Duke's SleepWell Software Doubles Cell Phone Battery Life

Last week at the 9^th Association for Computing Machinery’s International Conference on Mobile Systems, Applications and Services (MobiSys 2011), held in Washington, D.C., researchers from Duke University presented techniques to double the battery life of mobile devices, such as smartphones or laptop computers. Duke graduate student Justin Manweiler has developed software that teaches cell phones to take turns when sharing bandwidth.

According to the researchers, Wi-Fi is a popular wireless technology that helps users download information from the Internet. However, downloading pictures, music and video streaming can be a major drain of battery. The energy drain is especially severe in the presence of other Wi-Fi devices in the neighborhood.  In such cases, each device has to “stay awake” before it gets its turn to download a small piece of the desired information, the researchers said. This means that the battery drainage in downloading a movie in Manhattan is far higher than downloading the same movie in a farmhouse in the Midwest, the researchers added.

The Duke-developed software eliminates this problem by allowing mobile devices to sleep while a neighboring device is downloading information. This not only saves energy for the sleeping device, but also for competing devices as well. The new system has been termed SleepWell by Manweiler, a graduate student in computer science under the direction of Romit Roy Choudhury, assistant professor of electrical and computer engineering at Duke’s Pratt School of Engineering.

Manweiler described the system by analogy: “Big cities face heavy rush hours as workers come and leave their jobs at similar times. 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,” Manweiler added. “The SleepWell-enabled Wi-Fi access points can stagger their activity cycles to minimally overlap with others, ultimately resulting in promising energy gains with negligible loss of performance,” noted Manweiler.

With cloud computing on the horizon, mobile devices will need to access the Internet more frequently – however, such frequent access could be severely constrained by the energy toll that Wi-Fi takes on the device’s battery life, according to Roy Choudhury.

“Energy is certainly a key problem for the future of mobile devices, such as iPhones, iPads and Android (News - Alert) smartphones,” stated Choudhury. “The SleepWell system can certainly be an important upgrade to Wi-Fi technology, especially in the light of increasing Wi-Fi density.”

Choudhury’s research team, known as the Systems Networking Research Group, is supported by the National Science Foundation, as well as companies such as Microsoft Research, Cisco, Nokia (News - Alert) and Verizon.

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