ZyXEL Communications ZyWall USG20-VPN User Manual page 140

Chapter 8 Wireless
Figure 115 An Example Three-Channel Deployment
Three channels are situated in such a way as to create almost no interference with one another if
used exclusively: 1, 6 and 11. When an AP broadcasts on any of these three channels, it should not
interfere with neighboring APs as long as they are also limited to same trio.
Figure 116 An Example Four-Channel Deployment
However, some regions require the use of other channels and often use a safety scheme with the
following four channels: 1, 4, 7 and 11. While they are situated sufficiently close to both each other
and the three so-called "safe" channels (1,6 and 11) that interference becomes inevitable, the
severity of it is dependent upon other factors: proximity to the affected AP, signal strength, activity,
and so on.
Finally, there is an alternative four channel scheme for ETSI, consisting of channels 1, 5, 9, 13. This
offers significantly less overlap that the other one.
Figure 117 An Alternative Four-Channel Deployment
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