Snoozing boosts mobile battery life

DUKE (US) — Popular belief has it that taking a nap re-energizes our batteries. New research finds it could work for smartphones too.

Currently, WiFi’s wireless technology allows users to download information like pictures, music, and video from the Internet, but can be a major drain of battery, especially in the presence of other WiFi devices.

In such cases, each device has to “stay awake” before it gets its turn to download a small piece of the desired information. This means that the battery drainage in downloading a movie in Manhattan, for example, is far higher than downloading the same movie in a farmhouse in the Midwest.

New software, dubbed Sleepwell, eliminates this problem by allowing mobile devices to sleep while a neighboring device is downloading information—not only saving energy for the sleeping device, but also for competing ones.

“Big cities face heavy rush hours as workers come and leave their jobs at similar times,” says Justin Manweiler, a graduate student in computer science working with Romit Roy Choudhury, assistant professor of electrical and computer engineering at Duke University.

“If work schedules were more flexible, different companies could stagger their office hours to reduce the rush. With less of a rush, there would be more free time for all, and yet, the total number of working hours would remain the same. The same is true of mobile devices trying to access the Internet at the same time.

“The SleepWell-enabled WiFi access points can stagger their activity cycles to minimally overlap with others, ultimately resulting in promising energy gains with negligible loss of performance.”

With cloud computing on the horizon, mobile devices will need to access the Internet more frequently, but such frequent access could be severely constrained by the energy toll that WiFi takes on the device’s battery life, says Roy Choudhury.

“Energy is certainly a key problem for the future of mobile devices, such as iPhones, iPads, and Android smartphones. The SleepWell system can certainly be an important upgrade to WiFi technology, especially in the light of increasing WiFi density.”

The research is supported in part by the National Science Foundation.

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