ZyXEL Communications NXC5200 User Manual page 175

Chapter 10 Wireless
In the 2.4 GHz spectrum, each channel from 1 to 13 is broken up into discrete 22
MHz segments that are spaced 5 MHz apart. Channel 1 is centered on 2.412 GHz
while channel 13 is centered on 2.472 GHz.
Figure 71 An Example Three-Channel Deployment
Three channels are situated in such a way as to create almost no interefence 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 72 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 73 An Alternative Four-Channel Deployment
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NXC5200 User's Guide