802.11ac is a set of wireless communications specifications proposed for networking. For consumer electronics, 802.11ac will act as an evolution from 802.11g and 802.11n, widely used for wireless networking in home and corporate environments.
802.11ac products will be marketed towards users who require a lot of bandwidth and speed in their wireless networks, whether that's for gaming or streaming of high definition content from the Internet or another source on the network. It is sometimes called 5G Wi-Fi.
802.11n routers are marketed as being capable of 150Mbps with a single antenna, 300Mbps with two antennas and 450Mbps with three antennas, although realistically these speeds are rarely achieved. With 802.11 routers, the speed has been increased to 450Mbps with a single antenna, 900Mbps with two antennas and 1.3Gbps with three antennas.
Early tests of triple-antenna routers found they could achieve speeds up to 800Mbps.
There are some significant differences between 802.11n and 802.11ac. For example, Wi-Fi gear is omnidirectional, but 802.11ac hardware is capable of directional communication with devices. This beamforming results in significant reductions in interference.
802.11ac also uses the 5GHz frequency band. Most 802.11g and 802.11n hardware uses the 2.4GHz band, which is also used with a lot of other devices, such as cordless phones and baby monitors. Using the 5GHz band means that interference should be reduced significantly.
Just as with 802.11n gear, 802.11ac hardware is backwards compatible with previous wireless standard revisions.
Equipment that conforms to the 802.11ac specification is expected to ship beginning in 2012.