Wireless Bridges Help Schools Boost Network Bandwidth

As the director of learning through technology for Charlotte County Public Schools in Port Charlotte, Bress is trying to rein in the cost of bringing high-speed Internet access to the district’s 18,000 students. Antennas on the towers transmit data through the air, while the sophisticated networking equipment connects the students’ computers to a broadband network backbone.

Special shielding devices keep everything from frying when lightning strikes a tower. This is a serious issue, since “It’s nothing to have more than 1,000 lightning strikes hit the area over a weekend in some seasons,” Bress says.

But the real news is the equipment that the devices protect. At the heart of this cost-saving network are wireless bridges: hardware devices that link all 21 individual local area networks (LANs) run by the district, which encompass 20 schools and the district office.

Unlike their wire-line counterparts, wireless bridges can save schools thousands of dollars by avoiding the expense of digging trenches and laying wires. And by connecting school LANs to a broadband network backbone, wireless bridges help schools cut monthly charges for high-speed communications services such as T1 lines. “By going with wireless, we save money while still supplying each of our schools with high-bandwidth networks,” Bress says.

The Charlotte County schools aren’t alone. When the Gilmer Independent School District in Gilmer, Texas, faced nearly $60,000 in digging costs to lay network wires for its high school, it opted for wireless at a fraction of the cost.

Similarly, the Kingman Academy of Learning in Kingman, Ariz., also achieved its goals when it used wireless bridges to create its wide area network (WAN). “We have been able to hook up buildings that were out of reach, funding-wise, for a wired network,” reports Kevin Chan, technology director.

The benefits are so significant that wireless LANs (WLANs) could become a key technology for elementary and secondary schools interested in both technology and bottom-line performance.

Network Togetherness

Wireless bridges typically support the Institute of Electrical and Electronics Engineers’ (IEEE’s) 802.11 standards, which define frequencies, data speeds and modulation technologies for transmitting data. Unlike access points, which wirelessly connect individual computers to LANs, bridges allow one LAN to exchange data with another to create a larger WAN. As new standards have been approved, the data-throughput speeds of wireless bridges have steadily increased.

The current speed leaders—two related standards known as 802.11a and 802.11g—allow bridges to transmit data at 54 megabits per second (Mbps), an order of magnitude faster than 56 kilobits per second (Kbps) dial-up modems. That’s speedy enough to enable schools to piggyback internal networks onto expensive T1 services leased from telecom companies—which can cost $400 or more a month—rather than running separate T1s into each school building that needs it.

But wireless WANs aren’t free of problems. The fastest wireless bridges are relatively new to the market, and their prices can bust some school budgets. Slower 11Mbps 802.11b bridges are more affordable, but at that speed, video and large graphics files can bog down a network. “Because of multimedia and streaming video, schools traditionally use more bandwidth to the desktop than the business world does,” notes Doug Prouty, technology specialist for the Contra Costa County Office of Education in Pleasant Hill, Calif.

Even modest text files and e-mail can run slower than the theoretical maximums when many people use the network simultaneously or when schools add layers of security. These loads can cause a wireless network to run at two-thirds or even half of its rated speed.

To get the best performance, wireless bridges need to be placed relatively close together—perhaps four or five miles or less apart—and have a clear line of sight uninterrupted by signal-blocking buildings or trees, explains Jim Geier, author of the book Wireless LANs.

Finally, wireless bridges are challenged by the popularity of wireless networks in general: The more wireless users there are, the greater the chance for interference as the airwaves become bombarded with messages. “Schools have installed a system and then found that someone next door is using the same frequencies,” Geier says. At that point, the two entities have to work together to find alternative communications channels that don’t interfere with one another.

Nevertheless, for some schools, the cost and performance advantages of wireless WANs far outweigh the technical tweaking that’s sometimes required.

The Bridges of Charlotte County

“Wireless makes so much sense for school districts in Florida, which tend to have a lot of land mass,” says Bress, adding that two of the 20 schools in Charlotte County are 17 miles apart. For the past year, the district has used wireless bridges to link the district office and the individual schools’ LANs.

The foundation for the WAN consists of the three 140-foot antenna towers that form a triangle from the district office to two high schools. The wireless bridges sit at ground level in protective metal cases and create three 20Mbps main trunks of the WAN. A series of building-mounted antennas and ones on smaller poles link the district’s remaining 18 schools to the WAN using 11Mbps wireless bridges.

The district office acts as a hub, where six T1 lines provide 9Mbps of available bandwidth to the Internet. “We’re massive users of the Internet in our classrooms,” Bress notes, saying that teachers regularly incorporate online educational software into their curricula. Without the WAN and Internet hub, Charlotte County would need separate T1 lines for each school.

“But a T1 has the same throughput as only about 24 modems,” he says. “Once you get 20 students using the network to access content-rich Internet sites, the WAN connection just bogs down. We needed to provide more bandwidth for the schools to enhance learning.”

The new WAN provides enough bandwidth to keep 40 to 50 students simultaneously surfing the Web without bottlenecks, he estimates.

