Controller Based WLANs

How does spectrum load balancing work with and without defining the spectrum load balance domain?

Aruba Employee

Product and Software: This article applies to all Aruba controllers and ArubaOS 3.4x and later.

 

The spectrum load balancing feature helps balance the clients between different channels of the 2.4 Ghz band or 5 Ghz band, depending upon which band has the feature enabled. Balance clients between channels to maximize performance and reduce co-channel interference within the RF neighborhood. All the APs in the RF neighborhood participate in the load balancing.

 

The two methods of creating a virtual RF neighborhood are:

 

  • Automatic calculation of virtual RF neighborhood
  • Manual configuration of the RF neighborhood (spectrum load balance domain)

In the first method, the virtual RF neighborhood is created using the ARM scanning, client density updates, and neighbor exchanges.

 

ARM decides to distribute APs in different channels. All the APs then update the controller about the density of the clients associated to them. The client density updates are sent every 30 seconds by default.

The controller also uses the ARM neighbor update messages that pass between APs and the controller to determine the distribution of clients connected to the immediate neighbor of each AP. This feature also takes into account the number of APs that are visible to the clients in the RF neighborhood.

Based on these factors, the controller calculates the RF neighborhood and starts to load balance clients among all the APs that are in the RF neighborhood. APs that are far away are not a part of the virtual RF neighborhood, so the client is not load balanced to those APs.

 

In the second method, the virtual RF neighborhood is created manually by defining a domain called the spectrum load balancing domain. All the APs that are a part of spectrum load balancing domain are RF neighbors and participate in load balancing.

 

In this method, the controller ignores all the client density and neighbor exchange updates from the AP and does not calculate the RF neighborhood as described earlier.

 

Manual creation of the RF neighborhood is not very effective when ARM scanning and channel assignment is enabled, because ARM tries to assign the most noninterfering channel to AP. However, but this assignment might conflict with all the other APs that are made to be a part of the spectrum load balance domain. Therefore, this method favors static assignment of channels and power.

 

This method was used only once where the client wanted to disable ARM and channel assignment and all the required parameters such as channel, power allocation, and distance between the APs were carefully monitored and planned.

 

Note: The best practice is to:

 

  • Disable ARM scanning and channel assignment while you define the spectrum load balancing domain.
  • Manually configure channels for the AP.
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‎07-02-2014 06:11 PM
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