Tech Guide: Next-generation 802.11ac Wi-Fi

Summary:It's too early for businesses to adopt 802.11ac, but this high-speed 5GHz wireless standard offers enough advantages, especially for BYOD, that you'll want to start planning soon.

The first consumer access points, media bridges and USB adapters using next-generation 802.11ac Wi-Fi are coming onto the market — at the same price as today's high-end 802.11n models — and the first notebooks with 802.11ac built in were announced at Computex this month. 

It's too early for businesses to adopt this higher-throughput, less-contended 5GHz wireless standard, which won't be ratified until February 2013. However, 802.11ac offers enough advantages, especially for BYOD, that you'll want to start planning soon — particularly as it will also require more sophisticated network architecture to make the most of it.

Buffalo's Airstation 1750 is the first 802.11ac router on sale in the UK: it has a headline data rate of 1.3Gbps in the 5GHz frequency band, although real-world throughput is much lower

Less than gigabit speeds, more than video streaming

802.11ac promises wireless networks at gigabit speeds, using the same 5GHz spectrum as 802.11n (which can also operate in the crowded 2.4GHz band), but with channels that are 80MHz (or even 160MHz) wide rather than 40MHz and eight spatial streams rather than four. Theoretically, 802.11ac speeds could go up to nearly 7Gbps, but that's not what we'll see initially. The first products only have three spatial streams, and the theoretical maximum speed is 1.3Gbps (3 x 433.3Mbps streams with 80MHz channels). That's still a lot faster than 802.11n speeds, which can reach 450Mbps with three spatial streams (3 x 150Mbps streams with 40MHz channels). You can rely on the throughput you see in practice being a fraction of the physical (PHY) data rate, but even early 802.11ac devices are showing significant speed improvements over 802.11n.


Real-world 5GHz 3-stream, 80MHz-channel 802.11ac performance (top dotted line) versus 5GHz 3-stream, 40MHz-channel 802.11n (lower dotted line)

When Buffalo demonstrated a prototype 802.11ac device at CES this January in a relatively 'clean' environment with little interference, we saw speeds ranging from 776Mbps to over 800Mbps. In our tests of Buffalo's AirStation 1750, the results were less startling but still impressive (see above): throughput remained at around 100Mbps at distances up to 10m, falling to just under 20Gbps at 30m. By contrast, a 3-stream 802.11n connection in the 5GHz band declined fairly linearly from 60Mbps at 1m to zero at 30m.

Just because 802.11ac is initially focused on consumer devices doesn't mean that businesses can ignore it. In fact, with the rise of BYOD, getting good connectivity to consumer devices is important for businesses — especially if users get 802.11ac at home and complain that wireless is slower and uses more battery power when they're in the office.

Just because 802.11ac is initially focused on consumer devices doesn't mean that businesses can ignore it. 

Those speeds will enable faster backups, faster access to cloud resources and make video conferencing and unified communications feasible (especially with improved hotspot connection standards that we'll be hearing more about towards the end of this year). And video streaming isn't purely a consumer benefit either, as Matthew Gast of Wi-Fi hardware supplier Aerohive points out.

Tablets like the iPad and ultrathin notebooks like the MacBook Air don't have Ethernet and VGA ports, so unless your projector has an HDMI connection and you have the right adapter, it's hard to give a presentation. Wireless projection and AirPlay desktop beaming solve the problem. "That's a form of video streaming that's very relevant to the enterprise," says Gast.

Slower devices benefit most

Don't focus just on the higher speeds that 802.11ac offers more powerful devices, says Perry Correll of enterprise Wi-Fi hardware supplier Xirrus. It's equally important that slower devices get a speed boost. "Wireless in a mid-range laptop today can give you up to 450-megabit-per-second throughput," he explains. "But tablets, even though they do 802.11n, peak out at 65 megabits, and out of that maybe only 25 megabits is usable. People are expecting these devices to be usable in the office, and they're not."

