Wireless clients connect to a distant AP with a much weaker signal and have connectivity problems as a result

[mulugojjam abebe]

Good day,

I have around 15 Cisco 1231 autonomous wireless APs(Ios ver 12.3(2) JA) installed in the yard to serve wireless clients back to the wired network. It was working very good previously, but these days more clients are connected to one specific AP even though there are other APs in nearby.

All the configurations are similar in each APs with different channel numbers and configured for 802.11G.

Any thoughts what cause the clients to connect to a distant AP with a much weaker signal and have connectivity problems as a result?

Thanks,

Mulu

[Leo Laohoo]

Any thoughts what cause the clients to connect to a distant AP with a much weaker signal and have connectivity problems as a result?

Wireless drivers of the client is the a major suspect. 

Another reason is co-channel interference. 

[mulugojjam abebe]

Thank you Leo for your support,

The channel utilization is less than 30%in each channel and these settings were working for long time. This issue started recently.

I wonder why most of the clients connected to one specific AP though everything is similar with the other APs.

Thanks,

Mulu

[Scott Fella]

Here is my 2cents... The AP's are very old, have you tried to test to see if the AP's are not going bad?  When you say yard, is this outdoor or indoor?  It might be time to maybe replace that or swap it out with another AP that is less utilized and see if at least you can improve that area. 

-Scott

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[mulugojjam abebe]

Thanks Scott,

Yes the APs are too old and need to be replaced. But I want to make sure if the issue is related to the APs age or channel interference, antennas....

And they are outdoor APs.

Thanks,

Mulu

[Scott Fella]

So the issue can be environmental. Antennas could be going bad and or the radios.  Testing the AP(s) to verify that you can associate and see what signal you obtain is the key. Compare that with other AP's to get a baseline and that would help to understand if it's the AP being the issue. Associating to the AP and seeing how far out you can go and looking at your signal will also provide you with great info.

-Scott

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[mulugojjam abebe]

Right. The signal strength of this AP is lower than the others, but clients prefer this AP even if there are other APs nearby.

The radios are working in all APs. Clients associated to these APs sometimes but most of the time they disassociate and roam frequently to that distant AP.

Thanks,

Mulu

[Scott Fella]

If you believe that the AP's are working fine, the other issue can be how the devices roam. You can disable lower data rates if you notice that devices tend to stick to AP's and not roam to the closer AP. Remember that the client devices make the roaming decision and what AP's they will associate to. Know what your devices are and disable the lower data rates and make the basic rate higher like 11mbps or higher is you know you have coverage. You can try setting the lowest basic rate at 5.5 Mbps or 11 Mbps and verify that your devices can associate properly. If you have old devices that are 802.11b, you will really have to test as some of these devices still require the low data rates to associate properly.  Changes to the data rates can help devices roam to closer AP's.

-Scott

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[mulugojjam abebe]

Thank you that might be the case. Right now the minimum data rate is 2M. I will change the data rate and try it.

Thanks,

Mulu

[Scott Fella]

Yeah... I would then change that and use the highest data rate that works. This way you can sort of control the coverage for that AP which helps with client distribution. Using a higher data rate also frees up the RF since management frames will be sent at the lowest basic rate.  Make sure you test with devices that are important or used the most. This way you can determine what rates to set. 

-Scott

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