You’ve started hearing the term 802.11ac in the news, or have seen new laptops shipping with 802.11ac WiFi. 802.11ac is the newest WiFi wireless networking protocol, and here’s what you need to know:

Fifth Generation WiFi

802.11ac builds upon the success of 802.11n, which is now the predominant WiFi standard in the market. As the fifth generation WiFi standard, 802.11ac is a faster and more scalable version of 802.11n. It’s designed to counter the explosion of mobile devices and high-bandwidth mobile real-time applications like video and voice by delivering higher levels of WiFi that are on par with Gigabit Ethernet.

In essence, 802.ac provides a very high data rate by using a much wider spectrum; it’s twice as fast as 802.11n and three streams will deliver speeds up to 1.2 Gbps.

How Fast is 802.11ac?

The most important question is just how fast is WiFi 802.11ac? As with any WiFi standard, it’s important to realize there’s a big difference between the maximum theoretical speeds achieved in a lab and the speeds you’ll actually see in your home (where there are obstacles and other things to weaken the WiFi signal).

The theoretical maximum 802.11ac speed is eight 160MHz 256-QAM channels which are each capable of 866.7 Mbps. So, that means the grand theoretical total nears 7 Gbps! However, in the real world, you probably won’t be using eight channels (more like two or three), giving you a real-world maximum between 1.7- 2.5 Gbps. Compare that with the 600 Mbps maximum theoretical speed for 802.11n. Of course, still keep in mind that 2.5 Gbps is a real world maximum speed – your maximum speed will be dependent on your home environment.

How Does 802.11ac Work?

Existing 802.11 Wi-Fi standards operate either in the 2.4 GHz band (802.11b and 802.11g), the 5 GHz band (802.11a), or both 2.4 and 5 GHz (802.11n). 802.11ac operates strictly in the 5 GHz. The 5 GHz band is typically cleaner, without the wireless interference common at 2.4 GHz, including older Bluetooth devices, cordless phones, and microwave ovens. 802.11ac is backwards compatible with other 802.11 technologies (i.e. 802.11n) that operate in the 5 GHz band. But keep in mind that if you want your 802.11ac router to support your older 2.4 GHz client devices, you’ll need to find a dual-band 2.4/5 GHz router.

On a technical level, key enhancements supported by 802.11ac WiFi include:

  • Wider channels: Increased from the maximum of 40 MHz in 802.11n to 80 MHz and even 160 MHz (optional)
  • Improved modulation resulting in increased bandwidth/capacity
  • Increased number of spatial streams: 802.11n stopped at four spatial streams; 802.11ac goes up to 8 spatial streams for a speed increase of 100%
  • Multiuser MIMO (to be available in the second phase of 802.11ac): MU-MIMO allows an access point to send multiple frames to multiple clients at the same time over the same frequency spectrum (much like a wireless switch).
  • Beamforming to increase the effective range/coverage: this is going to be critical, since 802.11ac, by nature of it using 5 GHz, has a shorter range than 2.4 GHz standards.

Is 802.11ac Ready Now?

Although there are already 802.11ac routers, laptops, and adapter cards on the market today, the 802.11ac standard has not been ratified by the WiFi Alliance yet. This means that buyers can’t be assured that the 802.11ac products they buy today will work together, or be able to work with 802.11ac products released tomorrow.

At present, the working group responsible for 802.11ac is expected to finish its work in November 2013, with a planned ratification of the standard around February 2014. While the standard is still a draft, the WiFi Alliance will begin a certification program based on the 802.11ac draft standard.

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