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ePMP Tools: Automatic Channel Selection and 2.4/5 GHz Operation

Moderator

ePMP Tools: Automatic Channel Selection and 2.4/5 GHz Operation

ACS.pngOverview

Use the Tools -> Automatic Channel Selection page to use the Automatic Channel Selection feature to allow the AP to choose the best channel possible under the current RF environment. This feature is not available when the AP is in ePTP Master mode.  

 

When enabled, ACS scans the entire band (governed by the Country setting) and chooses a channel with the lowest channel occupancy i.e. lowest interference level.

 

Re-running ACS

To initiate the ACS feature (once enabled), the radio has to be rebooted or the feature may be manually triggered using Tools -> Automatic Channel Selection.

 

How ACS selects a channel

When ACS is running, the radio measures the occupancy level of the channel (measured in terms of an internal interference metric) and uses an algorithm to make a decision to choose the best channel within the band. The channel chosen is not based just on the occupancy level channel but also the occupancy level of adjacent channels.

 

In the 5 GHz band, ACS considers the occupancy level of 9 total channels - 4 lower-adjacent channels, the channel under inspection, and the 4 upper-adjacent channels.  

 

The 2.4 GHz band is narrower than the 5 GHz band, and in the 2.4 GHz band ACS considers the occupancy level of 3 total channels - 1 lower-adjacent channel, the channel under inspection, and 1 upper-adjacent channel.  

 

If ACS is inpecting a channel at the edge of a the band (2.4 GHz or 5 GHz), ACS only considers adjacent channels up to the edge of the band.  ACS takes a weighted average of adjacent channel occupancy, with weights decreasing the further the adjacent channel is from the center frequency under inspection.

 

Note

The channel bandwidth configured prior to enabling and running ACS will be used to automatically select a channel. For example: If the operator manually configured a channel bandwidth of 20MHz, ACS will scan and choose a channel of 20MHz wide channel. To switch ACS to 40MHz or other channel bandwidth, the operator should disable ACS, manually configure 40MHz or desired channel bandwidth on the radio, then enable and run ACS. 

 

Additional Automatic Channel Selection parameters

Minimum Dwell Time

Configure the minimum time in milliseconds for which the radio needs to scan a channel to measure channel occupancy or interference levels. Default is 200 ms.

Maximum Dwell Time

Configure the maximum time in milliseconds for which the radio needs to scan a channel to measure channel occupancy or interference levels. Default is 300 ms.

Results

Click this button to download the most recent ACS results in .csv format.