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

[Lev Serebryakov]

Hello, Freebsd-wireless.

 I have host-based AP, which is running FreeBSD 8.2-STABLE (i386) and
equipped with Senao EMP 8602 Plus-S Mini-PCI WiFi card. It is Atheros
5413 based 600mW card:

ath0: <Atheros 5413> mem 0xa0060000-0xa006ffff irq 15 at device 17.0 on pci0
ath0: [ITHREAD]
ath0: AR5413 mac 10.4 RF5413 phy 6.1

 I'm using it with 10dBi omnidirectional antenna in 802.11g (2.4Ghz)
standard.

 It worked well some time ago, but now its performance is horrible.

 Main clients are Intel-based notebooks with Intel 3945ABG cards,
Windows-based.

 Typical "Real" (file copy) bandwidth with only one client active is
500-600KiB/s. Windows shows "Excellent" signal level and 54Mbit.
InSSIDer (Windows-based WiFi monitoring software) shows RSSI between
-50 and -40 (dBm)m but I can not trust it, as it shows some very
distant APs with RSSI 100-120 (yes, +100 - +120), and it is nonsense.

 I've bring additional notebook with Linux and Kismet installed.
Kismet shows, that my AP oscillate between -80 and -40 dBm RSSI
permanently, even if here is connected (and doenloading!) client
connected. Signal level jumps up and down, and often Kismet receive
frames with broken SSID (one-two chars are replaced by other).

 "ifconfig wlan0 list sta" on AP shows something like this (running in
cycle with "sleep 1", one client copy big file, 600-700KiB/s):

00:18:de:08:e8:1d    1    9  24M 14.5    0  23084  35488 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  18M 11.0    0  23612  39952 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 13.5    0  24116  44320 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 13.0    0  24688  49104 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 13.0    0  25341  54720 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 13.0    0  25813  58640 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  54M 11.0    0  26092  61104 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  54M 12.0    0  26782   1424 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  54M 14.0    0  27241   5312 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 14.0    0  27615   8496 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 12.5    0  27872  10768 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 14.0    0  28302  14432 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 13.5    0  28912  19600 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  18M 14.0    0  29501  24624 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 13.5    0  30305  31440 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  24M 13.5    0  31971  45584 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  36M 13.0    0  32429  49472 EPS  AQE     RSN WME
00:18:de:08:e8:1d    1    9  11M 12.5    0  32758  52288 EPS  AQE     RSN WME

  Also, tcpdump shows, that AP announce only speeds up to 18Mbit (tag
number 1 in beacon frame, list of supported speeds -- 1, 2, 5.5, 11,
6, 9, 12, 18).

 Here is my setting of AP:

ifconfig_wlan0="inet 192.168.135.1 netmask 255.255.255.0 mode 11g channel 9 ssid home.serebryakov.spb.ru country ru regdomain row txpower 30"

 So, Questions are:

(1) Hopping signal strength and total terrible WiFi network
    performance -- is it broken hardware or something strange in
    FreeBSD code?

(2) Why card announce only 18Mbit, but not more?

(3) What "txpower" setting means? dBm is relative unit. My 600mW card
    lists "30" as max, and simple notebook Intel card lists "30" as
    max too. Is it relative to max power of card (100mW for standard
    cards, 400-600-1000mW for high-power "procider-grade" cards from
    Ubiquiti and other such wendors, like Senao) or 1W or 100mW or what?
    Manual pages didn't give answer.

(4) What units are uses for RSSI output in "ifconfig list sta"?

-- 
// Black Lion AKA Lev Serebryakov <lev at serebryakov.spb.ru>