Channel Utilization High ( Tx High but Rx Low) Randomly

[Farkhan Khoir]

Hello. I'm a beginner in Wireless area

I manage wireless network  using WLC 9800 (version 17.3.5) and 9120 AP. We're running on SDA environtment

All connected clients are experiencing intermittent loss of connection and also slow connection when the issue happened

We didn't get signifcant log on event viewer dnac for the issue's client even with RSSI

I tried to look up the data and deal with it, but it didn't work out easily, so I'd like to ask for help. Thank you.

[JPavonM]

High utilization on the channel could be due to high load in connected clients such as sharing or downloading content.

But if this is constant all the time, and the devices are also disconnecting, this could be due to a non Wi-Fi interference source. Look for motion sensors based on radio signals to detect movement, or any other potential source of interference. For me it happened to be a faulty power unit inside a Crestron screen which was creating a constant narrow noise on channel 132 not detected as interfernce itself by APs due to its narrowness, but clearly seen in a spectrum analyzer (using Ekahau sidekick here for this). As soon as I removed that unit it all started to work fine.

To validate the beofre assumption, try to manually change the channel on the AP to another one in UNII-2c band like 140.

HTH

[Farkhan Khoir]

Thanks for your response,

the value is not constant , so is it the real traffic? 

what i confused also is why tx value is so high and rx not (any other issue on transmit an receive process)

based on this condition, should i apply QoS or other policy because i think someone had using this network excessively but i haven't any visibility for that

[Leo Laohoo]

Independently verify CU is high.  

There are several known bugs where the APs would falsely report high CU or co-channel interference. 

If this is Ch 157, is the AP near or close to a fire escape?

[Farkhan Khoir]

co-channel interference will happen if Cu high but Tx/rx low , is it correct?

nope i think the AP far enough from fire escape

[Leo Laohoo]

Verify and not make presumption. 

Does the site have motion detectors near the said AP?

[JPavonM]

Constant utilization use to lead to a non Wi-Fi interference (unless been impactede by a code defect or radio malfunction).

Could you manually assign channel 140 (or channel 48) to this AP and see the value it reports?

[Flavio Miranda]

Hi

 As you have SDA which means you have DNA Center.  You can use it to help you. Enable, if not, Intelligent Capture

https://www.cisco.com/c/en/us/products/collateral/cloud-systems-management/dna-center/guide-c07-744044.html

You can analyse the RF with that

.

[Farkhan Khoir]

Yes we have

but i think i don't have any knowledge yet about reading this spectrum

can you help us , what's the difference between red,yellow,and green colour?

and also the difference from 2 of spectrum (amplitude vs time & channel vs time)

[Rich R]

As @Leo Laohoo pointed out there have been some bugs so update software as per TAC recommended (below) in conjunction with https://www.cisco.com/c/dam/en/us/td/docs/Website/enterprise/sda_compatibility_matrix/index.html for SDA