9166I reducing 5GHz transmit power - AP Power save

[ashmead123]

We have 9800-40 controllers running 17.9.3 with around 500 9166I-ROW APs. The RF profile reduces the channels to UNII 1,2 and 3 (UNII 2ext is disabled along with channels 144 and 165).

I have noticed that some of the APs in quieter areas of the deployment and using the UNII 3 channels have reduced the 5GHz transmit power. The controller shows the 5GHz radio power at 17dBm, however, an Ekahau sidekick registers only -85dBm when in close proximity.

The 2.4GHz radio is all fine and can be seen with good signal.

My thoughts are that this is the AP Power save mode as no clients are connected. However, no power profiles have been configured. Is power save mode enabled by default?

The 6GHz radio is enabled on all the APs, this seems to be the opposite power level to the 5GHz. When 5GHz is low 6GHz is high and vice versa.

Any help on this is much appreciated..

[marce1000]

 - Have a checkup of the  9800-40 controller's configuration(s) with the CLI command show tech wireless ; feed the output into
                                         https://cway.cisco.com/wireless-config-analyzer/

   Besides the basic controller report ,examine the other section(s) of the report(s) too  where you may get additional info's concerning RF behavior , 

 M.

[ashmead123]

Thanks Marce, I'll give the config analyser a try

[Rasika Nayanajith]

Hi Ashley,

"The controller shows the 5GHz radio power at 17dBm, however, an Ekahau sidekick registers only -85dBm when in close proximity."

There appears to be an issue,I'd recommend verifying if this behavior is consistent among all APs without connected clients. I hope radios are in client service mode.

"My thoughts are that this is the AP Power save mode as no clients are connected. However, no power profiles have been configured. Is power save mode enabled by default?"
Did you try to connect a client on to 5GHz & check if that make any difference?

"The 6GHz radio is enabled on all the APs, this seems to be the opposite power level to the 5GHz. When 5GHz is low 6GHz is high and vice versa."

Typically increased power on 6GHz (compare to 5GHz) to compensate higher FSPL on 6GHz. I would compare below CLI output

show ap dot11 6ghz summary

show ap dot11 5ghz summary

HTH
Rasika
*** Pls rate all useful responses ***

[ashmead123]

Hi Rasika, thanks for your responses.

'There appears to be an issue,I'd recommend verifying if this behavior is consistent among all APs without connected clients. I hope radios are in client service mode.'

I surveyed a sample area of the site and found that several APs exhibited the same behavior. Unfortunately many APs are located in corridors and will be able to see at least 2 neighbours at high power. It was in these areas that the issue was present on a single AP in that area. I will check the client service mode option.

'Did you try to connect a client on to 5GHz & check if that make any difference?'

Yes I checked this and the client would not connect, however, as you know it is very difficult to get a client to connect to a specific AP when there are neighboring APs in the area.

'Typically increased power on 6GHz (compare to 5GHz) to compensate higher FSPL on 6GHz. I would compare below CLI output'

Thanks will check this.

Thanks again for your input Rasika. Hope to see you in Prague!

[ashmead123 · Accepted solution]

I have found that this issue is related to the following bug:

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwf85025

Symptom: 5ghz AP signal decreases a lot after a channel change

Conditions: Observed in 9166-ROW local mode AP running 17.9.3 with country code GB after channel change to DFS channel

Workaround: Reload AP or change channel manually