High Latency on 450AP sector


We have a sector 450 AP with around 26 SM, all was working well  as the traffic increases we noticed high latency, to almost all SM, no matter what is the usage of each sm, this sector was on 38mb / 6mb and now its reaching 45/8 this could be due to high usage, but the 450 platform is advertised as being able to deliver up to 130 aggregate, and we have it set to 75% I am not sure if its the sector capacity or my settings, 

QoS is default, 65/65 

QoS Config from SM. and every sm has a qos of 5 or 10mb. depending on client. 

Contention slot, 4, we incresed to 6 and few SM dropped but no improvement. 

2.5 ms, frame

Teting from most of the SM gives 99% downlink and uplink. and a good 6x/6x or 6x/4x speed. 

Anything we are missing here ? 

thanks for help. 

If you're running the AP on firmware rev 13.4 you can check out your frame utilization stats on the Statistics page. Check it durning peak times and/or when you notice latency occuring across your SM's. If your uplink and/or downlink is reaching 99%, that means that your AP is saturated and you'll either need to:

  • Increase the AP's channel width (if you're not already running 20MHz)
  • Find another channel with less noise
  • Identify those clients with poor SnR/modulation and find ways to improve them
  • If your uplink is reaching 99% but your downlink appears to not be reaching peak, reduce your downlink % until your uplink frame utilization is a lower %... you can do the same thing if your downlink is reaching 99% but you still have uplink capacity available

The '130mbps aggragate' is assuming that you're using a 20mhz channel width and that all clients are regularly achieving 256QAM modulation on the downlink and uplink. This is pretty difficult to achieve in most deployments without very strict installations requirements.

Good luck!

Hi Eric,

Many thanks for the reply, I was trying to make all sort of changes to make the sector survive, but finally decided to add another 450 AP and that reduced the load and now both are working well, it seems that they can only go up to 40 or little higher with the environment i have, and this could vary from site to site. 

I checked the frames and it was around 80% on both cases. but SM connected here would have very poor lateny, even when it was not peak hrs. the addiitional AP is helping at this moment. 

many thanks for the help.