A Power Management Model for Android Operated Smart Phones

Abstract

Power management (PM) of smartphones has evolved since the introduction of Advanced Power Management (APM) and Advanced Configuration & Power Interface (ACPI). These are primarily aimed at personal computers. Although Android is based on Linux kernel, Android has put forward its own power management system during Google I/O 2011, it was reported that 400,000 Android devices are being activated per day and the proper power management of these devices is becoming an issue [2]. With more sophisticated hardware components being available on the smartphones and the tablets, the developers are exploiting them to provide state-of-the-art user experience. This comes at the cost of high drain of battery. It is studied that Wi-Fi, GPS, colourful bright display of Organic LED (OLED) and some uncontrollable background running applications consume very high power. Another study shows that the third-party advertisements shown in free Android apps consume up to 30% of the total power consumed by the app. Therefore, prolonged use of these hardware components and free apps displaying advertisements will increase the power dissipation and battery life will be reduced considerably [3]. Android employs an aggressive policy for power saving using wake locks but that is not sufficient to conserve the battery lifetime. Thus, developers wrote many power saving apps which are available in Google Play Apps store (previously known as Android market). To understand the operating principle, several of these apps are studied in depth. It is found that they aim at controlling different smartphone features like Wi-Fi, 2G and 3G connections, brightness level, CPU frequency, GPS and more to prolong the battery life. Historically, power management techniques rely on the ability of certain components to be turned on and off dynamically, thus enabling the system as a whole to save energy when those components are not being used. Only more recently, techniques have been introduced to enable some components to operate at different energy levels along the time. Multiple operational modes and Dynamic Voltage Scaling (DVS) are examples of such techniques that are becoming commonplace for microprocessors. Unfortunately, microprocessors are seldom the main energy drain in embedded systems so traditional on/off mechanisms are still of great interest.