Wireless Beyond the Ivy-Covered Halls

Is your campus ready for ubiquitous wireless network access? Here’s all you need to know about the pros and cons of today’s technologies.

HAS YOUR ADMINISTRATION tossed you the ball, saying, “Let’s provide wireless networking outdoors on campus and to students, faculty, and staff residing off campus”? If so, can you toss the ball back with: “We’re already doing that”? Or if not, do you know how you’d answer that request?

Notre Dame

CAN YOU SPOT the cell sites in this photo?
At Notre Dame, ‘stealthy’ antennas ensure
the cell system stays out of sight.

While most institutions have provided wireless networking within campus buildings, availability outside those walls is either nonexistent or in early stages. Yet the capacity for ubiquitous wireless access is in reach, and its implementation can have numerous benefits. Business drivers include: making your campus more attractive to students, faculty, and staff than your competitors’; potentially increasing productivity due to improved access to campus resources; and the potential to save costs by boosting your percentage of automated transactions, because the point of entry for wireless users could be the campus web portal.

Following is a brief technical primer on the current wireless technology options and their associated caveats. (For a summary of key concerns, see “Outdoor Wireless Technologies: 6 Caveats.” ) Technologies include WiFi, proprietary, and cellular/PCS-based (as well as future WiMAX); topology options include hot spots, fixed point to multipoint, and meshed networking. Key factors to consider when deciding which option(s) to select are throughput (speed), line of sight (LOS) requirements, and frequency availability/interference.

Licensed vs. Unlicensed Frequencies

Every type of wireless technology, including cellular, is assigned to certain frequencies in the radio spectrum. The Federal Communications Commission controls the assignment of frequencies. In the US, most frequency ranges require a license from the FCC (such as for cellular frequencies), which comes at some cost. But the FCC also has set aside a small amount of spectrum for unlicensed, no-cost use. All WiFi or 802.11 technologies use unlicensed frequencies in either the 2.4 GHz or 5.8 GHz range. While these frequencies are freely available, one downside is that there are no guarantees against interference, so your wireless network could be overcome by a stronger, nearby signal, and you would have no legal recourse. Another disadvantage is that there is relatively little unlicensed spectrum available, so as more and more unlicensed networks are built, interference becomes likelier.

WiFi Hot Spots

These hot spots are familiar to anyone who has taken advantage of wireless networking at a coffee shop. Although WiFi throughput can be quite good—at 6-24 Mbps, under near-perfect conditions—two key concerns about this technology are 1) interference, due to the unlicensed nature of the available frequencies, and 2) line of sight issues. (“Line of sight” refers to a clear path between the transmitter and the receiver; literally, you should be able to see from one to the other with no obstacles even partially blocking the path.) The ever-changing nature of hot spots owned by others increases the cost of maintaining your own off-campus hot spots, which makes this technology less attractive. However, outdoor oncampus hot spots, if carefully planned and designed, are relatively inexpensive and could be melded into your existing campus network.

Cellular/PCS

Early versions of cellular data service were so slow as to be practically useless, but this is changing. Current offerings provide end-user bandwidth of 300 Kbps to 1.2 Mbps downstream (much superior to a modem and nearly as good as DSL). The key advantages of this technology, from a campus perspective, are that it is already quite pervasive (similar to cell phone coverage), no campus support is required, and there is little or no start-up cost. The primary downside is the fact that you are limited to whatever coverage your carrier’s network provides.

Dewitt Latimer, deputy CIO and chief technology officer at the University of Notre Dame (IN), overcame this last problem by inviting cellular providers to participate in a carrier-neutral distributed signal system. Cell providers had been itching to get into the university’s athletic venues, but Notre Dame has a strict policy against cell towers on campus property. The new system places 16 mini cell sites across campus (including classroom buildings and dorms) with “stealthy” antennas (camouflaged to look like lamp posts or other common tall objects). A third-party vendor (NextG Networks) maintains the system and negotiates and coordinates with the carriers. Notre Dame supplied some dark fiber to interconnect the mini cell sites and is compensated for space it provides to house the vendors’ equipment.

Point to Multipoint (PMP)

This wireless topology is in use in scores of locations across the US, and is less expensive than other large-coverage-area options at today’s cost points. PMP may use either licensed or unlicensed frequencies, depending on the manufacturer. And PMP uses a “base station” topology, in which antennas are sited on one or more tall towers from which signals are sent and received—usually in six sectors of 60 degrees each. (Think of a circle with three lines through it to create six pie-shaped coverage sections.)

Outdoor Wireless Technologies: 6 Caveats

1. Technological change is a constant. Plan for major upgrades every three years.

2. All wireless networks are shared media, so the more users in any given coverage area, the less bandwidth each will have.

3. Although wireless throughput rates keep increasing, so do rates for transmission via fiber-optic cabling. If you need a high-speed, reliable backbone link, think fiber first.

4. An outdoor wireless signal can’t penetrate far into buildings, so if networking is desired throughout a building, an internal LAN or WiFi network would still be needed. Reception in high-rise buildings is a special problem.

5. Wireless networks operate on radio frequencies (RF). Designing coverage areas for RF is as much an art as a science. Best case: 95 percent coverage.

6. Most wireless systems require a clear line of sight (LOS) between the transmitter/receiver units, although some manufacturers now can offer “near line of sight.” The difference is significant, so always verify!

In this type of network, each end user must have an antenna/receiver (usually proprietary to the manufacturer of the PMP system) at his site, pointing at the base station; a line of sight between the two is required. PMP can provide approximately 600-800 Kbps of twoway service per end user. Cautionary note: Although PMP systems are still available for sale, there have been no new installations. It appears the market is moving away from this mostly proprietary technology and toward meshed networking.

Meshed Networks

A meshed network topology permits multiple lower-capacity radios to interconnect, thus allowing greater coverage, plus some ability for the network to “heal itself” when a node fails. BelAir Networks, Cisco Systems, Motorola, Proxim Wireless, Strix Systems, and Tropos Networks are all manufacturers of WiFi-based mesh networking equipment. As of June 2006, Tropos has the largest installed base of larger-scale mesh networks. For a good, basic understanding of mesh networking technology, see the white paper here.

Funding?

Stay tuned for general wireless cost considerations in a future column. In the meantime, to help your staff and students living off campus, why not forge a mutually beneficial arrangement with the city in which your campus resides? Municipalities often have good reasons (which usually include improved public safety communications) to implement outdoor wireless networks, and many are exploring their options right now. This option should at least be in your playbook.

comments powered by Disqus