To seal the deal, Bress compared wired and wireless WAN costs for tapping into the backbone. Charlotte pays $450 a month for its T1 lines, so running dedicated T1s to 21 buildings would cost almost $9,500 a month. Along with the backbone and Internet service provider charges, the school would have paid about $13,000 each month for what Bress considers inadequate bandwidth. “If we tried to increase bandwidth to what we got with wireless, the price would have been astronomical,” he believes.

A geographical quirk would have made wired pricing even more expensive. Three different phone companies service the areas between the district office and one of the middle schools, although the two are only about four miles apart. Wiring that school to the district office would have meant that all three of the phone companies would have billed the school district, according to Bress.

So Charlotte County went wireless. Although monthly service and equipment fees for the wireless network run about $1,200 per site, Charlotte County pays only about $10,000 a month, thanks to discounts it receives through E-Rate, a program created by the Federal Communications Commission to subsidize network upgrades for schools. E-Rate pays about 64 percent of the new network’s costs, a percentage based on the number of Charlotte County students eligible to received reduced-cost or free lunches.

Combined with the new 9Mbps Internet backbone, Bress says that his network resources have grown seven-fold. The district also would have received discounts for wired network upgrades, but in the end, Bress believes that the wired network’s performance would have been inferior. “The timing was perfect for making the switch to wireless and getting E-Rate funding,” he says.

Building Bridges

While Charlotte County must link a sprawling school district with about 18,000 pupils, Arizona’s Kingman Academy of Learning has more modest resource demands. Nevertheless, it also turned to a wireless bridge-based WAN to economically keep its 1,100 students and 200 staff communicating.

The seven-year-old charter school includes a primary school (grades K-2), an intermediate school (grades 3-5), a middle school (grades 6-8), and a high school (grades 9-10). Since the high school opened two years ago, it has operated out of a temporary building while the academy raised funds for a permanent facility to be built this year.

Rather than going through the cost and trouble of burying network wires, the academy connected the Kingman district office and its T1-based Internet service to the temporary high school building using an 11Mbps 802.11b bridge. Similar wireless bridges interconnect the three other campuses. This setup allows each student to access the Web from a PC connected to traditional wire-line LANs, which then use a bridge to go out to the wireless WAN and the Internet.

Wiring the four school facilities to the district office would have cost more than $20,000, compared to the $8,000 the academy paid for wireless, says Chan. In addition, T1 service to the four classroom buildings would have cost $1,000 each per month.

Instead, the academy pays $1,200 a month for the backbone T1 service and Internet connection, a setup that will eventually encompass the new high school as well. “The [wireless] ROI is very high,” Chan notes. “We’ll get that back within a year.” Bringing all the sites into a single network also makes network management easier, he adds.

Chan understands that the network can’t handle resource-intensive data transfers, such as streaming video, but for his school’s needs, the current arrangement works out very well. “If we eventually go to Voice over IP or something else with large data transfers, bandwidth may become an issue,” he acknowledges. “But by then, I look forward to new standards coming out that will help overcome these performance issues.”

Tunnel Vision

Texas’ Gilmer Independent School District also installed a wireless WAN at its high school. The WAN, which uses 802.11b bridges, runs from the bus garage and maintenance facilities across the football stadium to the athletic field house. A second WAN leg starts at the main high school building and travels across a parking lot to a new gym.

Using wireless technology enabled Gilmer to avoid the disruption of tearing up athletic fields and parking lots. Construction crews would have charged $58,000 for digging tunnels and laying wires, says Tony Sheridan, director of technology. “Wireless came in under $10,000 for all the [wireless] equipment and set-up,” he adds.

The school paid for its wireless network out of a $950,000 Texas school networking grant, which also included sophisticated wire-line resources, such as a fiber backbone and centralized e-mail services.

Gilmer attached all its wireless antennas to the sides of buildings. The WAN enables administrative staff located in the high school building to access servers and software in the bus garage in order to develop bus routes and reserve vehicles for field trips. The maintenance department, which shares office space in the garage, can now adjust computer-controlled air-conditioning and heating settings for classrooms and send the data over the WAN to a central computer in the district office.

Even athletes rely on the wireless network when they receive after-school tutoring in the Internet-connected classrooms located in the field house. “When the athletes are through with their tutoring, the coaches are not wondering how long it’s going to take them to get from the high school to the field,” Sheridan says. They’re right there.

All three of the school districts use encryption technology that ships with the bridges to secure their wireless WANs. The technology directors believe that securing a wireless WAN is somewhat easier than keeping hackers from stealing data or bandwidth from a wireless LAN.

“Unless someone can hover 140 feet above the ground and simultaneously spoof MAC [medium access control] addresses,” the network is safe, says Charlotte County’s Bress. If hacking techniques do become sophisticated enough to make the network vulnerable, he’ll follow suit with additional levels of encryption and virtual private networks.

For now, however, Bress feels secure knowing that, to paraphrase his 18th-century counterpart, an IT penny saved is an IT penny earned.

Source: NetDay, Speak Up Day 2003 survey results