Automatic Channel Selection (Acs) Overview; Acs Operation - Extreme Networks Summit WM Technical Reference Manual

DRM – Dynamic Radio Management

Automatic Channel Selection (ACS) overview

ACS provides an easy way to optimize the channel arrangement based on the current situation in the
field. ACS relies on the RF environment measurements as seen by the Wireless AP, and not by a third-
party. Therefore, it is more accurate than any other methods. However, it is very important to
understand and avoid its limitations. ACS provides an optimal solution only if it is triggered on all
Wireless APs in a deployment. Triggering ACS on a single Wireless AP or on a subset of Wireless APs
provides a useful but suboptimal solution. Also, ACS only relies on the information observed at the
time it is triggered. Once a Wireless AP has selected a channel, it will remain operating on that channel
until the user changes the channel or triggers ACS.

ACS operation

ACS can be triggered by one of the following events:
A new Wireless AP registers with the Summit WM Controller and the AP Default Settings channel
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is Auto.
A user selects the Auto channel from the Wireless AP's radio configuration tabs.
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A user selects the Auto channel from the AP Multi-edit screen.
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A Wireless AP detects radar on its current operating channel and it employs ACS to select a new
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channel.
On the same Wireless AP, ACS operates independently on the two radios: when ACS is simultaneously
triggered on both radios, the result for each radio will be the same as if ACS was triggered separately
on each radio. If ACS is triggered on only one Wireless AP and one radio, that Wireless AP will scan all
available channels for that radio and then pick the best channel (according to the criteria described
below) and start operating on that channel. If ACS is triggered simultaneously on multiple Wireless
APs, the Wireless APs will synchronize and cooperate in the process of selecting channels, in order to
avoid multiple APs jumping on the same channel because it looks free.
The ACS algorithm consists of two general steps:
1 – Scanning
Scanning the RF environment in order to select the desired channel. The number of Wireless APs in the
area, channel utilization, and channel interference are some of the factors used to select the desired
channel.
2 – Channel coordination
Coordinating channel selection with other Wireless APs. The Wireless APs that are participating in ACS
will synchronize with each other over a bidding channel and then each Wireless AP will select a
channel using a bidding process. The bidding algorithm assigns the desired channel to as many
Wireless APs as possible.
You can expect the ACS process to take approximately 10-30 seconds per Wireless AP, with large
networks requiring up to 10-15 minutes for final stabilization.
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Summit WM Technical Reference Guide, Software Version 5.1