New software to extend smartphone battery life

Researchers, including those of Indian-origin, have developed a software that can significantly reduce the battery drainage in smartphones by intelligently suppressing apps that run in the background.
Researchers at Purdue University, Intel Corp and startup company Mobile Enerlytics studied the use of 2,000 smartphones 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 at Purdue University.
Out of the 45.9 per cent of daily battery drain where the screen is off, 28.9 per cent is due to apps that frequently wake up and run in the background, the researchers said.

Out of this 28.9 per cent, researchers have shown how to save 15.7 per cent with a new system called HUSH.
"During screen-off, the phone hardware should enter the sleep state, draining close to zero power," Hu said.

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

"Being able to reduce the total daily energy drain by about 16 per cent is rather significant because you can extend the battery charge by one-sixth," Hu said.
The key insight behind the proposed solution, 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.

When the phone is in screen-off, it also continues draining power for various legitimate maintenance purposes - for example, A WiFi beacon, when the phone's WiFi system sends a periodic signal to the access point once every 200 milliseconds, and a "cellular paging" function, when the phone talks to the base station every 1.28 seconds to check for incoming calls or data.
In efforts to extend battery life, researchers will work to reduce energy drain from these legitimate functions as well as faulty apps.