The U.S. Military Academy at West Point is deploying an 802.11a, 54M bit/sec wireless LAN as part of a new strategy to create a much more interactive classroom, where cadets are not simply passive listeners to an information broadcast by a teacher, but active participants. A high-speed wireless LAN is one element in creating this interactivity.
Traditionally, a professor would explain why it was so important for Col. Joshua Chamberlain to hold the Union Army’s left flank at Little Round Top during the Civil War Battle of Gettysburg. But with the wireless classroom and a variety of specialized applications on laptops and servers, cadets can run a computerized simulation to see the consequences of failing to hold that critical hill.
Wireless LANs are making it cost-effective for the academy to give each student this capability, says Col. Donald Welch, the academy’s associate dean for information and education technology. “It would be a lot more expensive, and much less flexible, to make every classroom ‘information rich’ by wiring desktop computers [instead of using wireless LANs],” he says.
In the fall of 2002, the academy deployed a large-scale pilot network of 105 802.11a access points from SMC Networks, covering classrooms in the biggest academic building. Based on that experience, the IT group deployed the wireless net in two other buildings and is working now on the fourth. By August, when the Class of 2007 enters, there will be 369 802.11a access points, one in every classroom and lab. Every cadet will have a wireless laptop.
There were two interrelated reasons for choosing 802.11a, Welch says – higher bandwidth and throughput, and eight nonoverlapping channels for clients, compared with three channels for 802.11b. When channels overlap, the interference causes throughput to plummet. To create 802.11b wireless “cells” with nonoverlapping channels on multiple floors in a building, we have to spread out the access points, Welch says. That means more users per access point, vying for a throughput of, typically, about 5M to 6M bit/sec.
“With 802.11a, we can put an access point in every classroom, and there’s no more than 19 people sharing that higher bandwidth [throughput of roughly 17M to 21M bit/sec],” Welch says.
The academy’s IT group evaluated four 802.11a vendors. “SMC is a low-end access point, without much in the way of bells and whistles,” Welch says.
By contrast, another vendor offered more features, but at five times the cost. More importantly, all the products performed alike. “We found negligible differences in performance, in terms of throughput, [network] latency, flexibility and so on,” Welch says.
Initially, Welch thought that the deployment issues would be things such as security, the unique qualities of radio frequency as the medium and so on. But all those proved “relatively easy,” he says.
“The big problem was setting up the student machine with the wireless [network interface card], and the security software [from Cranite Systems],” Welch says. “But then the student messes around with the machine and messes up the [wireless] configuration. We hadn’t considered this.”
A second lesson was figuring out how to keep the wireless net running, and handle any problems, with an IT support structure designed for a wired net. Limited by various organizational requirements, he pulled together staff from various groups and departments and created a kind of “virtual” support organization. All members of this team were given a basic training in wireless technology, and there is a clear structure and procedure for identifying problems and referring them to the team’s wireless experts.
Security is based on Cranite’s WirelessWall gateway software, which runs on Linux servers. WirelessWall incorporates a firewall and mutually authenticates client and access point over an encrypted tunnel. Cranite scrambles all information on the network, including IP header information, with the Advanced Encryption System, which is far stronger than the standard Wired Equivalent Privacy that’s part of the 802.11 standard.
For management, the IT group is using Cisco net management products, along with some utilities from SMC. The wireless team has just gotten its hands on two protocol sniffers, specifically designed for 802.11a wireless LANs.
The sniffers are critical to quickly troubleshoot any reported problems. In the future, the sniffers will let network administrators continually fine-tune the network’s performance. “My wireless guys are saying, ‘We have got to have this,'” Welch says.
