RRM Question - how many neighbours?

Answered Question
Mar 12th, 2009

Does anyone know how many neighbors an AP need to be able to hear for RRM to manage its power output?

I have installed a few networks of LWAPP AP's (4.x & 5.x) and they just seem to sit there blasting out at full power.

The sites have usually been surveyed for Cisco LWAPP deployments. The channel configuration seems to be taken care of OK (1,6,11), but the power is just full volume.

I wondered if perhaps the issue is not just proximity to an AP neighbor, but perhaps the number of neighbors an AP can hear?

Any clarificatrion would be appreciated.

Thanks

Nigel.

I have this problem too.
0 votes
Correct Answer by dennischolmes about 7 years 8 months ago

a good rule of thumb is -70 between all APs. This allows for most clients to be -65 or better. "Each AP must hear at least 2 other APs at -75 or better for auto RF to work properly" was the old way of assigning proper LWAPP density.

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Correct Answer
dennischolmes Thu, 03/12/2009 - 13:10

a good rule of thumb is -70 between all APs. This allows for most clients to be -65 or better. "Each AP must hear at least 2 other APs at -75 or better for auto RF to work properly" was the old way of assigning proper LWAPP density.

Lucas Phelps Fri, 03/13/2009 - 07:14

Rob,

Great document. However, it does not address H-REAP situations.

From the Cisco Enterprise Mobility 4.1 Design Guide:

While in connected mode, all Radio resource Management (RRM) functionality is fundamentally available. However, because typical H-REAP deployments comprise a smaller number of APs, RRM

functionality may not be operational at a branch location. For example, in order for transmit power control (TPC) to work, there must be a minimum of four H-REAPs in proximity to each other. Without

TPC, other features such as coverage hole protection will be unavailable. For more information regarding Cisco Auto RF functionality, see Chapter 3, “WLAN Radio Frequency Design Considerations.”

So for your H-REAP offices, you'll need 4 for the algorithms to work correctly.

Link to the design guide: http://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob41dg/emob41dg-wrapper.html

-Luke

rob.huffman Fri, 03/13/2009 - 09:38

Hey Luke,

Very good stuff! +5 points for your great additions here.

Cheers!

Rob

Nigel Bowden Fri, 03/13/2009 - 14:56

Thanks for all of the great info.

Looking through a number of docs, it seems that each AP needs to be able to hear 3 other AP's for RRM to work.

This probably explains many of the issues I have seen with AP's sat transmitting at full power.

Thanks again guys.

Nigel.

George Stefanick Mon, 03/16/2009 - 17:47

Ive found that most surveys conducted at or above 50mW TX power will not properly work with RRM.

Survey conducted at 25mW / 20% cell overlap work much better. You dont see the 100mW swings up and down.

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