topic Re: flexible radio assignment in Wireless

flexible radio assignment

Moudar — Mon, 22 May 2023 09:34:33 GMT

Hi,

I have a classroom with about 35 devices (Ipads and laptops connecting to 5GHz), when all are connected and students are doing what they have to do, the channel utilization is reaching 80 and 90%. So my idea was to use FRA to share the load on 2 5GHZ radios. AP is 2802 and WLC 5520 running 8.10.181.3

When i manually changed the 2.4 radio to 5GHz everything was fine until the next class that the students had!

I was sitting and watching the AP on the WLC GUI (Access Point View)

The problem I had was that many devices jumped all the time between the two 5GHz radios the students had a very bad experience when that was happening. (The devices were settled, no one was moving around) the AP is placed in the middle of the classroom ceiling.

What is Throughput in the picture above? When all were connected Throughput was about 3 Mb, up and down

Re: flexible radio assignment

Mark Elsen — Mon, 22 May 2023 10:42:08 GMT

- According to https://www.cisco.com/c/en/us/support/docs/wireless/wireless-lan-controller-software/200046-tac-recommended-aireos.html . consider using https://software.cisco.com/download/home/286284738/type/280926587/release/8.10.185.0 (there are a number of bugfixes , check if that can help ,

Re: flexible radio assignment

Moudar — Mon, 22 May 2023 11:16:35 GMT

isa there any specific bug that is about FRA?!

Re: flexible radio assignment

Mark Elsen — Mon, 22 May 2023 11:53:51 GMT

>....is there any specific bug that is about FRA?!
https://bst.cloudapps.cisco.com/bugsearch?pf=prdNm&kw=flexible%20radio%20assignment&bt=custV&sb=anfr

Now that list is indeed a bit 'generic' (indeed) , yet my initial advice remains important because we are 'entering an age' where aireos is getting older because of the new 9800 controller based platform(s). In that context for aireos based controller(s) it becomes more and more advisable (good practice) to go to the latest advisory release (that they can still run).

Re: flexible radio assignment

Flavio Miranda — Mon, 22 May 2023 12:05:59 GMT

My experience with FRA was never good. The behavior you faced is not acceptable of course but even when you dont face a problem like this, I dont like the solution. If I were you I would put another Access Point in the room. Just keep them in different channel and you will be good.

Re: flexible radio assignment

Rich R — Mon, 22 May 2023 15:37:43 GMT

Agreed with Flavio - roaming between radios is client behaviour so there's not much you can do to control it. On laptops, depending on what the network driver is, you may be able to set the Roaming Aggresiveness (Intel supports that on Windows) but I don't think there's anything you can set on iPads. If you make sure the radios are at different power levels that might help some clients stick to the stronger radio but would defeat the purpose of enabling both on 5GHz so you may just need another AP.

To improve channel utilisation reduce the number of SSIDs if you have many and increase your minimum data rate to 24Mbps.

Re: flexible radio assignment

eglinsky2012 — Mon, 22 May 2023 17:57:41 GMT

I've also found that Apple devices are very jumpy when there are multiple radios present. Happens especially in res halls where we have an AP in every bedroom and lots of signal overlap.

I'm surprised 35 devices is overwhelming a 5 GHz radio on a 2800 at 40 MHz. What are they being used for? Streaming video? I'd be interested in what others think about using an 80 MHz channel and enabling MIMO/MU-MIMO if it's not already. (There are checkboxes in different sections of the WLAN advanced settings for "11ac MU-MIMO" and "802.11ax BSS Configuration")

The problem with the XOR radios on 2800s is they are very weak in Tx power. Notice yours is at 2 dBm compared to the dedicated radio at 18 dBm. So, those devices that are roaming between the radios constantly could be on the fringe of the XOR radio's coverage area, and even a person walking by could cause the signal to drop enough to roam. I've heard the 9100 series APs are a little better about this, but still I've been disabling dual 5 GHz mode on the 9130 and 9136 APs we have and just letting them operate in single 8x8 mode instead of dual 4x4 mode to prevent issues like this. The dual 5 GHz mode is better for very high-density, low-obstacle areas like cafeterias and lecture halls, but not normal classroom/office areas IMO.

Re: flexible radio assignment

Leo Laohoo — Mon, 22 May 2023 20:33:17 GMT

AP is a 2800.

My recommendation is to replace the AP with a different model. Particularly, do not use 2800/3800/4800/1560.

Re: flexible radio assignment

Moudar — Tue, 23 May 2023 07:52:47 GMT

Because we have many APs of these models you mentioned.

Do you mean do not use 2800/3800/4800/1560 particularly with FRA or do you mean do not use these at all!?

Re: flexible radio assignment

Moudar — Tue, 23 May 2023 07:59:51 GMT

I have only 2 SSIDs which can't be reduced (corporate and guest).

If the AP is connected to 1G switch port, the throughput according to WLC is 3MB and utilisation is 60% what does that mean? If i want to compare the throughput to the port speed is that something that we can?!

