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


Of the 470,000 Wi-Fi connections made on a recent day at Abilene Christian University, fully 94% used the 2.4GHz band, representing an extreme example of how today's surging number of Wi-Fi clients is crowding the band least able to accommodate them.
At ACU, this is not considered a problem, at least not yet. In part, that's because of careful wireless LAN design and capacity planning. And partly because a goodly percentage of mobile devices that can run on the alternative 5GHz band, do so: on that same day, 47% of the school's laptops and desktops, and two-thirds of its iPads cruised on 5GHz, via either 802.11a or 802.11n.
Yet relatively few of today's Wi-Fi clients support 5GHz.
"The challenge isn't that 5GHz-capable devices are not connecting the 5GHz band, but 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."
A growing concern
This congestion is a growing concern and, in some cases, 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 well. But it also 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, such as Dell's value-line of Inspiron laptops and its higher performing XPS line, though the latter do offer a $35 upgrade to a dual-band Wi-Fi radio.
"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 AppleMacs. About 50% of the students have them "and will connect on the 5GHz band nicely," Turner says.
"Our jobs would be easier if clients 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 partly because of decisions by radio and device manufacturers and partly 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 (though service on 2.4 is still offered). So far this year, the campus Aruba network has identified 47,000 unique 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 during peak periods in the evening users on this band see throughput ranging from 5M to 10Mbps. But 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.

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