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Stanford U. Research Could Eliminate Cellphone Dead Zones

Cellphone dead zones might soon become a thing of the past.

Technology developed by three graduate students in engineering at Stanford University could allow wireless systems, including telephone and WiFi networks, to simultaneously send and receive information, doubling their speed and improving their performance—and keeping them from deafening themselves.

As it is, a signal transmitted through a network is stronger at its point of origin than incoming signals are. In essence, each end of a network is talking so loudly it can’t hear what the other end is saying.

Philip Levis, an assistant professor of computer science and electrical engineering who was one of two professors to oversee the project, says that can create problems for cellphone transmission towers, particularly in remote areas. Companies use cellphone repeaters to extend the range of networks, and often transmit and receive on different channels, but the new technology could be cheaper and more effective, the professor says, reducing cellphone dead zones.

The new technology, developed last winter and spring by Jung Il Choi, Mayank Jain, and Kannan Srinivasan, who were doctoral students at the time, uses strategically placed transmitters and receivers to cancel out the outgoing signals and allow incoming signals to be detected.

The three developed a radio that demonstrates the technology, known as full-duplex wireless, and presented their findings in September at the International Conference on Mobile Computing and Networking, or MobiCom. A Nokia researcher at the conference told Mr. Levis it was the best presentation he’d seen in three years.

The professor says improving cellphone service and improving the performance of wireless Internet routers are two of the many potential applications of the technology, which the students are continuing to refine. It’s difficult to say exactly what changes it will bring, he adds, because it represents such a major shift.

“It really breaks this fundamental assumption of how wireless works,” Mr. Levis says.

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