Paper #3: Low Power Techniques for an Android Based Phone

The document opens up with a definition of Android: a "software stack, which includes Linux kernel as underlying operating system, middleware software such as application frameworks and libraries and the some of the applications specific to mobile platform." The importance of this definition is to highlight the fact that the linux kernel is responsible for OS related management such as power control.

According to the author, there are 3 main power management categories to be considered:
a- Static Power Management: when the user is not interacting with the device
b- Active Power Management: power saving during short idle periods
c- Android Power Management: power management specific for android

The first solution discussed is related to active power management. The researchers looked at reducing the sampling rate of the OS. To do this they created a daemon process that would calculate system workload and perform frequency scaling depending on the requirements.

To work around the static power management the authors of the document decided to include modifications to the debug file system. These modifications targeted suspending and  resuming the system, as well as data retention during long idle periods.

For the last part it is important to understand the wake_lock. This mechanism keeps Andriod from going into suspend mode, and is kept running for as long as CPU usage is needed. For an application to run, it needs to acquire the wake_lock. The researchers recommend Android developers to look at the different types of wake_lock and use the lowest one possible for the context of their application. This way the application would avoid waiting for Android automatic timeouts when the application is not being used.