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Cellphones Team ­p to Make Wi-Fi Where You Want It

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Scientists at Microsoft Research India and colleagues at the University of California, Santa Barbara have developed Cool-Tether, a system that combines the Internet connections of several smartphones to create high-speed wireless hotspots. Computers can connect to the phones using short-range Wi-Fi and request Web pages just like using a wireless router with a normal connection to the Internet.

Cool-Tether manages the smartphones' wireless connections, which can quickly drain batteries, to make the system practical. A previous version of the system used as many connections as possible from nearby phones to maximize a computer's Internet connection speed, but the heavy power overhead Wi-Fi places on mobile devices limited the system's usefulness. The researchers say Cool-Tether is the first energy-aware technique for creating on-the-fly hotspots through cell phones.

"Instead of blindly using all the available phones, Cool-Tether determines the optimal number of phones to use to send the contents of the Web page," says Microsoft Research India computer scientist Vishnu Navda. Every time a phone transfers a piece of data by Wi-Fi to a computer, it "lingers in [a] high-power active state for a few seconds" no matter how much data was transferred, Navda says, which drains a phone's battery quickly. Cool-Tether solves this problem by coordinating the phones to send data in fewer, longer bursts, and to make sure that each "energy tail" is associated with as much data transfer as possible.

Cool-Tether uses a quarter of the energy as the previous version of the system, with little loss in download speeds.

From New Scientist
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