IEEE 802.11ac supports 40 MHz, 80 MHz,
and 160 MHz channel bandwidth compared to
only 20 MHz and 40 MHz supported by 802.11n.
The 160 MHz channel bandwidth is composed of
two 80 MHz channels that may or may not be
contiguous. The 80 MHz and 40 MHz channels
are composed of two contiguous 40 MHz and 20
MHz channels, respectively. The support of 40
MHz and 80 MHz channel bandwidth is mandatory
while support of 160 MHz and 80 + 80
MHz is optional.