Wireless: What Works?
By Wendy Chretien
Thinking beyond Wi-Fi (and no, this is not another hype of WiMAX), an emerging option you should know about is very high frequency (71-76 GHz, 81-86 GHz, and 91-95 GHz), very high capacity licensed wireless. The technology is known as millimeter wave or E-band, and the FCC also refers to it as “virtual fiber.”
At these recently-made-available frequencies, the overall bandwidth capacity is much greater than traditional radio frequency communications, even microwave. These focused, line-of-sight, Gigabit/second signals can be set up in point-to-point configurations for distances of up to a mile. Sounds great, no?
So what’s the catch? If you’re a skeptic, like I am, you’ll have noted several potential caveats in the above description, namely “licensed,” “emerging,” “line of sight,” “point to point” and “up to a mile.” “Licensed” tells us that one must obtain a permit from the FCC in order to use this type of system. (I can hear the groans at this realization.) What may surprise you, though – especially if you’ve ever struggled with these types of permits in the past – is that the process for obtaining the permits for these frequencies has been moved online and is now greatly streamlined. Now a license can be secured within days, not months.
From the customer’s standpoint, “emerging” can mean buying into proprietary systems. Often, it means that there are few vendors of the technology, thus limiting competition and ultimately equating to high prices. These are real risks you will need to decide to take or not; if you use this technology for selective purposes, however, the risks may be moot.
“Line of sight” is probably the most significant barrier to the use of millimeter wave technology because there must be no physical barriers between the sites you plan to connect. Trees, for instance, can be a significant barrier. You truly need to be able to stand at point A and clearly see point B (and yes, it’s legitimate to use binoculars or a telescope). Unlike most implementations of Wi-Fi, E-band wireless d'esn’t blanket an area around the antenna, but rather, shoots a highly directional, “pencil-beam” connection to another antenna/receiver. That means this technology is best suited to direct building-to-building connections, also known as point to point. The real advantage of focusing the beam is that the traffic-carrying capacity increases by an enormous amount. E-band can carry up to 2.7 Gigabits/second of information (this is the claim; your mileage may vary). This is a previously unheard-of capacity for wireless technology. Only Free Space Optics (which is light-based rather than radio-frequency-based – and therefore also technically wireless) comes close. We’ll cover that soon.
The distance limitation is a matter of physics. Radio frequency signals can travel only so far before they are absorbed by the atmosphere. (In the wireless world, this phenomenon is known as “attenuation.”) Every type of wireless signaling is subject to this law of physics. Still, around a mile is sufficient for most campuses.
Even after all of the possible “gotchas,” this technology truly has something to offer – namely, it can be an excellent substitute for a relatively short run of fiber when a fiber installation would be extremely tricky, time-consuming, or costly. It can also act as a backup to an existing fiber link or serve as an upgrade to an existing point-to-point wireless link that has too little bandwidth for current and future needs. In short, d'esn’t your campus have a need for this?
One of the first companies to market in this new arena is GigaBeam Corp., which started business in 2004 and already boasts four higher education customers: Boston University, Dartmouth College, Oklahoma State University, and the University of Maryland. BU and OSU each have a building link used to transport medical files, including radiographs (“x-rays” to most of us). Dartmouth and Maryland make use of the large-capacity links for data communications between sites.
GigaBeam claims “reliable point-to-point two-way communications at up to 2.7Gbps with 99.999 percent weather availability for about a mile or more” and calls its product WiFiber. The products currently available provide up to 1.25Gbps capacity.
This skeptic needed some real-life input, so I conducted a reality check with David Bucciero, the company’s director of Technical Services, and Kathy Frazer, the manager of Technical Services at Dartmouth College. According to Bucciero, “Dartmouth has a reputation as one of the most unwired campuses in the nation and as being on the leading edge in technology, [thus] the use of millimeter wave technology can be considered an extension of that.”
Dartmouth also happens to be in a location where installing fiber is problematic. There’s too much granite to bury it cost-effectively, and the owners of utility poles in that area set a high value on the use/leasing of that real estate. So when the college determined it needed a high-capacity link to the Dartmouth Hitchcock Medical Center (DHMC) and needed to get it up and running quickly, Technical Services looked at a number of wireless alternatives. DHMC had a leased ATM connection, and the backup to that was via satellite, which could not provide sufficient bandwidth if the primary link failed. Due primarily to the available data rate, the college selected the millimeter wave solution.
The initial installation of the system was up in just a few days. But after a short time, the college was seeing loss in the link. GigaBeam sent technicians who diagnosed the problem and stayed on site until it was corrected. Since that first glitch, the system has been running smoothly and is now used as an always-on system, which load-shares with the leased circuit. The satellite connection has since been discontinued.
After that success, the college added another link between ISTS and the new Rugby Clubhouse. In this case, the line of sight was somewhat marginal. The GigaBeam technicians warned Dartmouth’s Technical Services that growth of trees could be an issue, and it was. To resolve the problem, the college recently increased the height of the pole on which one antenna is mounted. The new link is now the only connection between the buildings and is functioning as advertised. In fact, Dartmouth is running Cisco voice-over-IP (VoIP) phone traffic over this link. And Technical Services is considering a third implementation.
Because Wi-Fi and millimeter wave use completely different frequency ranges, there’s no need to worry about interference between them. In fact, E-band could become a backhaul facility for an otherwise isolated building in which you’d like to install Wi-Fi but haven’t because there hasn’t been a feasible way to connect it to the rest of the campus.
A single link between two sites costs about $50,000. If that number seems high, compare it to the cost of burying new fiber along a mile-long route, which typically starts at $75,000, but can be as high as $250,000 in an urban environment. (According to Bucciero at Dartmouth, the millimeter wave system had an ROI of less than eight months, compared to fiber.)
As is typical in the technology arena, you can anticipate that costs will decrease as more manufacturers bring products to market. L'ea Corp. – truly a pioneer in the market since its inception in 2000 – has a number of users, including the Hawaii Institute of Marine Biology.
To sum up, if there’s a pressing need for high-capacity wireless on your campus now, E-band/millimeter wave/“virtual fiber” may be the right choice for you.
Wendy Chretienis is a Network Systems Consultants with Elert & Associates, an independent technology consultancy.