How many non-overlapping 40-MHz wide channels are there in the 5 GHz range?
40 MHz operation at 5 GHz involves the use of pairs of 20 MHz channels. The North American channel pairs for 40 MHz operation in the U-NII band are: 36+40, 44+48, 52+56, 60+64, 149+153, 157+161. (See Annex J of IEEE Draft 802.11n/D2.00.) These channel pairs are non-overlapping, hence there are two sets of non-overlapping channels in the U-NII low, middle and high bands.
