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Hello,. I am curious what others would do in a situation where you have issues with high channel utilization in the 5Ghz band on some of your access points. AP density is high, prob one AP every 20-30 ft in a staggered pattern for the most part. Some areas have them in a straight line. RF tuning has been done to reduce overlapping coverage and DFS channels are being used. The scenario is a high traffic retail environment so the user density plays a significant role. Roaming is working fine so clients are not sticking to access points. It's just the areas where users are concentrated are getting baked out.

Is this a real or hypothetical situation ? 

What is the venue ?  How many users are associating to each AP ?  Have you identified any interference sources?   If dual mode AP's are installed, are you utilizing both bands ?

Do you have the ability to throttle (limit) the throughput of individual client devices?   I assume this is a free network - if so, users can't expect unlimited free service.

Are there certain apps, or streaming modes that you can deny ?  particular game sites, ports, etc.  ?

What is the capacity of the various Ethernet links, and are any of them having problems (e.g. 100 Mbps links) where they should have been Gigabit?   Are you using RRM on a daily basis, and is it causing your problems ?

Are you totally in control of the RF environment, or do you share it with uncooperative neighbors ?   Are some of them using IPS/IDS systems illegally ?

Hello, thanks for responding. This is a real situation that I am still trying to get "tuned up" so to speak. APs are all dual mode. 2.4Ghz is disabled on some access points to reduce interference, but the main issue we are seeing is with the 5GHz band. I believe most of the interference is from neighboring APs. No rogue devices. I also implemented DFS channels to open up the spectrum a little more. When I first became involved with this issue they were just using the U-NII-1 and U-NII-3 5Ghz channels and they were getting slammed. We do get some bleed over in some of our locations from other retailers, but for the most part that is not an issue. We control our environment 100%. At this time we are not filtering or policing anything on the free wifi side and I suspect this is one of the factors in the issue. I have not been given the OK to restrict anything so far. I wont rule out foul play, but since it's intermittent and tends to move around I suspect it's more of a design/tuning issue.

RRM/ARM is being used and is currently how the channels and power setting are being managed. I reduced the min and max power the access points are allowed to use, but intend to reduce it more if allowed as I am still seeing a lot of dynamic changes happening because of interference. Further evidence that this needs to get tweaked or move to a static plan is that I have seen APs with no clients that are reporting above 80% channel utilization. 

Client counts vary, but the most I have seen on one radio is around 50. Certain areas will consistently have more clients, like the checkout and front end areas. The main pathways will as well since that is where the higher concentrations of users will be. We can't implement any kind of client matching features as the legacy devices in the stores do not play well with that. 

I believe that the immediate steps are to get the APs tuned properly to reduce the interference between them. I have had to go to a static channel plan in similar environment with this level of AP density, unsure if I need to or will be able to do that in this scenario.

For high density guest network I would suggest 20MHz channel width also on 5GHz. That will give you twice the number of channels to alternate so you'll get more distance between APs on the same channel.

You should also dig deep into your RRM/ARM if you intend to use it. Most of them still try to max the transmit power. Clients paying for the equipment love to see full bars on their devices so let them – goes the reasoning. For example Cisco has TPCv2 for dense deployments, but you need to know to set it. You should also set the max power on par with the least powerful supported client device. Typically that is around 14dBm.

I don't like RRM but some clients have bought the idea and paid for it, so they insist on it. You can use RRM but keep it in tight control.

Here is a Cisco white paper: https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_RRM_White_Paper/b_RRM_White_Paper_chapter_0101.html

Regarding RRM, here is a CWNP post that bring up some ideas for you.   Devin's webinar, also referenced here, has some extremely good information:

https://www.cwnp.com/forums/posts?How-does-RRM-really-work-124296

I would also provide only 20 MHz wide channels, as Petri mentioned.