Date: Thu, 8 Sep 2011 12:59:07 +0400 From: Lev Serebryakov <lev@freebsd.org> To: Adrian Chadd <adrian@freebsd.org> Cc: freebsd-wireless@freebsd.org Subject: Re: AP performance (again): txpower regulation Message-ID: <426917282.20110908125907@serebryakov.spb.ru> In-Reply-To: <CAJ-Vmo=R-a%2BqhDLWj1n%2BBj70Pmg4WSL6bVZ6jwCUmNq=v7EBBw@mail.gmail.com> References: <663133681.20110907193747@serebryakov.spb.ru> <CAJ-Vmonai4LzwanLw7i5d-NyjN2b6GqfttjkdcROvOuEcuzEAw@mail.gmail.com> <437702009.20110907235248@serebryakov.spb.ru> <CAJ-Vmo=R-a%2BqhDLWj1n%2BBj70Pmg4WSL6bVZ6jwCUmNq=v7EBBw@mail.gmail.com>
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Hello, Adrian. You wrote 8 =F1=E5=ED=F2=FF=E1=F0=FF 2011 =E3., 8:02:28: > These look fine, but I don't have as much experience with the ar5212 > series stuff as I do with the AR5416+ series stuff. >> =A0It seems, registers are Ok. But clients don't see any difference! >> Maybe, it is because my Senao card is "powerful" one, with additional >> schematic (and power supply) to boost signal? > Hm. Well, how far away are they? You can do a bit of math to see what About 7 meters and 2 concrete (internal) walls :) I've repeated experiment when client and server were within 3 meters without walls -- txpower seems to work. 30 gives about -55dB (accroding to InSSIDer -- I'm not sure, that this numbers could be used as absolute ones),txpower 15 gives about -65 and txpower 1 about -75. But in any case iperf throughput is about 10-11Mbit/s with pikes up to 18= Mbit/s. It looks pessimistic: 18Mbit/s in 2m direct sight. I know, that 54Mbit/s is half-duplex, but 18Mbit/s is less than 27Mbit/s and "ifconfig wlan0 list sta" shows data like this: 00:18:de:08:e8:1d 1 9 36M 21.5 0 28696 48048 EPS AQE RSN = WME Why 36M in almost-ideal conditions!? Why -70dB in room next to my AP, when neighborhood AP (simple d-link, according to all data) is -65, and this room is furthest from other apartments)!? Also, graph of signal strength is much smoother on small distances and didn't look like mountain range. Another observation: when distance is about 5 meters txpower 30, 15 and 10 are almost indistinguishable (and grpahs are smooth, -75dB for 10, -70dB for 15, -67dB for 30), but txpower 1 gives crazy graph: it osscilate between -80 and -10 (!!!). Sometimes it gold on -77, but after 10-15 seconds raise to the sky, then drop down again, etc. > changes the TX power on the sender side would have on the receiver > signal level. > Have you ever looked at doing up a free space loss model to predict > what the signal level(s) should be? It is too complex for me :-) And I'm not sure, that I have tool to measure real signal to compare with calculations. --=20 // Black Lion AKA Lev Serebryakov <lev@freebsd.org>
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