Wireless networking is expanding beyond the next room—or from downstairs to upstairs. Standards developers have set their sights on unused television bands to create regional-area networks. Makers of fractal-shaped antennas, for their part, hope to integrate suites of wireless services unobtrusively into cars, cell phones and other devices.
The most common networks, based on Wi-Fi technology, radiate only about 100 meters from their source. Compare that with a range of kilometers for the frequencies between 54 and 862 megahertz, home to VHF and UHF television. Lower frequencies that propagate with less loss are better at penetrating foliage and buildings and are better at non-line-of-sight transmission. Hence, frequencies less than 1 GHz are better for longer-range wireless than the 2.4 GHz or higher used in current wireless networks. In 2002 the Federal Communications Commission began soliciting public comments on the feasibility of wireless network transmissions broadcasting over the largely unused frequencies separating these TV channels. Access to these frequencies would mean a huge growth in wireless service.
To pave the way for UHF wireless, the Institute of Electrical and Electronics Engineers (IEEE) has formed a working group to develop standards for wireless interoperability in the UHF channels. Led by chairman Carl Stevenson, an early pioneer in wireless standardization, the group is charged with formulating a standard, known as 802.22, specifying how wireless transmitters and receivers must coordinate so as not to interfere with one another or with TV stations. The idea is to use new technology called cognitive (or “smart”) radio capable of sensing the spectral environment. Base stations and user terminals would check for an incumbent's presence on a channel, looking for an open channel or adjusting power levels so they do not interfere with the incumbent's signal. Stevenson's group, which works closely with TV broadcasters and other licensed users, hopes to finish in early 2007. The FCC would then have to establish final rules for transmitter powers and frequencies, if it had not already.
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As wireless services proliferate, manufacturers have to figure out how to combine them into one device. The obvious approach is multiple antennas. But makers of fractal-shaped antennas contend that a single antenna might do it all. Fractals—branching shapes that look identical at all size scales—scrunch a tremendously long curve into a small space. Fractal antennas would behave like several traditional whip antennas of different lengths all twisted together, allowing them to receive multiple-frequency bands.
In 2002 a Spanish designer of fractal antennas, Fractus, partnered with automotive supplier Ficosa International to bring the technology to vehicles. Fractus supplies antennas for devices, including headsets, gaming systems and European cell phones, and the U.S.-based Fractal Antenna Systems develops antennas for defense and other applications. The joint venture, called Advanced Automotive Antennas (or A3) and now wholly owned by Ficosa, has supplied fractal antennas for the Fiat Ducato, Peugeot Boxer and Citroën Jumper. In January, A3 signed a licensing agreement with Nippon Antenna, a supplier of Mazda and Nissan. The company produces two antennas that can fit inside the external rearview mirror: a miniature AM/FM radio antenna and a triple-function antenna combining radio, the GSM cellular phone standard and GPS.
