New tool shuts non-useful apps to cut energy drain

Do you know that apps drain nearly 29 percent of battery power while the smartphone screen is off? To address the problem, researchers including three of Indian-origin have created a software tool that reduces the energy drain by about 16 percent.

Researchers at Purdue University, Intel Corporation and startup company Mobile Enerlytics studied the use of 2,000 Samsung Galaxy S3 and S4 phones served by 191 mobile operators in 61 countries.

"This was the first large-scale study of smartphone energy drain 'in the wild' or in everyday use by consumers," said Y Charlie Hu, professor of electrical and computer engineering at Purdue in a statement.

The research paper was authored by Hu, Purdue graduate students Xiaomeng Chen, Abhilash Jindal and Ning Ding and Intel researchers Maruti Gupta and Rath Vannithamby.

Out of the 45.9 percent of daily battery drain where the screen is off, 28.9 percent is due to apps that frequently wake up and run in the background.

Out of this 28.9 percent, the team has shown how to save 15.7 percent with a new system called HUSH.

The key insight behind HUSH is that background activities of individual apps are not equally important to individual smartphone users.

For example, frequent Facebook updates during screen-off may be useful to a user who checks Facebook feeds and reacts to notifications often but they are much less useful to another user who rarely checks such updates.

The HUSH system dynamically identifies app background activities that are not useful to the user experience on a per-app basis and suppresses such background app activities during screen-off to reduce the battery drain.

During screen-off, the phone hardware should enter the sleep state, draining close to zero power.

Apps wake the phone up periodically during screen-off to do useful things, but then afterward, they should let the phone go back to sleep.

"They are not letting the phone go back to sleep because of software bugs and, specifically, due to the incorrect use of Android power control application programming interfaces called wakelocks," Hu noted.

Being able to reduce the total daily energy drain by about 16 percent is rather significant because you can extend the battery charge by one-sixth.

"The big picture is that we want to double the battery life for smartphones," the team concluded.

Researchers presented their findings this week at the "ACM MobiCom 2015" conference in Paris.