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

[Adrian Chadd]

Hi!

To answer your questions (and ask one of my own):

Can you verify when "bad" and "good" performance occured? Can you
narrow it down to FreeBSD versions in particular?

1) It's hard to tell from the info you've given, please let me know
why/when it worked well some time ago. This is most important.
2) not sure, it's late and I'm not knee-deep in the beacon frame
format. But I bet it's ok?
3) txpower is in dBm units, based on what the card is supposed to be
putting out of the antenna socket, before antennas
4) RSSI is in "dB above noise floor".


Adrian

2011/8/9 Lev Serebryakov <lev at serebryakov.spb.ru>:
> 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>
>
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