May 2006

A Cell-Phone Tower with Focus

By Wade Roush

When you talk on a cellular phone, you're sharing radio frequencies with everyone else within a three-kilometer radius of the nearest base station. Congestion can lead to static, dropped calls, and slow downloads. In the basement of Nokia Research Center in Helsinki, Finland, Nokia has forged a new kind of antenna that focuses signals where most needed and could triple network capacity.

A traditional cell-phone tower works like a lawn sprinkler that radiates in all directions. Nokia's antenna works like a hose. It's fashioned out of copper strips, each about eight centimeters wide, welded together into a surface covering about one square meter. A case behind the copper sheet contains sophisticated amplifiers and digital signal-processing circuits that steer as many as eight separate beams in different directions, depending on demand. "The basic idea is that in a crowded area, you want to give the maximum signal to the appropriate person rather than wasting the energy by spreading it out over a broader volume," explains Greg Hindman, presi-dent and cofounder of Torrance, CA-based Nearfield Systems, which builds testing and measurement systems.

While the antenna could theoretically multiply network capacity by a factor of eight, geographical obstacles and other sources of interference mean it actually doubles or triples capacity, says Hannu Kauppinen, senior research manager for radio technologies at the research center.

Nokia is not alone: many telecom researchers are working on ways to increase the capacity of the newest generation of cellular networks, called wideband code-division multiple-access, or WCDMA, systems.