802.11ac – Future of Wi-Fi Technology............

802.11ac is a supercharged version of 802.11n. 802.11ac is dozens of times faster, and delivers speeds ranging from 433 Mbps (megabits per second) up to several gigabits per second. To achieve that kind of throughput, 802.11ac works exclusively in the 5GHz band, uses plenty of bandwidth (80 or 160MHz), operates in up to eight spatial streams (MIMO), and employs a kind of technology called beamforming that sends signal directly to client devices.

If you’re currently using an 802.11n router — or an even older 802.11b/g model, like the perennial favorite Linksys WRT54G — and are thinking of upgrading to 802.11ac, here’s what you need to know.

How 802.11ac works

 

Years ago, 802.11n introduced some exciting technologies that brought massive speed boosts over 802.11b and g. 802.11ac does something similar compared with 802.11n. For example, 802.11n supported four spatial streams (4×4 MIMO) and a channel width of 40MHz. But 802.11ac can utilize eight spatial streams and has channels up to 80MHz wide — which can then be combined to make 160MHz channels. Even if everything else remained the same (and it doesn’t), this means 802.11ac has 8x160MHz of spectral bandwidth to play with versus 4x40MHz — a huge difference that allows 802.11ac to squeeze vast amounts of data across the airwaves.

To boost throughput further, 802.11ac also introduces 256-QAM modulation (up from 64-QAM in 802.11n), which squeezes 256 different signals over the same frequency by shifting and twisting each into a slightly different phase. In theory, that quadruples the spectral efficiency of 802.11ac over 802.11n. Spectral efficiency measures how well a given wireless protocol or multiplexing technique uses the bandwidth available to it. In the 5GHz band, where channels are fairly wide (20MHz+), spectral efficiency isn’t so important. In cellular bands, though, channels are often only 5MHz wide, which makes spectral efficiency very important.

802.11ac also introduces standardized beamforming (802.11n had it, but it wasn’t standardized, which made interoperability an issue). Beamforming transmits radio signals in such a way that they’re directed at a specific device. This can increase overall throughput and make it more consistent, as well as reduce power consumption. Beamforming can be done with smart antennae that physically move to track a device, or by modulating the amplitude and phase of the signals so that they destructively interfere with each other, leaving just a narrow, interference-free beam. The older 802.11n uses this second method, which can be implemented by both routers and mobile devices.

Finally, 802.11ac, like 802.11 versions before it, is fully backwards compatible — so you can buy an 802.11ac router today, and it should work just fine with your older 802.11n and 802.11g Wi-Fi devices.