Wednesday, February 22, 2006

Faster than Fiber

A new wireless technology could beat fiber optics for speed in some applications.

By Kate Greene

Atop each of the Trump towers in New York City, there's a new type of wireless transmitter and receiver that can send and receive data at rates of more than one gigabit per second -- fast enough to stream 90 minutes of video from one tower to the next, more than one mile apart, in less than six seconds. By comparison, the same video sent over a DSL or cable Internet connection would take almost an hour to download.

This system is dubbed "WiFiber" by its creator, GigaBeam, a Virginia-based telecommunications startup. Although the technology is wireless, the company's approach -- high-speed data transferring across a point-to-point network -- is more of an alternative to fiber optics, than to Wi-Fi or Wi-Max, says John Krzywicki, the company's vice president of marketing. And it's best suited for highly specific data delivery situations.

This kind of point-to-point wireless technology could be used in situations where digging fiber-optic trenches would disrupt an environment, their cost be prohibitive, or the installation process take too long, as in extending communications networks in cities, on battlefields, or after a disaster.

Blasting beams of data through free space is not a new idea. LightPointe and Proxim Wireless also provide such services. What makes GigaBeam's technology different is that it exploits a different part of the electromagnetic spectrum. Their systems use a region of the spectrum near visible light, at terahertz frequencies. Because of this, weather conditions in which visibility is limited, such as fog or light rain, can hamper data transmission.

GigaBeam, however, transmits at 71-76, 81-86, and 92-95 gigahertz frequencies, where these conditions generally do not cause problems. Additionally, by using this region of the spectrum, GigaBeam can outpace traditional wireless data delivery used for most wireless networks.

Because so many devices, from Wi-Fi base stations to baby monitors, use the frequencies of 2.4 and 5 gigahertz, those spectrum bands are crowded, and therefore require complex algorithms to sort and route traffic -- both data-consuming endeavors, says Jonathan Wells, GigaBeam's director of product development. With less traffic in the region between 70 to 95 gigahertz, GigaBeam can spend less time routing data, and more time delivering it. And because of the directional nature of the beam, problems of interference, which plague more spread-out signals at the traditional frequencies, are not likely; because the tight beams of data will rarely, if ever, cross each other's paths, data transmission can flow without interference, Wells says.

Until a few years ago, the use of these electromagnetic frequencies that have enabled Gigabeam to build a higher-speed network, were off-limits for two reasons. First, the Federal Communication Commission (FCC) approved public use of these high frequencies only in 2003, says Wells. When the FCC finalized the agreement in 2005, GigaBeam began to ship prototypes.

Second, there was no cost-effective material for making transmitters at such frequencies. Wireless transmitters that send traditional signals are made of silicon, which can't operate at frequencies in GigaBeam's range. Within the past few years, Wells says, manufacturing techniques for making high-frequency radio transmitters out of gallium arsenide have improved significantly, making the technology less cost prohibitive.

While working at these frequencies permits high-speed data rates, there's an intrinsic physical challenge: molecules in the atmosphere absorb energy at certain frequencies. To deal with this, GigaBeam exploits those frequencies that are less susceptible to absorption by air and water molecules.

But the technology is still susceptible to heavy rains. In arid conditions, Gigabeam's signal can travel about 10 miles, but in areas where heavy rains occur, says Wells, the company's radios are only guaranteed to push a signal for about a mile, with the transmission will be down for a maximum of only five minutes per year.

Even with its advances, though, Gigabeam faces the same problem as other point-to-point technologies: creating a network with an unbroken sight line. Still, it could offer some businesses an alternative to fiber optics. Currently, a GigaBeam link, which consists of a set of transmitting and receiving radios, costs around ,000. But Krzywicki says that improving technology is driving down costs. In addition to outfitting the Trump towers, the company has deployed a link on the campuses of Dartmouth College and Boston University, and two links for San Francisco's Public Utility Commission.