Why should throughput be improved with increased minimum data rate?

5GHz Data rates in my WLC:

Re: flexible radio assignment

Moudar — Tue, 23 May 2023 08:09:15 GMT

Can't use 80MHz because then i will have only 4 5GHz channels (Europe 36-140, 5GHz) which will generate co-channel interference!

I could do that on this specific AP, but we have already about 300MB in speed. Should doubling the channel width do any better?

Re: flexible radio assignment

Leo Laohoo — Tue, 23 May 2023 11:52:34 GMT

@Moudar wrote:

Do you mean do not use 2800/3800/4800/1560 particularly with FRA or do you mean do not use these at all!?

I mean, "do not use 2800/3800/4800/1560". Ever.

Every 2800/3800/4800/1560 have a design defect in the shape of the MARVAL WiFi chipset used. Bottom line is, the chipset would crash and traffic, randomly, gets dropped. A list of the Bug IDs (there is a long list) can be found HERE.

Re: flexible radio assignment

Moudar — Tue, 23 May 2023 13:36:42 GMT

What about Catalyst 9120 APs? Because we have been told that these are the substitute of 2800.

Do 9120 have also many bugs as the Aireonet APs?

What do you advice for substitute of 2700 serie APs (school environment) should it be 9120 or the 6e new APs 916x?

Re: flexible radio assignment

Rich R — Tue, 23 May 2023 16:05:06 GMT

I would not bother with 80MHz channels.
Increasing minimum data rates improves airtime efficiency which reduces overall channel utilisation. So if channel utilisation is high then improving it could improve throughput.
Explanation at https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-6/b_Cisco_Wireless_LAN_Controller_Configuration_Best_Practices.html#concept_C84096B4070D4377BAA73AB7B4ED05C9 and various other places on the internet. Most of those articles focus on disabling the 11b data rates but the same principle applies to the higher data rates too. In https://www.cisco.com/c/dam/en/us/td/docs/wireless/controller/technotes/8-6/Enterprise_Best_Practices_for_iOS_devices_and_Mac_computers_on_Cisco_Wireless_LAN.pdf Cisco actually recommend 12 Mbps but we've actually found 24Mbps works best in our offices and other high(ish) density environments. Remember higher data rates means smaller cells so make sure you still have adequate coverage.

9120 generally don't have the same issues that Leo is referring to on the 2800's because those problems are mostly unique to the older Wave 2 hardware.

Regarding 9120 or 916x - that's a choice you'll need to make based on cost and requirements.
As 916x is newer you'll get more life out of them and you get 6E support, environmental sensors and a few other new features so all other things being equal, if you can afford them then why not?

Re: flexible radio assignment

eglinsky2012 — Tue, 23 May 2023 17:02:06 GMT

Check out this bug, "High channel utilization on 5GHz radio with 40Mhz". It's fixed in 8.10.185.0.

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwb51757

On that note, I forgot to ask, are users experiencing slowness, or did you just notice that high utilization was reading high?

As for throughput, what you showed in the original screenshot is the current measured amount of traffic the radio is passing, not what it's capable of or what the clients would show on a speed test. You mentioned 3Mb up and down. Was that a speed test done from the client device?

Re: flexible radio assignment

Leo Laohoo — Tue, 23 May 2023 19:15:15 GMT

@Moudar wrote:

What about Catalyst 9120 APs? Because we have been told that these are the substitute of 2800.

Any AP model except 2800/3800/4800/1560. 91xx, for the time being, is immune to this issue.

@Moudar wrote:

What do you advice for substitute of 2700 serie APs (school environment) should it be 9120 or the 6e new APs 916x?

If cash is not a problem, 9136.

If cash is going to be an issue, then why throw good money for a "6e" when no one has come up with an affordable "6e" wireless client.

Re: flexible radio assignment

Moudar — Wed, 24 May 2023 06:45:18 GMT

I will create a new RF profile with 24Mbps mandatory and check if it will be better.

Why should "Noise" increase when channel utilisation increase a little bit:

Re: flexible radio assignment

Moudar — Thu, 25 May 2023 06:22:03 GMT

This is interesting. maybe it is time to upgrade.

3Mb is what WLC showed under "Throughput" When many clients were connected.

Re: flexible radio assignment

Moudar — Thu, 25 May 2023 06:29:14 GMT

24 Mb should be mandatory or disabled? On 5GHz, 2,4GHz or both? Today we run our WLC with 18Mb mandatory on 5GHz and 12Mb mandatory on 2,4GHz.

I think it's worth trying higher data rates in some crowded places with RF profile!

Re: flexible radio assignment

Rich R — Thu, 25 May 2023 15:04:45 GMT

> 24 Mb should be mandatory or disabled? On 5GHz, 2,4GHz or both?
I'm talking about 5GHz. We use 24 Mbps Mandatory and all lower data rates disabled.