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Case Study

802.11n the Logical Leap in Higher Ed

By: Linda L Briggs

10/21/2008

4 GHz spectrum only; the less-common but still useful 802.11a runs in 5 GHz.) On Drexel's busy urban campus, the dual-spectrum abilities of 802.11n are a real benefit, Blackney explained. That's because 5 GHz is currently a much quieter spectrum, meaning the potential for interference is far less. (Although 802.11a has long used the 5 GHz spectrum, its range and speed is far more limited than 802.11n.) For that reason, Blackney plans to deploy Drexel's new 802.11n network in that spectrum only. "We're going to deploy n in the 5 GHz base [spectrum] only. That's partly because we're in a city, so we don't control all the areas around us.... If you were a rural campus, it would be easier. But we pick up a lot of stray 2.4 GHz chatter. In 2.4, you're fighting with cordless phones, microwave ovens, Bluetooth devices, and with every consumer WiFi device that's been sold."

The 5 GHz airspace won't stay quiet forever, Blackney admitted, as more and more consumer goods operating in 5GHz are sold. But for now, he equates using 5 GHz to "moving to a quiet suburb.... We'll get a chance at a very quiet airspace in the beginning, and as we ramp up and add more signals, we'll be able to speak over that chatter."

Deploying 802.11n access points in the 5 GHz range will also make it easier for Drexel to offer complete coverage in lecture halls, often a wireless challenge because of the concentrated use. A 100-seat lecture hall, Blackney said, can typically handle perhaps three access points using either 11b or 11g before they start interfering with each other. That means a third of the room's users must share each access point, severely reducing speed. But using 802.11n offers far better speed, and moving to the 5 GHz channel allows more access points in a room, Blackney explained. Now Drexel can deploy 11 or 12 APs in a lecture hall room, with each running at speeds of perhaps 270 Mbps, rather than 11g's much slower 54 Mbps. "Once we decided we're going to embrace 5 GHz, a lot of issues that were challenging about wireless suddenly became easier," Blackney said.

Another challenge with deploying an 11n network so early is the lack of third-party tools for issues such as calculating wireless coverage and range. "In the n world, the tools are pretty awful right now," Blackney said. To address that, Drexel is rolling out the project in three phases, beginning with the law school and library. The phased approach will give them time to test coverage and adjust access point placement accordingly.


"Because the tools ... are so immature  or even non-existent now, we're doing what we are affectionately calling "Operation Duo-drop,' " Blackney said, a takeoff on Disney's Operation Dumbo Drop. "Everywhere we put a single AP in the past ... we're simply going to connect two APs with Ethernet cables, and drag them in opposite directions." By mid-2009, Blackley said he expects that tools will have caught up with the new technology, allowing a full survey and redeploy as needed.

Drexel will replace its 400 Cisco access points with 1,024 Aruba APs by the end of October. They will be managed by three Aruba modular controllers, each with a blade that can handle up to 512 access points, for an eventual capability of some 1,500 access points.


Linda L. Briggs is a freelance writer based in San Diego, Calif.