Wi-Fi devices crowd 2.4GHz band; IT looks to 5GHz

"The challenge isn't that 5GHz-capable devices are not connecting the 5GHz band, however rather the challenge is there are too few devices that have 5GHz capabilities," says Arthur Brant, ACU's director of networking service. "The 2.4GHz band is congested, a symptom of the number of devices that only operate on that band, and the limitation of its [only] three non-overlapping channels."

Growing concern and

This congestion is a growing concern and, partly, a problem on college campuses. More schools are rebuilding campus-wide Wi-Fi networks that now are designed for 5GHz. That means more costs, including half as many access points and associated cabling and ports, because the higher frequency doesn't penetrate walls as then. Nevertheless it as well means four to six times the number of non-overlapping channels, much greater capacity, and a clean radio frequency.

At a range of schools, IT staff say 50% to 60% or more of their current Wi-Fi device population, including the tidal wave of smartphones and other mobile devices, are stuck with the 2.4GHz band. [See "Wi-Fi client surge forcing fresh wireless LAN thinking".] Somewhat surprisingly, that's true for many laptop PCs, just as Dell's value-line of Inspiron laptops and its higher performing XPS line, even though the latter do offer a $35 upgrade to a dual-band Wi-Fi radio.

The difference

"Since most users don't understand the difference, they don't change this option," says John Turner, director for network and systems, at Brandeis University in Waltham, Mass. The Brandeis Wi-Fi network, based on Aruba's dual-band access points, benefits from the growing popularity of Apple Macs. About 50% of the students have them "and will connect on the 5GHz band nicely," Turner says.

"Our jobs would be easier if customers just all did a good job using the 5GHz band and left the 2.4 for other devices, like the [Nintendo] Wii and lower-power devices like smartphones," he says.

But they don't. That's in some cases because of decisions by radio and device manufacturers and in part due to the 802.11 standard, which from the outset has control of wireless access in the client radio, not the access point. More Wi-Fi brains and control is shifting slowly to the network, as vendors implement optional parts of the IEEE 802.11 standards, and the .11 working group develops new standards. [See "Major Wi-Fi changes ahead"]

At University of Massachusetts/Amherst, the WLAN for campus residence halls has been redesigned for 5GHz. So far this year, the campus Aruba network has identified 47,000 in a class by itself Wi-Fi devices, with just over one-third making use of 5GHz.

The resulting interference levels are high in the residence halls in the 2.4 band, and while peak periods in the evening users on this band see throughput ranging from 5M to 10Mbps. However clients on the 5GHz band, "regularly showed performance in excess of 20Mbps" all day, according to Rick Tuthill and Michael Dickson, network engineers with the school's Office of Information Technologies.

"We would undoubtedly like to see more customers choose 5Ghz when available, because we believe we can deliver a better experience there," says Dan McCarriar, assistant director of network services at Carnegie Mellon University in Pittsburgh. "The general perception in IT, and it matches our experience, is that 2.4GHz has become somewhat of a junk band, with all the consumer Wi-Fi routers and 'hotspot' devices that prefer it." In off-campus sites leased by CMU, "it's not uncommon to see dozens of competing SSIDs and ad-hoc devices operating in 2.4GHz frequencies, causing co-channel and adjacent channel interference and any number of other headaches."

Problem the collection of junk on the 2

Even where congestion isn't a problem the collection of "junk" on the 2.4 band can bog down performance. "The older equipment slows down the network for everyone, not just the older customers," Turner says.

Gaming systems add another, related set of problems. "These customers, like Xbox, Wii, and TiVo, have very old network cards and don't play then at all with high-speed networks," Turner says. "To tell the truth, Wii consoles require your network to support a very slow data rate - 2Mbps - or they won't even connect! In our enterprise network, those customers hang on to the 2.4 signal for dear life, in spite of our having access points near every 75 feet."

The IT groups are taking a number of steps both to build the five-lane highway and get customers to use it. As mentioned, many are redesigning their WLANs for 5GHz, creating smaller Wi-Fi cells and boosting capacity in the process, making the 5GHz signal pervasive. Wheaton College in Norton, Mass., is upgrading its dorm network from 802.11abg to dual-band 802.11n, with the access point placement based on 5GHz. "More in-depth shifting of customers to 5GHz will depend on our ability to expand 5GHz coverage," says Steven Hess, Wheaton network administrator.

Many IT staffers say Wi-Fi problems are client-related, often due to aging or badly written drivers. Often, updating the driver fixes the problem. UMass/Amherst is trying out a new program of loaning students who report particular types of network issues a replacement USB Wi-Fi adapter that supports both radio bands. If the adapter solves the problem, the student is encouraged to buy and use the same model.