[maemo-developers] WLAN Horrible Roaming Performance (N800, OS2008), Software or Hardware Problem ?

[From: Jan Vachun]

Benno Senoner wrote:
> 2008/2/14, Kalle Valo <kalle.valo at nokia.com>:
>>>> Most probably the connection would recover after a while, and the
>>>> while here being several minutes with the default TCP settings.
>>>
>>> You think those time outs are really that long ?
>>
>> Yeah, they are quite long. I have heard about long timeouts with other
>> applications using TCP.
>>
>> An easy way to confirm, if this is a TCP problem or something else, is
>> to run ping in the background and see how long timeouts (ie. how much
>> you see packet loss) you get with it. ICMP ping does not have any of
>> problems that TCP has.
> 
> 
> Yes I did and indeed ping works much better.
> i tried ping  -s 1024  mylocalgatewayip
> (1024 byte long packets)
> and indeed it works ok. sometimes it loses 1-4 packets while roaming
> but afterwards the number of packet loss is usually small.
> when roaming around the wlan it is about 3-4%
> but the nokia wlan lockup remains, see below.
> 
>> the strange thing is if I go around the area with my Dell Laptop
>>> (under Windows) with VNC open it does not suffer from those extreme
>>> slow downs.
>> I'm guessing that the laptop is roaming more aggressively than the
>> N800 and TCP works fine because of that.
>> yes could be.
>>
>>
>>
>> I usually run 'iwevent &' to get it running in the background so
>> that I can easily see what's happening. Very handy.
> 
> 
> thanks.
> 
> 
>> Sorry, I made a mistake here! Unit of bgscan_interval is milliseconds,
>> not seconds as I say above. So the correct way to set background scan
>> interval is this:
>>
>>
>> gconftool-2 --set --type int \
>>
>> '/system/osso/connectivity/IAP/bgscan_interval' '20000'
>>
>> I'm sorry about this.
> 
> 
> no problem, thanks, i will try it out.
> 
>> As for the network lock ups we are experiencing (you have to
>>> disable,enable wlan on the n800 to make it work again)
>>
>> Does ping work when that happens? For example, you could try to ping
>> your gateway. Also can you send me the output from dmesg after you
>> experience this, please?
> 
> 
> when it locks up even ping stops responding, I get a message connection lost
> (from maemo).
> I just tested it today with an xterm open running a constant ping and
> walking around the area.
> after 10min it stopped working (I was out of coverage area and returning)
> I did unfortunately not look at the dmesg output, I will try again and
> report my findings.
> 
>> other users reported it too as Luca Olivetti pointed out. and it
>>> seems like the problem and fix is described here:
>>>
>>> http://internettablettalk.com/forums/showpost.php?p=134914&postcount=15
>>>
>>> at least for the 770 the fix seems to exist,
>>
>> What I read from the link, someone had written a workaround to try
>> again whenever the chip is responding. That would good a feature, but
>> I would like to get more information about what's happening in this
>> case.
> 
> 
> i will investigate this issue and will look at the sources of the patch and
> see if
> it can be adapted to the n800 wlan driver (I can ask for help on the
> project's mailinglist)
> i hope it will solve the issue as this problem occurs several times per day
> in my wlan environment.
> 
> 
>> 770 has quite old software, so I would prefer if you can send me more
>> information with N800.
> 
> 
> of course, I will do it, we will buy more n800,n810 for our purposes
> certainly not 770 :
> 
>>
>> With WLAN driver changes ASAP usually means quite a long time due to
>> all the risks, testing and certification involved.
> 
> 
> Yes, but I am willing to run my patched driver if needed, this is not a
> problem.
> I will investigate all the issues and report all my findings.
> 
> PS:
> meanwhile in order to automate WLAN lockup recovey, how could I write
> a script which basically does the same like clickingon the connectivity
> icon,
> basically bring down wlan and then bring it back up.
> I tried with
> ifdown wlan0 ; ifup wlan0
> but it does not work it says no such device.
> any hints ? some commands to send to wcond ?
> 
> thanks and best regards,
> Benno
> 
> 
> 
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I have faced the same problem with rooming. In addition, my situation
was complicated by presence of others wireless networks.
So basicaly I'm using sort of ping over UDP to determine
existence/quality of wireless link.

I'm also using this simple script to force connection to specified
network ( and force disconnect before if it is actually connected to
wrong network ). You can easily adapt it to suit your needs ....

#get authorized network name
E3G_NET=`cat bindata/authorized_network`

NET=`dbus-send --type=method_call --system --print-reply
--dest=com.nokia.icd /com/nokia/icd com.nokia.icd.get_ipinfo | grep
string | head -1 | cut -d'"' -f2`
if [ "x$NET" != "x$E3G_NET" ]
then
#  echo disconnecting $NET ....
   dbus-send --system --dest=com.nokia.icd /com/nokia/icd_ui
com.nokia.icd_ui.disconnect boolean:true
fi
#echo connecting to #E3G_NET
dbus-send --type=method_call --system --dest=com.nokia.icd
/com/nokia/icd com.nokia.icd.connect string:"$E3G_NET" uint32:0

Hope this can help ....

  Jan

-- 
Jan Vachun

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