We're experiencing complaints about drops and spotty performance that improves as users go home and it got me thinking since these are lower end AP's that it could be the number of people connected to them. This week we have training customers in , so our average of ~20 people connected on all WAP's has moved up to about ~60 per WAP.

The environment contains 6 Autonomous WAP's (Cisco 1142's), 3 on each end of the building, with enough overlap to allow seamless roaming between all 6. We have two SSID's an internal and an external / public facing one. The training customers are using the public SSID, the users complaining about performance are on the internal one. The common line here is that the bulk of the training traffic is on 'WAP-5', and the internal users complaining, their stations associate with 'WAP-5'.

My question is: What can I do, to assess a situation like this to determine if the issue at hand is saturation on the WAP and not other external factors like interference / configuration issues / client side issues. I want to clear this off of my list before I dig further into other issues.

EDITED: Reworded question, gave more detail per YLearn's comment.

  • 2
    Too many unknowns to answer this...for instance, what kinds of traffic, how much bandwidth per user, how dense is the AP deployment, what other networks are in the area, how many SSIDs, sources of interference, etc.
    – YLearn
    Feb 5 '14 at 16:01
  • The question's been edited to be more specific as far as assessing a situation. Don't flag this up w/o reading the edit please. It's an answerable question in its current form.
    – A L
    Feb 5 '14 at 17:28

The AP can easily handle 60 clients, but the Wifi channel can't. You have 60 users competing for airtime on a single channel and that's where your interference is happening. Remember 802.11 is a shared medium, so everyone is trying to get their slice of airtime. When clients connect especially at at low speeds, they take longer to send and receive, taking up more of the channel. While one client is sending at a low data rate, everyone else has to wait until they're done

You can lessen the impact by disabling low speeds on your AP. You should disable all speeds below 12M, and possibly all below 22Mb. That will disable 11b clients, which will improve performance. It will also force clients to get on and off the channel much more quickly, improving the channel utilization. The downside is you will reduce the range between clients and the AP.

You can also configure the 1142 to push clients up to 5GHz. that will help a little, but iPhones and most Andriods are only 2.4GHz, so that's of limited value.

There are tools to measure channel utilization, but they can be a little pricey. Fluke and Airmagnet make wifi analyzers that will do that.

  • Ron this is very good information, I really appreciate your thorough response, fascinating to hear about the root of the problem, not just a solution. Marking this as the answer.
    – A L
    Feb 6 '14 at 15:23

You can take a look at the CVDs for Mobility: http://www.cisco.com/en/US/netsol/ns820/networking_solutions_program_home.html

I wouldn't put 200 people on one AP. Try to keep the number low (~30 maximum), and in general with different use charateristics of various WLAN clients, you should get good performance.

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