802.11ac series intro: Moving into the fast lane
By Matthew Gast
No doubt about it, 802.11ac is exciting. Here at Aerohive, we like anything that increases Wi-Fi speeds, so there’s nothing more exciting going on in Wi-Fi. As a result of all the questions I’m getting on this emerging technology, I’ve decided to write a series of blog posts here to answer questions I’m frequently asked.
Perhaps most importantly in light of the success of Wi-Fi over the past decade, I’ll start off with the backward compatibility question. Upgrading to 802.11ac increases capacity and therefore decreases network load. In the 802.11 radio link, the load is measured in demand for airtime, not in terms of demand for the transfer of bits. By increasing the data rate, it’s possible to transfer more data while decreasing the load on the radio network. Decreased loads are like traffic-free roads – they are good for everybody that uses the road.
Although a bit of 802.11ac makes every network better, the real purpose of the upgrade is to provide speed. What everybody first notices about 802.11ac is that it’s fast. Really fast. Just like 802.11n, the newer specification introduces several techniques to improve end-user speeds. In that post, I plan to describe the protocol features that create higher speeds, and tell you what it means for building the hardware that you use to build your networks.
One of the major techniques for increasing speed in both 802.11n and now 802.11ac is wider channels. As an industry, we learned a great deal from the 40 MHz channels in 802.11n, and those lessons drove some neat features in 802.11ac to share channels. With 80 MHz channels, some overlap is inevitable. 802.11ac has some cool features to share wide channels on demand and to signal the bandwidth needed to transmit a frame. These features are not talked about much, but have the potential to really drive throughput increases that your network needs to support.
Wider channels are important to increasing speed, and the available radio spectrum drives network capacity. The recent announcement by the FCC chairman of new spectrum was a shock wave that really helped Wi-Fi. I wrote about it recently, and as I think about it more there are several implications for Wi-Fi in general and 802.11ac in particular. Other spectrum-related blogs I've recently written include NTIA weighs in on FCC's 195 MHz spectrum announcement and Why we lost the weather radar channels.
Next up, I’ll tackle two commonly asked questions. As 802.11ac is used with older 802.11a/b/g/n equipment, though, backwards compatibility is a concern. IEEE specifications are generally excellent at providing backwards compatibility, and 802.11ac is no exception. Many people ask me what the requirements around supporting older networks are. It’s a complex part of the 802.11 specification that has grown organically, so I will put together a post to try and explain the basics. See: A Shining Beacon in the Night: Selecting Data Rates in 802.11ac