Does WLC change channel of AP if their are active clients?

Lucas Phelps · ‎05-15-2009

Occasionally I receive alerts about some of my AP's are down. From what I see in the logs of WCS is that the WLC is changing the channel of the access point from channel 1 to channel 11 because of interference energy.

Its great that the wireless improves itself, but will it do this if that AP has an active client?

John.Gerlach · ‎05-18-2009

Yes it will.

Obviously there are ways to work around it but it tends to make your network less able to dynamically deal with interference issues. You can turn off the DCA and just trigger it manually, or you can still lock in an access points channel number if it seems to warrant it.

We had a deployment with a high concentration of microwave overs that was affecting wireless and AP channel changes mainly through the lunch hour. We were better off locking two of the AP's nearest that mess to a channel that received the least interference. They still receive fairly heavy interference but it stops the ripple affect of changing channels with the rest of the floor from happening and cut the number of channel changes way down.

Lucas Phelps · ‎05-19-2009

We have a similar situation with our office. It is in a multitenant building in a large office park. So there is a great deal of interference from other close AP's that I had no control off. So occasionally the APs that are in our office, change their channels.

You recommend locking them down to one channel with the least interference?

Or how would you handle this?

John.Gerlach · ‎05-19-2009

The decision to lock your AP's to a particular channel may depend a lot on your environment at this location. How many AP's are at this location and potentially might ride the channel changing wave? How many "rogue" neighbors with reasonably strong wi-fi signals do you have? At some of our locations we pick up a lot of local residences adjacent to our locations but the SNR is < 10 so I typically don't concern myself too much with that. But neighbors with a high SNR are the ones you will want to try to work around. If the channels they are using are well-chosen (i.e. 1,6,11) then there is hope.

I just realized that I am making the assumption that the 2.4 GHz 802.11B/G band is what you are using. It sure seems that is the most problematic spectrum for me.

And a multi-tenant environment is no fun. Especially when your neighbor can go pick up the latest 802.11N access point from the electronics store and proceed to bond a couple of 802.11B/G channels together to get that great N speed without understanding the side effects on the shared medium.

Once you have a handle on the strongest signals to work around then you might find that by assigning a specific channel to the AP(s) nearest that source you can improve your environment. You may not be able to eliminate the interference but you may be able to contain the effect to one area.

(edited my typos)