2.4Ghz high latency solutions

[Diederik_Kuijpe]

I'm currently experiencing some issues with our wireless network I could use some help with figuring out a solution.

The situation is as follows:

I've two EW C25s and 60 AP-3825is. About every classroom, office and common area has an AP. I've the following configured:

The main wlan SSID (2.4+5ghz) is bridged at the AP and connects to internal resources.
The guest network (2.4+5ghz) is a captive portal bridged at the C25 and forwarded to the gateway.
The BYOT network (2.4+5ghz) is RADIUS auth bridged at the C25 and forwarded to the gateway.
The Chromebook network (5ghz) is bridged at the C25 and forwarded to the gateway.

For the most part this work out fine, but recently I noticed a massive increase in latency on the 2.4ghz main network. This is causing problems with new teacher laptops (2.4ghz b/g/n only adapters in them I'm afraid). Pings between 500-2000ms, and terrible upload speeds. It's causing severe disruptions.

What are some things I should check? I have a feeling this is part configuration and part hardware incompatibility. Does anyone recognize this situation?

[Diederik_Kuijpe]

Auto channel and max 14 dBm/8dBm 2.4/5. Looks like most are on 1, 6, 11; 36 and 44.

There's one rogue AP that's part of a point to point deployment that's somehow broadcasting.

[Jeremy_Gibbs]

Do a packet capture and check for cochannel interference. What is your ap density?

[Diederik_Kuijpe]

I've never done one before. What would you recommend?

Density is one per classroom, some are in closer proximity than others (room sizes differ a lot). I don't really know how else to describe it.