High Channel Utilization

[hs08]

What can we do if we have high cnahlle utilization? 

Below AP operate under channel 6

In this floor i have 5 APs and other 4 APs not use channel 6

[Leo Laohoo]

2.4 Ghz only has three channels to play with.  And every wireless client and wireless AP is competing for those meager air times.  

[Saikat Nandy]

2.4Ghz is prone to interference and noise and there is no way you can get rid of this issue. You can slightly lower it (by removing external interferer/noise sources or planning the channel, if you have good idea about the RF environment) but you can not eliminate it completely. As @Leo Laohoo mentioned, 2.4Ghz is having only 3 usable channels. So there is co-channel interference in 2.4Ghz but adjacent channel interference is also there. Most of the regular interferer and noise operate in the 2.4Ghz like bluetooth, microwave etc. From your shared 'show run' I can see quite a few interferer/Persistent Interference Devices being reported. So try not to use 2.4Ghz as much as possible - unless you have some funky devices which likes only 2.4Ghz.  

[Scott Fella]

Just to add, this goes back to troubleshooting onsite with specialized tools.  For many years, folks have seen this and have had to troubleshoot and learn from it.  Tools like NetAlly for example can help determine what is in the air and affecting your RF.  Same thing with Ekahau and other software for surveying and troubleshooting.  You are also talking about 2.4GHz, which by now, is way over utilized due to the channels available.  That is why folks are trying to get devices on 5GHz and now 6gHz.  I wouldn't worry about it, since you have 0 clients connected to that ap and they are connected to 5GHz, which will be better for the end user. Now if you know you have 2.4GHz only clients or clients that prefer 2.4GHz, then that is more work on your part to tweak the network so that you can have a usable 2.4GHz if that band is really needed.

[Leo Laohoo]

In relations to high CU in 2.4 Ghz, Windows-based laptops often come with "default" or factory-installed wireless NIC drivers and (some) network administrators refuse to update them because they do not have the know-how to do a fleet-wide update.   This fact is highly important because the factory-installed wireless NIC drivers have very limited features and functionalities.  One of those is roaming and prioritizing 5.0 Ghz (over 2.4 Ghz).  

Brand new laptops will join 2.4 Ghz regardless how bad 2.4 Ghz spectrum is.  That is a known fact (for more than 10 years) -- Update the drivers and improvements will happen.  

[Haydn Andrews]

Tune the 2.4 to remove all APs doing it
Better suggestion is to move to 5GHz only

[Leo Laohoo]

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@hs08 wrote:

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Wait a second ... The AP is a 3800 with a Regulatory Domain of "-F" (Indonesia).  40 Mhz channel width.  The WLC is probably AireOS.  

Let me guess ... WiFi issue with the 5.0 Ghz?  

If I piece together the other thread (5Ghz DCA) then I'd say there is no available channel left. 

UNII-3 has four channels.  Someone has configured 40 Mhz channel width for 5.0 Ghz.  So this brings the allowable "channels" to use from four to just two.  

I would strongly suggest just using 20 Mhz channel width to free up more channel options.

[sidshas03]

Hey,

From the screenshot you shared, I can see the 2.4 GHz channel utilization is showing 86%, which is quite high. Since it’s operating on channel 6 and there are no clients connected, most likely the high utilization is due to interference or noise, not actual traffic.

Now in 2.4 GHz, we only have three non-overlapping channels – 1, 6, and 11. If multiple APs are using channel 6 in the same area or nearby floors, they will start interfering with each other (co-channel interference). You mentioned there are 5 APs on that floor and other 4 are not on channel 6, so that’s good. Still, it’s possible that something external is causing interference – like Bluetooth devices, cordless phones, or even microwave ovens.

One more thing – I noticed the transmit power on 2.4 GHz is set to 20 dBm. That’s quite strong. You can try reducing it a bit, so the coverage overlaps less with nearby APs. Also, if most of your clients support 5 GHz, then you can even consider disabling 2.4 GHz radio on some APs to reduce unnecessary interference. If you are using controller-based deployment, make sure Dynamic Channel Assignment (DCA) is enabled – that can help the controller auto-adjust channels and power levels depending on conditions. And if your APs support CleanAir, you can check if it's detecting any non-Wi-Fi interference sources. Try these steps and monitor again. If utilization is still high, we might need to look at spectrum analysis or interference source tracing.