Date: Tue, 9 Aug 2011 13:32:15 +0200 From: Bernhard Schmidt <bschmidt@freebsd.org> To: Lev Serebryakov <lev@serebryakov.spb.ru> Cc: freebsd-wireless@freebsd.org Subject: Re: Bad host-vased AP performace -- and qouple of questions about FreeBSD WiFi stack tuning Message-ID: <201108091332.16269.bschmidt@freebsd.org> In-Reply-To: <281311475.20110809142033@serebryakov.spb.ru> References: <1151152206.20110808220720@serebryakov.spb.ru> <CAJ-Vmom-VdzRpS0S7c8z3rH5tYkbk1Nadw-=R6r65OX-_AOX1A@mail.gmail.com> <281311475.20110809142033@serebryakov.spb.ru>
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On Tuesday, August 09, 2011 12:20:33 Lev Serebryakov wrote: > Hello, Adrian. > You wrote 9 =D0=B0=D0=B2=D0=B3=D1=83=D1=81=D1=82=D0=B0 2011 =D0=B3., 14:1= 4:19: >=20 > > txpower 15 is actually 15dBm. Ie, try "ifconfig wlan0 txpower 1.5" :-) > Bernhard Schmidt says, that iwn(4) uses half-dBm units and "txpower > 30" on iwn(4) means 15dBm physically. Err.. let me explain that in more detail. The ifconfig txpower command gets its argument in 0.5 dBm steps. That means if you want to set 15dBm you have to use 30, as 30 * 0.5 =3D 15. This is because someone might want to set eg 7.5 dBm but we still want use an integer to store that value. iwn(4) has a "limit" of 15 dBm because it internally assumes that the TX power always relates to all 3 chains being used (11n feature). Each chain does double the output power, to account for that you have to decrease the value by 2 * numchains. So.. setting it 15 dBm results in 15 + 2 * 3 dBm which is around 100mW. The 30 you are seeing is probably coming somewhere else, I assume it is the regulatory limit allowed by that channel. Try playing with different regdomains/countries. =2D-=20 Bernhard
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