Invention could dramatically increase smartphone battery life

Posted by Kate Taylor

A new 'subconscious mode' for smartphones could increase battery life by as much as 54 percent for users on busy networks.

University of Michigan computer scientists say that as much as 80 percent of the time, idle phones are expending energy by searching for a clear communication channel. Their new approach, dubbed E-MiLi, or Energy-Minimizing Idle Listening, it designed to make them perform this idle listening more efficiently.

"My phone isn't sending or receiving anything right now, but it's listening to see if data is coming in so I can receive it right away," says professor Kang Shin.

"This idle listening often consumes as much power as actively sending and receiving messages all day."

E-MiLi works slows down the WiFi card's clock to up to one-sixteenth of its normal frequency, but jolts it back to full speed when the phone notices information coming in.

The hard part, says Shin, was getting the phone to recognize an incoming message while it was in this slower mode.

"We came up with a clever idea," Shin said. "Usually, messages come with a header, and we thought the phone could be enabled to detect this, as you can recognize that someone is calling your name even if you're 90 percent asleep."

When used with power-saving mode, the researchers found that E-MiLi can reduce energy consumption by around 44 percent for 92 percent of mobile devices in real-world wireless networks.

The problem is that, as well as new processor-slowing software on smartphones, E-MiLi would require new firmware for the phones and computers sending messages, allowing them to encode the message header in a new and detectable way.

WiFi chipset manufacturers would have to adopt the E-MiLi firmware modifications, and manufacturers would have to incorporate the chips into their products.

E-MiLi is, though, compatible with today's models, so that messages sent with devices using E-MiLi's encoding would still be received as usual on smartphones without E-MiLi.

E-MiLi can also be used with other wireless communication protocols that require idle listening, such as ZigBee.