Networks of light build on cellphone tech
Published: 27 Nov 2002 16:57 GMT
The University of California at Davis announced this week it has received a grant from the Defense Department to build a new generation of mobile phones that transmit and receive optical signals.
The optical mobile phones could make wireless communications speedier and more secure than existing optical fibre networks, researchers said.
U.C. Davis will share the $5m, four-year grant from the Defense Advanced Research Projects Agency (DARPA) with the Lawrence Livermore National Laboratory.
The researchers hope to build chip-sized devices that use a technology standard already in some mobile phones. That technology, called Code Division Multiple Access (CDMA), transmits and receives optical signals. CDMA, which runs about 20 percent of the world's wireless networks, is a proprietary standard. Qualcomm owns the patents.
A different technology in widespread use employs a method called wavelength division multiplexing, in which each cell phone uses a different wavelength of light, according to the researchers. In contrast, optical CDMA would encode each pulse, or bit of information, across a segment of wavelengths. The receiver uses a key to decode the signal and recreate the original pulse.
"Security-wise, there are strong advantages to optical CDMA because you can change the code at any time," U.C. Davis electrical engineer Zhi Ding said.
Some mobile phone systems, such as those from Sprint PCS and Verizon Communications, already use a type of CDMA for radio waves, according to the researchers.
The optical CDMA project is part of the California Institute for Information Technology Research in the Interests of Society (CITRIS), which is a coalition of U.C. campuses and industry partners. The organisation's goal is to apply technology to aid in emergency response, natural disasters and environmental monitoring.
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