Wifi turn-taking could double phone battery life

Posted by Kate Taylor

A Duke University graduate student has found a way to double the battery life of mobile devices with a small alteration to Wifi technology - and it all depends on cooperation.

Wifi's energy drain on devices is especially severe in the presence of others nearby, as each device has to 'stay awake' and wait for its turn to download.

For this reason, downloading a movie in Manhattan drains a battery far more than downloading the same movie in a farmhouse in the Midwest.

But the SleepWell system 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 for the competing devices as well.

The situation can be compared to the rush hour. If offices staggered their working hours, there would be less of a rush, giving more free time for all, but withour cutting the total number of hours worked.

"The same is true of mobile devices trying to access the Internet at the same time," says Justin Manweiler, a graduate student in computer science.

"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, he says, mobile devices will need to access the internet more frequently.

"Energy is certainly a key problem for the future of mobile devices, such as iPhones, iPads and Android smartphones," says Romit Roy Choudhury, assistant professor of electrical and computer engineering.

"The SleepWell system can certainly be an important upgrade to Wifi technology, especially in the light of increasing Wifi density."