Wireless

Drexel Sees 802.11n as Logical Leap

• By Linda L. Briggs
• 08/07/08

For colleges and universities considering a wireless network upgrade anytime soon, whether or not to go with the new, not-yet-final 802.11n standard is a tough call.

On one hand, the new protocol offers tantalizingly fast raw data rates of up to 300 Mbps in best-case scenarios, along with multiple antennas for better performance, the ability to run in either the 2.4 GHz or 5 GHz spectrum, and other design improvements. That's a dramatic leap from the current fastest WiFi standard, 802.11g, which runs at up to 54 Mbps and uses the same 2.4 GHz spectrum as 802.11b.

Also on the plus side, many newer notebook computers are already 802.11n draft spec-compliant, so plenty of students and faculty are ready for the new standard, even if campuses aren't.

On the other hand, the final standard won't be approved until 2009. That leaves the door open to last-minute changes, although most observers agree that any major alterations are unlikely at this point. More to the point, with few campus deployments yet, higher education administrators don't have many examples to turn to for best practices in an 802.11n rollout.

Drexel University, a traditionally technology-heavy campus in the heart of Philadelphia, weighed the odds and has decided to jump to 802.11n, beginning with a limited deployment this summer. Drexel has chosen to work with Aruba Networks, which employs the 802.11n standard in its Adaptive Radio Management (ARM) technology. When it is complete this fall, Drexel's new wireless network will serve more than 40,000 wireless devices running either 802.11a, 802.11b, 802.11g, or 802.11n, making it one of the largest 802.11n deployments yet in higher ed.

To Kenneth Blackney, associate vice president of core technology at Drexel, upgrading to 802.11n made sense. "You really have a choice whether you're going to believe in n or not," he said. "If you don't, you're going to deploy the same stuff you could have deployed four years ago. That's really not much of a leap."

Blackney said he isn't overly concerned about potential changes to the draft standard between now and when the final protocol is released by the international committee that manages wireless standards. In his opinion, too many wireless vendors have invested too much in the 802.11n standard now for any major changes to occur. "I look at this in terms of the economics for the companies making the infrastructure gear and the end-user gear.... It's Drexel's opinion that the cost of the standard not fitting what has already been deployed is too high, [so] those vendors are going to make it work, or they're going to find some ways to retro-fit [devices] with new firmware."

One big strength of 802.11n is that it runs in two wireless spectrums--both 2.4 GHz and 5 GHz. (The 802.11b and g standards run in the 2.4 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.