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Wireless Access problems/questions:  Signal dropping

Posted on 2006-11-20
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Last Modified: 2013-11-09
I did some side work recently for a very small business which has 4 desktop machines, a DSL modem/router/firewall device, and a  new Linksys Wireless Access Point.  One of the desktop machines is physically connected to the 4 port switch on the back of the DSL router, and the other three desktops have wireless network cards installed.  They originally had a Linksys Wireless ROUTER device, but since the DSL modem had the router functionality built into it (along with a 4 port switch and firewall capabilities), I recommended they simply install an Access point.

So my question is, with the original Linksys Wireless Router, their wireless connections were VERY stable.  Since installing the brand new Access Point, the wireless signal works great for a short while, then seems to drop off...and the computers don't see it any longer.  To fix this, they simply unplug the access point for a few seconds and plug it back in.  The computers automatically reconnect after about 40 seconds, once the access point is powered back on.  The length of time the wireless works varies...from 10 minutes to 10 hours it seems.  But they still have to reboot the thing frequently.

Their office if very small and all three wireless desktops have excellent signal strength (when the access point is working).  They are all very close in proximity to the access point as well...with very few obsticles between them.  When the wireless signal goes out...all the computers loose their connection at the same time.

Is this simply a case of a bad access point?  Normally, I would assume that is what is happening, but I have noticed this sort of (similar) behavior in other wireless applications.  For example, another person I know has a wireless access point at his home.  His laptop will frequently drop the connection and his wife's laptop will always have a great signal and never seem to drop.  The guy will stay connected all day long however in the office or when he is travelling...it's only on his home access point where he has a problem.  Yet, his wife's computer if just fine with it.  AND, it's only recently that he has had this issue.  I also brought my laptop over to his house, and it stays conneceted perfectly.  I would suspect something has changed on his laptop, but he can use other wireless networks perfectly for long periods of time.

Sorry the question is so long, but I can summarize by asking what are the causes of wireless signals dropping when all other factors are good?

Thanks.
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Question by:jbobst
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rindi earned 200 total points
ID: 17985514
Wireless devices can be put off by many other devices, like wireless phones, fluorescent lights, microwave ovens, other wireless access points in the region etc. If you have a problem with an access point loosing connection, the first thing to do is look for a firmware update and after having upgraded, change the channel. You'll have to do some long term testing with these different channels to find the best for your location. First try the channels 0,6,11, then those in between. You could also get netstumbler which will give some idea of other devices using which channel so you don't use the same. If you are using mixed wireless adapters in the PC, like 11b or 11g or other modes, then it can help to set the AP to only use 11b mode. This of course is a lot slower, but if the main reason for using the lan is surfing the inet, that is more than fast enough.

http://www.netstumbler.com/
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by:jbobst
ID: 17988024
rindi,

Thanks for the information.  I have never quite understood why there are channels on wireless access points...and why they are usually set to channel "6" for the default.  Are the other channels less capable?  I am trying to remember if this access point even had a setting to change the channel.  I don't remember, but I don't think I have ever seen one that didn't.  I'll start there and see what happens.

Thanks.
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by:rindi
ID: 17989338
Not all default to 6. Some I've seen default to 11...

Anyway, the channels are there so you can choose a better one if there is disturbance. Usually you'll get overlaps of +- 3 Channels, so if it is set to 6, you'll have activity between 3 and 9. All AP's I've seen the channels can be set to certain values.
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by:dalesit
dalesit earned 50 total points
ID: 18068217
One of the problems which is arising now is caused by the car alarms of certain manufacturers. These broadcast a continuous tone at 2.450GHz which is halfway between channels 8 and 9 for the internal movement sensors. As this is a continuous tone at 500mW (normal limits for access points is 100mW), it can wipe out traffic on channels 6 and 11 due to the overlapping channels).

This frequency use won't show up in Netstumbler, as it is non-wifi traffic. It simply shows up there as noise (assuming your wireless device transmits this info to Netstumbler). For debugging problems on this I would recommend getting a Wi-Spy from http://www.metageek.net.

More exploration of this problem can be read at <http://www.pateley.net/blog/?cat=2> together with a video of the investigations.

Cheers,

Joel
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