With 802.11ac, a tablet would get more like 200-250Mbps "actual, usable throughput", Correll says. In recent tests, he saw one smartphone vendor achieving "220 megabits stable throughput on a smartphone — that's in a pristine test environment, but in actual use, if I can get 150 megabits of usable throughput that's five to six times more than the typical smartphone or iPad today".

Even in a small office, bandwidth on an 802.11n network will fall off sharply when four or five devices are connecting at once. With multi-user MIMO in the second- and third-generation chipsets, 802.11ac offers higher aggregate bandwidth to multiple devices by allowing the radio to talk to devices at different speeds at the same time. A notebook getting 450Mbps isn't handicapped by slower phones and tablets connecting to the same access point.

By enabling higher speeds, 802.11ac also saves power. "You have a lower energy per byte because you have higher efficiency at the same transmit power," says Brian Verenkoff of Buffalo Technology. "The radio can get to sleep much quicker because it sends so much more data in that time". That's showing up in tests, according to Xirrus's Perry Correll: "Not only does 802.11ac give more performance on small devices, but also in some testing it's been five times more economical of battery life".

This combination, says Corell, is why manufacturers like Apple, Samsung and RIM are pushing 802.11ac — not just chip-makers and access point vendors. Lower power consumption makes 802.11ac attractive for the embedded and machine-to-machine market too, and that massive scale will help drive prices down.

Wireless networking has come a long way since the early days of 2Mbps 802.11 in the late 1990s; 802.11ac equipment with a physical (PHY) data transfer rate of 1.3Gbps is just beginning to appear, which should prompt well-prepared businesses to plan for a new generation of high-speed wireless networks

Plan ahead

It's far too soon for businesses to go shopping for 802.11ac kit: enterprise-grade access points won't be available until the first quarter of 2013, and those will have early chipsets that don't offer the highest data transfer rates and multi-user MIMO aggregation that businesses will want. Correll suggests waiting until the second quarter to buy — but he also advises that you plan your wireless architecture well in advance, because this will need to be very different for 802.11ac networks. 

"For twenty years, network admins have been careful about how they design the wired network", says Correll, "but for wireless they're putting a couple of APs up on the wall and saying if there are problems users can just go back to the wired network. Gartner says that 80 percent of the networks designed today are going to be obsolete with 802.11ac — if you just put up an access point every ten rooms, you're going to fail."

Businesses will need to design their wireless infrastructure to support much higher data loads.

Between more devices per user and better wireless throughput, businesses will need to design their wireless infrastructure to support much higher data loads. Correll suggests assuming that the amount of traffic going through an access point will increase by five or ten times, which means a change of approach. "Today [companies] deploy access points with a single controller handling all traffic and with five or ten times the load, that whole centralised controller architecture is a problem — it becomes a tremendous choke point. You have to distribute the processing; each access point will have to support its own traffic without flowing to back the controller."

One of the ways 5GHz Wi-Fi reduces interference is by having smaller coverage areas, which also affects your planning. "Phasing and beam-forming will help to extend the range more than 5GHz 802.11n solutions, but it's marginal", admits Buffalo's Verenkov. This means you'll still need to plan your AP placement carefully.

Wi-Fi hardware needs to be more sophisticated to get the most out of 802.11ac, cautions David Callisch of enterprise Wi-Fi supplier Ruckus Wireless. Standard omnidirectional antennas will cause some of the same interference problems from devices and other access points that we see in the 2.4GHz spectrum. Access points need to offer predictive auto-channel selection, which chooses channels based on throughput capacity, and also need to mitigate interference with high-gain directional antennas. Instead of individual access points, consider modular arrays where you can plug in a new network standard: you'll be able to use the same chassis for 802.11ac next year, and future standards like 802.11af and 802.11ad in two years' time.

That's a long way from the first consumer 802.11ac units, but those are what will push your company towards this new way of deploying Wi-Fi.

Topics: Reviews


Mary Branscombe is a freelance tech journalist. Mary has been a technology writer for nearly two decades, covering everything from early versions of Windows and Office to the first smartphones, the arrival of the web and most things inbetween.

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