Analysing the 802.11ac Wi-Fi standard – the good and the bad
There are a lot of disruptive technologies in the Wi-Fi space which promises greater speed and connection, from Hotspot 2.0, which utilises the IEEE 802.11u standard to ape cellular roaming, to 802.11ac, which was launched by the Wi-Fi Alliance in June.
Ruckus Wireless has launched a product which is claimed to be the first to be designed on the 802.11ac standard from the ground up – the Ruckus ZoneFlex R700, which can operate as either a standalone access point (AP) or in a centrally managed wireless LAN to give enterprises and providers “the ability to offer reliable, gigabit-class Wi-Fi performance.”
Craig Mathias, of mobile and wireless advisory firm Fairpoint Group, noted: “While 802.11ac promises improved performance across the board, realising that promise requires sophisticated radio frequency (RF) controls and advanced WLAN system architecture and product implementation.”
There are three elements the regulatory bodies included in the new ac standard to result in greater speed and performance; a move to 256QAM modulation, a more advanced modulation technology which results in a 30% spike in performance; more streams – the n standard has two, ac has four and potentially eight – and channel binding, meaning a mandatory 80MHz channel bandwidth in ac, compared to 40MHz in n.
Steve Hratko, director of service provider marketing at Ruckus, explained to TelecomsTech the significance of these new technologies – in particular channel binding.
“The wider the channel, the faster you can go,” he said. “And that’s literally a one to one equation here. If you run a 20MHz channel you can go a certain speed, if you run an 80MHz channel you can go four times faster.
He added: “If you track cellular, they’re going to come out with LTE-Advanced, [which] allows them to bond together licensed channels, licensed carriers, to get a higher speed as well.
“It’s becoming a common way to get higher speeds, more channels, more bandwidth.”
While the standard does promise greater performance through these methods, Hratko is quick to warn it’s not all that likely in real world environments. As Steven J. Vaughan-Nichols pointed out for ZDnet last year, the conditions you need to reach the highest potential speed of 1.3 Gbps per second “requires a laboratory, not your office.”
“Different markets are looking at it in different ways,” Hratko explained. “By and large, it’s a market that’s getting a lot of traction in the enterprise. Enterprises are looking at ac, consumers are looking at ac. It’s not that interesting to mobile operators and carriers, by and large.”
The reason why this is relates back to the channel binding. You’ll need all your channels free to make this work – which is a lot easier in an enterprise than in a public place.
“In the Wi-Fi world, in order to be a good neighbour when running unlicensed spectrum, you have to listen to the band before you can transmit on it,” Hratko added. “If I want to use 80MHz worth of spectrum, I need all four of those channels to be idle before I can transmit on them.
“But what carriers will typically do, at a street corner...there is no way you’re going to get four channels idle at the same time. It’s not going to happen – maybe at three o’clock in the morning.
“In any area where you’re not dealing with super high density, and you have control over the real estate, you can get a lot of performance out of ac,” he added.
But this isn’t the most exciting part. 802.11ac is being rolled out in two waves – the second of which will be of far more interest to operators, as Hratko explains.
“Wave two might well be the biggest thing that happens to the carrier space in a long, long time,” he said. “All Wi-Fi technologies up till now, you talk to one user at a time. You have to listen if the band is clear, then the AP can transmit or the user can transmit.
“With wave two, if you’re running a four-stream AP, each individual stream can talk to a different user. Wave two – and this is perfect for high density – is now going to talk to four users simultaneously, and receive from four users simultaneously. It’s like four access points acting as one.”
Watch this space for more on that. However the industry is slow moving in terms of regulation, if less glacial in terms of innovation. Even though the main announcement for ac was made in June, the standard was only approved in January this year.
Hratko just sees this as par for the course. “It always takes time,” he explains. “You have an ecosystem that you need to bring along, you have typically competing ideas, so it usually takes time to work it out. Often the technology’s pretty well cooked about a year before the standard’s final, but it’s the politics of standards.”
There is another factor to contend with however, which was a problem also experienced with Hotspot 2.0 – devices.
“The top of the food chain, Mountain View with Google and Cupertino with Apple, you’ve got to get on the devices,” Hratko said, adding that Hotspot 2.0 was ready “about a year before the devices were ready.”
“There’s a big ecosystem, all the AP vendors have to get on board with it, set a lot of standards, then it has to be picked up by device manufacturers,” he added.
The Ruckus ZoneFLex R700 ships at $1295 and is available worldwide. You can find out more about it here.
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