Should I enable Auto Tx Power Ctrl?


Userlevel 1
Should I enable Auto Tx Power Ctrl?
We have Enterasys 3605 in our schools; one in each classroom. How do I find out the best power level to set my radios to? I was told that our APs power level is too high, which may be causing problems with mirroring device to Apple TVs.


6 replies

Userlevel 7
Hello, Leaving that on (enabled on all ap's) should not be an issue. If you do experience any issues you could disable it via an ap multi-edit. You also may benefit from a site survey done by our Professional Services Team. If that is something you are interested in you could discuss this with your local Extreme Sales person.
Userlevel 7
For more information on what exactly are site surveys...

https://en.wikipedia.org/wiki/Wireless_site_survey

Types of Tools Used:

https://en.wikipedia.org/wiki/Comparison_of_wireless_site_survey_applications

Extreme Networks Professional Services will do the survey with Ekahau.

http://www.ekahau.com/wifidesign/ekahau-site-survey#!features-1
Userlevel 7
You'd need to unterstand how ATPC works to know whether it's the right feature for your scenario.
In short ... if APs could "see" each other on the same channel they will reduce the tx power so they don't interrupt each other = co-channel interference.

If you've i.e 3 classrooms which are kind of isolated (other zone in the building) the 3APs will hopefully chosse channel 1, 6 and 11 (NA domain, 3 channel plan).
In that case as they don't "see" another AP on the same channel all will operate at full tx power.
So you might have some clients from another classroom that connect to a AP in the neighbor room because the signal is good enough.

Because the 5GHz band has even more available channels the AP could choose from a larger range and you once again could end up with the APs running at full tx power even that isn't necessary to provide service for only a single classroom.

So you'd try it with ATPC but I'd do a site survey to see how much signal power you get in the classroom nearby do see whether that works for you.
I'd also increase the minimum basic rate for a higher performance - once again you'd need to decide according to the clients that are member in your WLAN.
I.e. if you still have 802.11b clients you can't increase the min basic rate to 12Mb as that isn't a supported 802.11b rate.

-Ron
Userlevel 2
On a similar topic, if you use ATPC, is it best to enable for a period of time and then statically set the values it comes up with or just leave it on all the time ?
Userlevel 7
Leaving ATPC to active all the time should not be a problem, Dynamic Channel Selection is something we would suggest for brief periods, then lock down the channels.
Userlevel 2
I have been testing it in a couple locations and noticed a couple AP's seem to have drifted up to the max over time which is why I asked. I walked around checking the initial results with wifiexplorer and the results were pretty good, but with the AP's drifting up I began getting too much co-channel interference. i reset them to see if it happens again, but made note of the values that worked best and will set manually if necessary.

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