In a dense office using the 2.4 GHz band, three access points sit close enough to hear one another. Which set of channels lets all three operate without their 22 MHz transmissions overlapping?
- AChannels 1, 6 and 11 Correct
- BChannels 1, 5 and 9
- CChannels 2, 7 and 12
- DChannels 3, 6 and 9
Why A is correct: In the 2.4 GHz band each 802.11 channel is 22 MHz wide and centres are spaced 5 MHz apart, so only 1, 6 and 11 are far enough apart that their occupied spectrum does not overlap.
Why B is wrong: These are evenly spaced by four channel numbers, which looks tidy, but a gap of four is only 20 MHz of centre separation, so the 22 MHz signals still bleed into each other.
Why C is wrong: Shifting the classic plan up by one keeps the spacing but pushes channel 12 outside the channels permitted in some regulatory domains, and the trio is no longer the recognised nonoverlapping set.
Why D is wrong: A three-channel gap is only 15 MHz of separation, well under the 22 MHz a channel occupies, so adjacent-channel interference results despite the neat numbering.