"Subconscious Mode" Could Extend Your Smartphone's Battery Life
University of Michigan computer science and engineering professor Kang Shin and doctoral student Xinyu Zhang will present their new power management approach Sept. 21 at the ACM International Conference on Mobile Computing and Networking in Las Vegas. The approach is still in the proof-of-concept stage and is not yet commercially available, but we certainly know that demand for this kind of technology is out there. Who wouldn't take a few more hours of life on their smartphone?
Even when smartphones are in power-saving modes and not actively sending or receiving messages, they are still on alert for incoming information and they're searching for a clear communication channel. The researchers have found that this kind of energy-taxing "idle listening" is occurring during a large portion of the time phones spend in power-saving mode---as much as 80 percent on busy networks. Their new approach could make smartphones perform this idle listening more efficiently. It's called E-MiLi, which stands for Energy-Minimizing Idle Listening.
To find out how much time phones spend keeping one ear open, Shin and Zhang conducted an extensive trace-based analysis of real WiFi networks. They discovered that, depending on the amount of traffic in the network, devices in power-saving modes spend 60 to 80 percent of their time in idle listening. In previous work, they demonstrated that phones in idle listening mode expend roughly the same amount of power as they do when they're fully awake. According to UofM: Here's how E-MiLi works: It slows down the WiFi card's clock by up to 1/16 its normal frequency, but jolts it back to full speed when the phone notices information coming in. It's well known that you can slow a device's clock to save energy. The hard part, Shin said, was getting the phone to recognize an incoming message while it was in this slower mode.
When used with power-saving mode, the researchers found that E-MiLi is capable of reducing energy consumption by around 44 percent for 92 percent of mobile devices in real-world wireless networks.