK required -74 rx noise floor 3070927 tx frames through raw api 6299685 fast frames received 1328215 fast frames flushed from staging q 20835 ANI decrease noise immunity 6593 ANI increased spur immunity 121582 ANI decrease spur immunity 160 ANI decreased first step level 2 cumulative OFDM phy error count 2 RTS without CTS 1360093 beacons received Antenna profile: Any ideas on how to avoid that? Of course I could buy better antennas but it seems that, generally speaking, this shouldn't happen. Thanks, Petar Bogdanovic
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