Reducing power on just some IAPs

[swestfisher]

Hi Folks,

I have one campus (three buildings) with IAP-205s. We have been receiving problems reports from one side of one building, and monitoring is showing that peak usage moves it into the high density catagory. With the controllerless system is does not look as if we can reduce power on specific IAPs to allow us to install more to handle the load. We need to maintain roaming between the low density and high density areas on this campus - what would you all recommend?

Thanks,

Steve

[cjoseph · Accepted solution]

You can statically fix the power and channel of IAPs, but you cannot reduce the power range of only some APs.  The power ranges are set for the entire cluster.

You might look to ensure that you are doing things, like running20 mhz channels for diversity, making sure the maximum transmit power is not more than any of the devices you are supporting, and that the difference between your ARM max transmit power and your ARM min transmit power is no more than 6.  And of course, use broadcast filtering on all of your SSIDs.

[swestfisher]

Could you elaborate on "making sure the maximum transmit power is not more than any of the devices you are supporting"? I'm not sure I understand what you mean there.

Thanks,

Steve

[cjoseph]

Please see the "WLAN Optimization" section of the 802.11ac Validated Reference Design Guide here:  http://community.arubanetworks.com/t5/Validated-Reference-Design/Aruba-802-11ac-Networks/ta-p/242637 for more context.

[swestfisher]

I've read the section but still don't understand what you mean by making sure transmist power is not more than devices we are supporting, I'm not sure I understand what IAP transmit power has to do with the user devices.

Also, most of the option in that section are not available - or at least called something else in the IAP interface I think.

Thanks,

Steve

[cjoseph]

IAPs have an ARM minimum and maximum transmit power that you configure.  That is the range of transmit power that APs will be allowed to have:

http://www.arubanetworks.com/techdocs/Instant_41_WebHelp/InstantWebHelp.htm#UG_files/ARM/Configuring_ARM-Features.htm?Highlight=arm minimum

You should make the difference between the minimum and maximum no more than 6 so that the difference between the highest possible AP transmit power and lowest possible transmit power is only 6.  This is so that the performance of clients is not uneven based on which access points they connect to.

The maximum transmit power of the access points should not surpass the transmit power of typical devices.  If an access point transmit power is significantly higher than the transmit power of the client that attaches to it, the client will think it can communicate with an access point that can no longer hear it well, creating a "sticky client" issue.  This will create application performance issues on the client, as a result.  Typically you can start with a minimum of 12 and a maximum of 18.  A much more technical explanation of this is here:  http://www.greatwhitewifi.com/2016/05/14/power-matching-transmit-power-or-eirp/

The document I referred you to does make references specifically about controller-based parameters, but the ARM minimum and ARM maximum transmit power is the same parameter between controller-based and Instant Cluster-based deployments.

[swestfisher]

Ok, now I get it - I can be a bit thick at times :-)

I hadn't seen the link about client power and hadn't thought about it that way, that could be the answer to problems at another site.

Thanks,

Steve