Wireless Networks | Feature
How Georgia Tech Serves Up High-Performance WiFi to 40,000-Plus Devices
Large concentrations of mobile devices can cause interference and connectivity issues. Early adopter Georgia Tech is solving the problem with focus-beamed antennas for its large-capacity classrooms.
These days, the average college student brings three devices to the campus environment and expects to have seamless connectivity to the Internet without any interruption in service. Mobile devices are creating a dramatic acceleration in data traffic and pushing networks to their limits — especially where there are large concentrations of simultaneous users in auditoriums, lecture halls and large classrooms.
Fortunately, there is an answer: high-density, narrow-beamwidth antennas that reduce channel-to-channel interference, increase capacity and enable stronger and more reliable WiFi signals.
"On a typical day, we have more than 40,000 unique client devices using our wireless network on campus," said Bill Lawrence, IT project manager principal at Georgia Institute of Technology. "We were experiencing issues with poor client performance in several large auditoriums across campus, particularly with too many clients on too few wireless access points. We were also seeing uneven client distribution across the access points that were in the rooms." There were complaints that performance was very degraded, almost to the point of being unusable.
Lawrence and his team had started out with internal omni-directional antennas. "An omni-directional antenna is like an incandescent light bulb," explained Lawrence. "The light goes everywhere." Needing to focus the radio signal into a certain space, the IT team researched wireless vendors and elected to go with directional antennas from TerraWave Solutions, a division of Tessco Technologies. "The TerraWave antenna is like a flashlight or a spotlight," Lawrence said. "It focuses energy where you want it to go."
TerraWave high-density antennas are external antennas that connect to all of the industry's leading access points. For WiFi users in indoor and outdoor large public venues, these antennas increase capacity and optimize coverage by providing a narrower, focused beam of coverage that enables stronger, more reliable WiFi signals. The antennas also reduce channel-to-channel interference.
To address issues of interference and connectivity, high-density networks are designed to provide small RF (radio frequency) cells of operation, explained TerraWave product manager Dennis Burrell. "These small RF cells are achieved by using narrow-beamwidth antennas [35 degrees vs. the traditional 50-80 degrees] on the access point. This limits the users per access point, which in turn increases the bandwidth available to each user."
The TerraWave High-Density 2.4/5 GHz Patch Antenna — about the size of a small pizza box — is installed on the ceiling or the wall, depending on where the access points are located. In order to determine how many antennas are needed, a school considers the number of devices they want the network to support; the applications the network supports (Internet research, e-mail access, shared online classroom resources, etc.); and the throughput (amount of data) needed for each of those applications.
Georgia Tech did a pilot project involving two 300-seat auditoriums during this year's spring break. Based on promising results, the school used the same solution in several large auditoriums across campus last summer.
Since then, Lawrence and his team have installed 279 high-density antennas. The installations took place in 48 rooms, within 21 campus buildings. The upgraded rooms seat anywhere from 83 to 348 students.
"This will be the model we use going forward, for large classrooms and auditoriums," explained Lawrence. "I used this antenna/access point combination for an outdoor courtyard this semester, and have plans to use it in other outdoor locations, provided funding becomes available."
Since the installation, the team has seen a significant reduction in the number of complaints regarding a slow wireless network. "We're shooting for about 25 people per wireless access point/antenna. It's not as nice and clean as that, but that's the metric. The actual number may be more or less." The issue they've run into is that the spotlight analogy is not quite that "clean" when it comes to radio signals, which tend to "bleed out," Lawrence explained. "We can't get them too close together or they will interfere with each other. The more you focus the beam, the more problems associated with it."
Still, after doing a survey of two of its large auditoriums, and some empirical testing, the school has found that it now has better performance on its wireless networks. Rather than hearing complaints that the "network is junk," a typical problem these days is authentication — a much easier problem to resolve.
Going forward, Lawrence has recommendations for other schools considering narrow- beamwidth antennas. "I would say get with your wireless equipment vendor and utilize some of their expertise," advised Lawrence. "That's one of the things we did, because it's not just a matter of installing the antennas. The antennas are only part of the equation. The access point and controller settings are just as important. I would say, do a pilot project like we did, and then monitor the network to see if things improve. You also have to deal with channel management because there are a finite number of channels available, and co-channel interference can severely degrade the network performance."
"As far as budgeting is concerned," Lawrence continued, "you need to be creative and look for funding sources. We've worked with our Facilities and Campus Planning departments to incorporate wireless funding into the construction and renovation budgets. We also partner with the different colleges and schools on campus for funding. In addition, we have a student technology fee." The money from this fee is used for instructional technology.
"We've been installing wireless networking on campus since the late 1990s and this is the first year we've actually had a dedicated wireless budget," concluded Lawrence. "We don't always get funding, and sometimes, when we do, it's not all we ask for. But we keep at it."