The new 802.11ac WiFi will support up to eight antennas allowing devices to negotiate dedicated links, which makes multi-client networks more efficient. This means you could have one device setup to transmit to multiple machines, but not receive any data. For example, this would work really well for consumers that want to stream HD video from a single source to multiple TV's. The sub-channels will also be widened to 80/160mhz compared to the 20/40Mhz 802.11n offered. This further helps to reduce interference from other networks on different channels.
The biggest problem with 5Ghz 802.11a is range caused by a smaller wavelength when compared to 2.4Ghz WiFi. This won't be a problem with 802.11ac technology because it uses 'beamforming' techniques to map any environment to avoid inefficient signal paths. The technology will technically be capable of data speeds up to 3.47Gbps with an eight antenna AP, and four antenna client. Real world results will likely to be around 1Gbs, up 40% compared to wireless 'n' currently. The technology debuted at CES, however, the IEEE hasn't approved 802.11ac devices for use yet.
