Bad host-vased AP performace -- and qouple of questions about FreeBSD WiFi stack tuning

[Bernhard Schmidt]

On Tuesday, August 09, 2011 12:20:33 Lev Serebryakov wrote:
> Hello, Adrian.
> You wrote 9 августа 2011 г., 14:14:19:
> 
> > 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 = 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.

-- 
Bernhard