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Date:  Mon, 14 Nov 2005 00:14:51 +0100
Sender: os2-wireless_users-owner <os2-wireless_users-owner@2rosenthals.com>
Reply-To: os2-wireless_users@2rosenthals.com
From:  Jeroen Besse <os2-wireless_users@2rosenthals.com>
To:  os2-wireless_users@2rosenthals.com
Subject: [OS2Wireless] GenMac, channels and IRQ load

Hi,

Some observations, done with my Atheros (168c,1014) card.

Since the new xwlan, when using the genmac driver, can list all
available networks, I tried to find out whether I should switch
channels.

XWLAN reports neighbour networks at channel 6 and 11. I was using
channel 4 (it gave me the best signal with my previous .11b card).
Looking at <http://www.unixwiz.net/images/80211bchannels.gif>, I
decided that channel 1 would be the best for me, as that doesn't
interfere with my neighbours.
After switching, I noticed that the IRQ load (as reported by eCenter
Pulse) went up to more than 40%, and it stayed high!

So I did some tests.
Test environment:
- Access Point: Linksys WAP54, WEP-128.
- Laptop: IBM T40 with Atheros card, GenMac 1.0, XWLAN 2.0, no
applications running.
- Distance: about 18m, only thin walls.
- Signal strength: about 60-65% continuous during testing.

I then changed the channel on the access point, and watched the IRQ load.
Results (channel - average IRQ load, all were varying +-2%):
1 - 45%
2 - 55%
3 - 75%
4 - 5%
5 - 15%
6 - 10%
7 - 20%
8 - 3%
9 - 10%
10 - 5%
11 - 8%
12 - 4-40% (no connection)
13 - 2% (no connection)

When running applications like Firefox and Thunderbird, IRQ load
became higher. With channel 2, Firefox built its pages very slow. With
channel 3, Firefox even did not show any page.

I don't know why the IRQ load is so different for different channels.
I switched to channel 8, and am happy now.

I hope this information can be of use for others; if you experience
high IRQ loads, test different channels to see whether you can lower
that load.

Best regards,
Jeroen Besse
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