Slow connection after Software upgrade on WLC 5508

natuan · ‎11-15-2017

Hi everyone,

We have a WLC 5508.

A few days ago, we upgraded software version from 8.0.120.0 to 8.2.151.0. After that, the connection was slow (<1Mbps for b/g/n devices and good with ac devices)

I searched some documents and support topics but I got no idea to fix it.

Has anyone have the similar situation?

Leo Laohoo · ‎11-15-2017

@natuan wrote:

After that, the connection was slow (<1Mbps for b/g/n devices and good with ac devices)

This sounds like co-channel interference.

What happens if the clients are connected to 802.11a radio?

What data rates are enabled on the controller?

natuan · ‎11-15-2017

Thank you.

We do not use 802.11a and we did not change any configuration so I think data rate is not a problem.

We will check all channels for interference.

I capture a screenshot. Can you take a look at it?

Leo Laohoo · ‎11-15-2017

@natuan wrote:

we did not change any configuration

I disagree. You upgraded from 8.0.120.0 to 8.2.151.0. That's already a change in configuration and behaviour of the controller/wireless. The APs will need to re-tune their radios.

@natuan wrote:

We do not use 802.11a

802.11b is a very congested frequency with 3 non-overlapping channels to use. If this network is in a very dense neighborhood where everyone has 802.11b blasting through the air, then anyone's wireless network is useless.

If you have all data rates enabled and you have high co-channel interference then there will be very, very low airtime. With a low airtime the wireless clients have to significantly demodulate themselves so they can push traffic across. And if you've got wireless clients transmitting at <1 Mbps, then there is a serious chance of high co-channel interference.

And NOT running 802.11a is not a good idea (unless there is a law prohibiting 802.11a) and it will just make matters worst.

natuan · ‎11-15-2017

Thank you for your help. I will check all channels and data rate.

Hope we can fix it.