Shrinking wireless base-stations

Researchers at Lucent Technologies’ Bell Labs have created the first all-silicon chips for the part of wireless networks that receives radio signals from mobile handsets.

The development, which was announced at the International Solid-State Circuits Conference, could reduce the size and cost of wireless base stations and could also provide network operators with more installation options.

Radio receivers in base stations contain 10 to 20 chips comprised of gallium arsenide, which is said to be a substantially more expensive semiconducting material than silicon, yet is needed to satisfy the requirements of a wireless network.

For instance, the radio receiver must handle many weak signals simultaneously, then amplify and filter them before further signal processing occurs.

‘Only recently have circuit designers made silicon chips for radios that rival the performance of gallium arsenide,’ said Bell Labs researcher Jenshan Lin. ‘Our silicon-based radio receiver is the first of its kind.’

Lin and his colleagues, Olga Boric-Lubecke and Penny Gould, created a radio receiver comprised of only three silicon, which is 100 times smaller than the gallium arsenide-based radio. The silicon chips also are 10 to 100 times less expensive to manufacture.

‘Because base stations with a silicon-based receiver would be smaller, service providers would have greater flexibility when installing them,’ said Boric-Lubecke. ‘For instance, the base stations could be placed in less obtrusive locations, such as behind billboards or on top of utility poles. This might help speed the deployment of the mobile Internet as it continues to grow.’

The all-silicon fabrication approach may also lead to the combination of a base-station radio receiver and digital signal processor on a single chip. ‘This would further reduce the base-station cost and move closer to creating a system-on-a-chip solution for base-station radio receivers,’ said Gould.

The Bell Labs silicon-based radio receiver could be used for all major mobile wireless standards, as well as future third-generation (3G) standards.

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