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Slightly Overlapping Channels In 2.4 GHz 802.11 WLANs

In a previous post, a well known non-overlapping channel deployment configuration for 2.4 GHz 802.11 networks was outlined.

Another option is to use a four-channel deployment scheme, either 1, 4, 7, 11 or 1, 4, 8, 11. Both of these scenarios are typically called slighty overlapping channel configurations, and are suppose to increase capacity in 2.4 GHz 802.11 networks by adding another access point to the same coverage area.

Proponents of these schemes argue that the negative impact of slightly overlapping channels can be minimized by limiting access point power and using proper physical separation.

What these schemes fail to address is interference from stations that are between two adjacent access points resulting in poor wireless lan performance, and therefore defeating the purpose of this deployment scenario.

Station Interference (image from cisco.com)

Slightly Overlapping Channels In 2.4 GHz 802.11 WLANs

A spectral views of a 1, 4, 8, 11 and a 1, 6, 11 channel schemes are shown below. The peaks and valleys of the 1, 4, 8. 11 scheme are not well defined indicating interference from adjacent channels. In a high utilization environment, the slightly-overlapping scheme would result in poor performance compared to the non-overlapping scheme and should be avoided.

Slightly Overlapping – Channels 1, 4, 8, 11

Slightly Overlapping Channels In 2.4 GHz 802.11 WLANs

Non-overlapping – Channels 1, 6, 11

Slightly Overlapping Channels In 2.4 GHz 802.11 WLANs

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Filed under: WLAN Design

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