5508 WLC Tx Power Control(TPC)- High Density Deployment

[awatson20]

We have a multi-floor office building with a high denisty wireless deployment.  Each floor is close to 25,000 sq feet with 6 to 7 3602i AP's per floor.  There is about 1 AP per 3500 sq foot.  This is mainly for Data only, but we do some voice and will do more in the future.  My question is around the Transmit power configuration on the 5508.  RRM is setting the power levels on these access points to 5 and 6 on most all of these.  I have seen where certian client devices are not getting adequate throughput, and the RSSI is around -72 for some of these.  Would it be recommended to manually adjust the power levels on each AP, or globally set the TPC minimum power level assignment to something other than the default which is currently -10 dBm?  I typically do not modify the global TPC setting on our WLC's for indoor office envionrments, but was curious what the experts on here think as far as best practices concerning this.  Thank you.

[Scott Fella · Accepted solution]

I would set the minimum TX power to 8 or 11 and see if that helps.... The one reason AP's can lower their TX power is because they are line of sight, for example, in the hallways.  Depending on your coverage, the TX power should be tweaked. The data rates is another thing to tweak, which can also shrink your cell size so that clients roam to close access points.

Thanks,

Scott

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[Scott Fella]

You can also set the maximum TX power to maybe 17, which would be 50mW and that will also help make sure one AP isn't trying to cover everything.

Thanks,

Scott

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[awatson20]

Thanks Scott.  I appreciate your quick response.  So just that I am clear, you would adjust the minimum power level assignment from -10 to 8 or 11, and the also set the maximum from 30 to something like 17?  You are referring to the settings I have in screenshot below, correct?  Thanks again.

[Scott Fella]

Yes... those settings... you need to disable the band though, so you will have to take a down time, but not that long.

Thanks,

Scott

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[awatson20]

I had actually planned on creating an RF Profile with these settings, and then applying that profile to a specific AP Group.  Do I still have to disable the bands donig it that way?

[Scott Fella]

No, but when you move the AP's to that group, the AP's will reboot.

Thanks,

Scott

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[EvaldasOu]

Guys... could you explain, what is the purpose to have a negative power value here? (-10?)

[Scott Fella]

It's just in case you have a really high gain antenna. But I look at it as a default min to reduce the TX power to the lowest possible. Just like the max... That is outdoor power.

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[EvaldasOu]

Mhm... so the point is...

0 dBm = 1 mW

-10 dBm = 0.1 mW

Thanks!

[awatson20]

Since I am not adjusting TPC globally on the WLC, and making this change under an RF profile, when I apply the RF profile to the AP Group, will it automatically adjust at that moment?  The access points are already in this AP Group.

[msmith101]

It will start adjustments, but probably take several cycles to fully adjust.  The TPC algorythm runs every ten  minutes.  You can force it manually, but I would just let it work, after after a couple hours check the power levels, client coverage, and see if you need to make further changes to the settings.

[Scott Fella]

Takes about 30-40 minutes but DCA will have to adjust also. Typically I have DCA set at 24 hours. You can restart DCA from the CLI:

config advanced 802.11a channel global restart

config advanced 802.11b channel global restart

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[awatson20]

Thanks.  I have DCA set for 24 hours as well.

[awatson20]

Is there a recommended minimum power level assignment under TPC for the A/N Band?