AP DCA question

[IT Services]

Good Afternoon,

I am hoping someone has a quick answer on how to resolve or better understand what oculd be going on with our DCA configuration and an Flex Connect AP.

Currently we have 3 - 3602i's configured in flex connect mode. These AP's cover a 3600-4000 sq. ft. area.

I have worked on eliminating some lower data rates and messed with Power Levels to better tune the RF environment for this site.

I checked the Channel assignments giving for the 2.4ghz network and 2 out of the 3 AP's are both globally set to channel 11. On AP-1 channel 6 has little to no interference or noise detected, so i dont know why the AP hasn't assigned it's self to that channel.

Anything I can do to invoke the AP to recalculate and perform DCA if need be? I dont want to interrupt our other AP's running on this controller.

Thoughts?

[Scott Fella · Accepted solution]

Well.... RRM requires at least 3 ap's heard at a certain level.  Since your AP's are pretty spread apart, this is what I would expect.  By default, an AP will assign itself channel's 11 or 1, until you have more AP's or they are in a higher density location, then RRM would assign an AP on channel 6.  If you have 3 AP's, you either can assign the channels yourself or just leave it up to the WLC.

Thanks,

Scott

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[Scott Fella]

Here is from a doc:

Q. I have set the Radio Resource Management (RRM) to the default settings on my WLC. However, I cannot find my RRM to automatically adjust the channel and power levels. Why?

A. RRM possibly does not work for any of these reasons

• The RRM works only if an AP hears RF signals from at least 3 nearby APs, with a third neighbor that transmits a signal strength greater than -65dbm. If any of these condition fails, the RRM does not work.
• The auto RRM feature includes channel adjustment, power adjustment, and coverage hole detection. These features do not work if they are either disabled or the method of assignment is chosen as manual.

While a fresh AP boots up, it initially keeps power at the default value of 1 (highest). When it sees 3 or more APs with power levels greater than -65 dBm (in the same RF-Mobility-Domain and same channel), it attempts RRM first (change channels). If not successful because the channels are manually fixed or there are more APs than channels available, the AP drops its power level.

Refer to Radio Resource Management: Concepts for more information on how RRM works.

Thanks,

Scott

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[IT Services]

Scott Fella wrote:
Well.... RRM requires at least 3 ap's heard at a certain level.  Since your AP's are pretty spread apart, this is what I would expect.  By default, an AP will assign itself channel's 11 or 1, until you have more AP's or they are in a higher density location, then RRM would assign an AP on channel 6.  If you have 3 AP's, you either can assign the channels yourself or just leave it up to the WLC.
Thanks, 

Scott 

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DAMN!

I was hoping that the DCA was not depending on the minimum of 4 AP's on the same mobility domain. So it looks like I'm in the same boat i was in with the Power levels.

Thanks for the feedback Scott. Much appreciated.

[Scott Fella]

No problem... like I said, you can manually set the channels since you only have 3 and also crank up the TX if you wanted.  Not like they are going to interfere with each other being that far apart.

Thanks,

Scott

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[IT Services]

Scott Fella wrote:
No problem... like I said, you can manually set the channels since you only have 3 and also crank up the TX if you wanted.  Not like they are going to interfere with each other being that far apart.
Thanks, 

Scott 

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I may have mis-stated. The AP's total cover 3600-4000 sq. ft of area so. So the area is not very large. I want to essentially decrease the cell sizes and provide a nicer roaming experience. I still have to look to 802.11r and 802.11k but I wanted to tune in the RF environment first.

[Scott Fella]

Okay... well you have options here.  tuning isn't a big deal unless you do have interference.  As long as their is coverage, you should be fine.  You can always disable the lower data rates if not required by devices, which helps with roaming and clients not sticking and also lowering the TX power.  802.11r works if devices support it, so be careful if you enable that and have devices that don't support it as they will not connect.

Thanks,

Scott

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[IT Services]

Scott,

Does CCX client roaming parameters fall under the same requirements that RRM does?

I am curious to tweak these settings to better assist in roaming for a certain environment.

Also, if it does work without meeting a minimum of 3 neighboring AP's, is it possible to configure these settings per AP group or Flex Group? The reason I ask is because we have numerous wireless enviornments running on this controller and i cannot gurantee that the RF design is suited for thightening the roaming parameters.

Thoughts?

[Scott Fella]

To be honest, I don't think enabling that will help. The best thing that can help in your environment is to use RF Profiles within AP Groups which will allow you to tweak each AP Group environment. You need to really understand the RF and if you have enough RF coverage, are the AP's located in a good location for when clients need to roam, is there interference, etc.

Look at it this way.... Your AP's are your layer 1, if the layer one is bad, nothing you can do in the WLC can fix that. Have you had a site survey performed and a post site survey or validation to see your existing coverage?

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[IT Services]

Scott Fella wrote:
To be honest, I don't think enabling that will help. The best thing that can help in your environment is to use RF Profiles within AP Groups which will allow you to tweak each AP Group environment. You need to really understand the RF and if you have enough RF coverage, are the AP's located in a good location for when clients need to roam, is there interference, etc.

Look at it this way.... Your AP's are your layer 1, if the layer one is bad, nothing you can do in the WLC can fix that. Have you had a site survey performed and a post site survey or validation to see your existing coverage?

Sent from Cisco Technical Support iPhone App

Ha. Site Survey what a concept

Anyway. Yeah i just thought since this one particular and other environments in high traffic\high interference areas we would benefit from tighter CCX client roaming feature settings. I noticed even with the CCX clients that we are not able to roam to a certain AP. How ever that AP see's the most noise and interference based on the reports to the controller.

[IT Services]

Scott,

One more question. If a set of AP's are CAPWAP attached but doesnt meet the requirements to run RRM. Do they still perform DFS? If they dont is it in our best interest to try to use non-DFS based channels on the 5ghz spectrum?

[Scott Fella]

They will still be affected by radar, so yes, DFS will still run.  Only if you are affected by radar, then move away from the DFS channels to avoid the AP from disassociating clients.

Thanks,

Scott

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[IT Services]

Let me make sure I understand this correctly.

If the APs dont perform RRM then they dont perform DCA correct? But they still perform DFS if they were configured for global configuration and controller controlled?

[Scott Fella]

DFS is enabled by regulation.... has nothing to do with RRM.  RRM requires minimum of 3 AP's for DCA or TPC changes.

Thanks,

Scott

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[IT Services]

Thanks again Scott,

I am sure I can find my next question in documentation but your soo quick lol.

How often does the AP scan for radar signal when using a DFS channel or using the controller global configuration?