Radio Profile - channel selection auto - neighbor APs on same channel & running at Max power allowed.

[w1f1n00b]

I’ve been seeing many instances where APs are on the same channel as their neighboring AP with RSSI in the 60s or 70s. I’m looking for steps to take to prevent this that don’t require manual channel plans, as I have too many APs to manage in that manner (wish this wasn’t the case).

In this one example I’m trying to figure out why the two radios are showing drastically different channel costs. full disclosure, not really sure what these numbers mean or how they’re calculated so any info or resources are greatly appreciated.

Also of note, these Radio Profiles are set to auto power selection with max power of 14dB. There are 50+ APs at the site (apx every other room), yet every AP is running at power 14. none have adjusted power down at all. Is this typical? My understanding is that even if Co-channel and adjacent channel interference are minimized, RF should still be kept to minimum power necessary to avoid general interference.

[w1f1n00b]

I’d love to, but I stopped using DFS channels recently after being told by GTAC that radios will not perform background scans while on a DFS channel, effectively making it blind to ACSP (even worse if using “use last known channel/power as they’ll never evaluate the channel they’re on or the neighborhood). They’re set to adjust between 12a-6a so plenty of time there.

Examples above are AP550. I also have a lot of AP250 & AP230 all running 10.x. I have less of the 120,330,350,390 running 6.5r12

Curious what your experience is with MU-MIMO, as this is the first time I’ve seen it recommended. Its off by default, and my understanding was it was only ideal in large venues like stadiums, gyms, auditoriums etc.

I had “skip background scans when clients are connected” checked for a while as I suspected it may be causing client issues, however I’ve since unchecked that at the recommendation of GTAC. main problem I have is with clients that are online/connected 24/7 due to being in charging carts etc. Curious what your experience is with this was well.

@jose.gonzalez I appreciate your feedback, and am always looking for was to improve my environment.

[jose_gonzalez]

I recommend use the DFS channels so ACSP has more channels to choose from.  Make sure ACSP is able to scan radio channels regardless of number of connected clients during a time range, like 12:00a to 4:00a, in the radio profile settings.  Set radio transmission power floor to 2, power max drop to 18.  You haven’t said what model AP and HiveOS version?  8.2r6 / 10.x is better at channel selection than 6.5, however the former use more CPU, can be a issue with large LANs and APs (AP2x0/3x0) management is on the same network.  In addition I recommend you enable MU-MIMO to improve performance and disable allow bgscans with clients connected.  Clients have to be disconnected in order for bgscan to run.  Safest is bgscan only with no clients connected.

Regards,

[w1f1n00b]

If Co-channel interference is “the top cause of needless airtime consumption “ (https://www.extremenetworks.com/extreme-networks-blog/whats-the-biggest-cause-of-co-channel-interfer... ) and it’s often recommended to have 20dB RSSI channel separation (https://www.metageek.com/training/resources/adjacent-channel-congestion.html), that leaves this area as an issue for any client not connected to ch48 at better than -46dB RSSI.  I haven’t surveyed this particular location, but I think it’s save to say this separation would become even less likely for clients located in between these two APs on ch 48.

Given all that and my current understanding, I’m trying to wrap my head around how having two radios on the same channel so close to each other isn’t a problem?

Also of note, channels 44 & 153 aren’t even being used by any APs in the area. Any ideas why this would be?

[SamPirok]

Thanks for that output, those are the background settings I’d recommend so we’re good there. We got some of our senior engineers to review the output you’ve shared and it doesn’t look like the APs would need to lower their power at the moment. We usually don’t see issues until we hit the -50’s RSSI range and up, so those -66 RSSI values on channel 48 shouldn’t be causing any issues. From the outputs you’ve shared here, it looks like the radios are balancing properly at the moment. 

As for the disparate channel cost values, if the AP is acting in dual 5GHz mode it’ll split the 5GHz channels between the two radios, so it’s likely that the higher channel costs are associated with the channels that radio is leaving for the other radio to use instead. 

[w1f1n00b]