Co Channel interference 5Gh

[craiglebutt]

I'm getting a lot of CCI on 5Ghz, carried out survey using Ekahau Sidekick.

Alot of this are from homes and buisness around our site and other buildings, seen at -80DB

5Ghz is currently set to 40Mhz, so we are looking at moving it back to 20Mhz,  In the UK, we can't use all the 9 channels, only becosue of 3 20mhz channels used for Radar, seems to be hard coded, even TAC couldn't release it.

The reason is due to being a very large hospital with 1000's of Endpoints connecting daily.

When I make the change in RRM, the APs wont take affect till after a reboot or forcing each one to 20Mhz, My question is, is there a faster way of carrying this out?

This is on a 8510, latest code, so can't tie in with an update.

[Leo Laohoo]

The 5.0 Ghz radio will need to be disabled first before changing the width to 20 Mhz.  I would strongly recommend this is done using CLI to make the interruption faster.

config 802.11a disable network
y
config advanced 802.11a channel dca chan-width 20
config 802.11a enable network

[craiglebutt]

Thanks for the cli, was going to try try on test wlc.

But issue also the APs will need to be rebooted, work on 20Mhz.  So I noticed that is a patch update out for our 5520s so I'll tye it in with that, unless we get the new WLCs.

[Rich R]

Good idea to drop back to 20 MHz in that environment *but* "In the UK, we can't use all the 9 channels, only because of 3 20mhz channels used for Radar, seems to be hard coded, even TAC couldn't release it."?
We don't seem to have any trouble configuring 9 x 40 MHz channels in UK on 8.5.182.0 on 8510.
Which channels were you trying to configure? 
What error message were you getting? 
Which channels couldn't you configure?
What models of AP?
There are a few interdependent RF settings which can affect which channels you can assign in the RF profile and some of the error messages can be quite confusing and others literally tell you what is wrong that needs changing before you can assign the channel.

[craiglebutt]

8510 has a mixture of 3500, 2600 and 3700, but also have the same issue on 5520 are all 2800

Channels 120,124,128

Clients will not connect if I manually force the AP over, 

Summary from TAC

Case summary: basically I investigate those channels in your country, I found some interesting things related to the subject. One of them was you cannot assign the Channel manually on Europe as per ETSI compliance. If the RRM is not assigning the channel, it is in use. So that’s the main reason for the issue.

chees

[Rich R]

You should be able to assign: 36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140 without any problem.  Might want to leave 140 out if you want 40 MHz channels because that results in a 20MHz channel.
I can see we have APs using (116,120) and (128,124) so they definitely work.
I think you've got one of those 1st line TAC engineers who knows less about WiFi than we do!

> "One of them was you cannot assign the Channel manually on Europe as per ETSI compliance. If the RRM is not assigning the channel, it is in use."

So I think he's referring to DFS but clearly doesn't know enough to say so!
Draytek has a nice summary here https://draytek.co.uk/information/blog/ofcom-relax-the-rules-on-the-5ghz-band

So like with any DFS channel if the AP detects "radar" then it won't use the channel.  Now accuracy of detection of radar is variable.  And remember there are many things that might use radar that could trigger this detection like motion sensors used for security systems, electric doors and automatic lighting, for example.  Sometimes even a speed camera (like GATSO) or red-light camera using radar outside the building can trigger radar detection.  The wider your channel width the higher the probability of false radar detection by the AP because the APs sometimes confuse 80/160 MHz bonded channels with radar.  There've been a number of bug fixes for reducing false positives.

> This is on a 8510, latest code, so can't tie in with an update.
Are you sure you're already on 8.5.182.7?  This is needed to resolve the expired AP code cert download issue and it also contains security vulnerability fixes.  (see the link below)

[Arshad Safrulla]

I can see that you are taking the correct steps to address the issue. Moving to 20MHz is the best choice and way forward for you. I would not consider any DFS channels if any critical services are dependent on that such as Voip or any life saving appliances. After a change to RRM, it is highly recommended (I consider to be mandatory) that you do a RRM restart.

config 802.11a channel global restart

config 802.11b channel global restart

UK does allow UNII3 channels, it is basically blocked by Cisco. 

Statement: Improving spectrum access for Wi-Fi – Spectrum use in the 5 GHz and 6 GHz bands (ofcom.org.uk)

TAC response - "the support for -E regulatory domain APs to use UNII-3 channels on upcoming versions 17.9.2/17.10.1  would not apply to all countries, just very specific cases" Since Meraki allowed UNII3 in UK very recently I expect it to be added in the latest codes, but not sure whether this will apply to 8510 which is supported till 8.5.X codes only.