401 495FREQUENCY (GHZ)FREQUENCY (GHZ)

2.401 2.495Frequency (GHz)Spread Spectrum Technology 143

Of these 14 channels, mathematically there are only 3 adjacent non-overlapping chan-

nels, with the exception of channel 14. Per the IEEE 802.11-2007 standard, “Channel 14

shall be designated specifically for operation in Japan.” There are 3 MHz of separation

where the radio frequency of one channel ends and the next adjacent non-overlapping chan-

nel begins. For example, channel 1 and channel 6 are adjacent non-overlapping channels.

Channel 1 ends at 2.423 GHz and channel 6 begins at 2.426 GHz. Mathematically this is

a separation of 3 MHz. This means that three access points can be co-located in the same

physical space without overlapping channel interference. However, there is still theoreti-

cally a small amount of overlapping RF or harmonics between these two channels. This

small level of overlap is not large enough to cause any real interference issues. Figure 5.9

illustrates 3 of the first 14 channels that do not overlap in the 2.4 GHz ISM band.

f i g u r e 5 . 9 3 Non-overlapping channels possible in the 2.4 GHz ISM bandPower (mW)Channels 1, 6, and 11 do not overlapChannel 1 Channel 6 Channel 11