Cross Channel Interference

Answered Question
Mar 23rd, 2009

Hi,

I would just like my suspicions confirmed. We are using 1131 LWAPP APs, with a 4402 controller. In this particular install, there are around 20-30 laptops within very close proximity to each other, this will obviously create cross-channel interference from the laptops themselves. The customer has reported very slow network speeds and drop-outs when more than 10 laptops are running, but less than 5 seems to be okay.

It seems that the laptops are also associating with the same AP although there are 3 within the area. The only way to control the association that I can see is MAC filtering, in which case they might as well have wired machines.

Is this correct?

Thanks.

I have this problem too.
0 votes
Correct Answer by jeff.kish about 7 years 8 months ago

You are correct, clients provide just as much interference as APs, and sometimes even more. But even then, a single Cisco AP can handle up to 20-25 APs without problems normally.

Try enabling Aggressive Load Balancing on your Controller tab in the controller GUI. This option will actively disconnect clients if too many associate to a single AP. A controller will always do its best to load-balance, but allowing it to disconnect clients will give it more options in doing so.

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Correct Answer
jeff.kish Mon, 03/23/2009 - 07:13

You are correct, clients provide just as much interference as APs, and sometimes even more. But even then, a single Cisco AP can handle up to 20-25 APs without problems normally.

Try enabling Aggressive Load Balancing on your Controller tab in the controller GUI. This option will actively disconnect clients if too many associate to a single AP. A controller will always do its best to load-balance, but allowing it to disconnect clients will give it more options in doing so.

Leo Laohoo Mon, 03/23/2009 - 15:12

1. I'd check for Client Profile Threshold. Go to Wireless, click one of the radios on the left and go down to General and look at "Clients (1 to 75)". Default is 12.

2. The higher number of people associate to one particular AP, the slower the bandwidth. Have you considered putting another AP?

dennischolmes Mon, 03/23/2009 - 20:06

The use of either of these will cause excessive time in roaming between APs as the method of relocating the client to a different AP is the use of disassociation packets. I would assure that proper roaming tendencies are enforced on the client devices. I would also look to the applications being run on the network. If a very high bandwidth application is being run then I would look into 802.11n APs like the 1142.

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