I'm trying to figure out if i need to start tweaking my contention slots to smooth out performance on the sectors especially on the sectors that we've started to get into the 50+ subs.... We started with 3 contention slots but now wonder if we should move higher possibly.
I know auto-tuning of contention slots is coming in the future (dear god i cant wait for that especially can't wait to see how you guys manage cross-cell auto balancing) But i'm worrying about it now :)
I noticed in the frame utilization statistics i'm seeing....
Contention Slots :
132227
Contention Slots Average Per Frame :
5
Does that mean that i'd possibly be better with the contention slots increased to 5?
This is a great question and one that has existed since the beginning of Canopy. :)
In general, with 50+ SMs I recommend more than 3 control slots, but I don't have (and don't like) blanket answers based solely upon SM count, as it also depends on how much uplink traffic you have, channel bandwidth and your downlink data percentage. (And with Uplink MU-MIMO on 450m even another variable!)
Yes, you are looking at a very important stat "Contention Slots Average Per Frame." This is showing you that averaged over that Frame Utilization time period you had 5 open slots on average. You said you have 3 contention slots so that means you only have 2 other uplink slots on average that aren't being used. And remember that unused uplink slots will also be used as contention for that frame. So you're uplink is surely running very full.
Another stat to look at is the percentage of Bandwidth Request Percentage. This is the percentage of Bandwidth Request messages that made it from the SM to the AP in the contention space. The more uplink traffic you have, the more bandwidth requests that are sent and the more collisions you will have with other SM's bandwidth requests.
However, I don't have fixed guidelines to tell you that X% need more contention slots. In fact, I have a report of today of a 15.1.3 system that's showing low numbers (65%) without a lot of uplink traffic. This is something we are still needing to investigate.
I too am really excited for Auto Contention as I'm hopeful for automatic and dynamic optimization of this I think will really help sectors.
Regarding "cross-cell auto balancing" that's not something that's planned for the Auto Contention feature specifically, but something that should definitely be considered.
Disclaimer: Of course remember that changing the Contention Slots does slightly change your frame configuration, so change it on all your APs or use the Frame Calculator Tool to make sure you aren't overlapping your Tx/Rx with other APs.
So for example, I have been having issues on a sector with under 30 people on it, However I am showing 43 slots on average. I to only have 3 slots running now. Is this something that seems out of line or ok? I am on the newest stable FW.
