Closed-loop power-control governor for multimedia mobile devices

Abstract

The micro-electronics industry has been boosting the capabilities of multimedia mobile devices, but the battery, which is the only power source of most mobile devices, is experiencing relatively slow development. Therefore, determining how to optimize the energy consumption of mobile devices under a predefined performance requirement has become a critical issue. The video decoder, as one of the main energyconsuming multimedia applications, is the target application of this manuscript. This paper presents control algorithms for power regulation under the limited battery capacities of multimedia hand-held devices while executing a decoder application and maintaining a reasonable quality of user experience. A control system, which includes a real-time closedloop control subsystem and a power-control governor (PCG), has been implemented in the operating system of a low-cost development board. Instead of using any specific power sensor, a PMC (performance monitoring counter)-based estimator is used as the feedback signal in the closed-loop subsystem. After a theoretical system model has been obtained, classic controllers have been implemented in the development board. The control system is able to regulate the power consumption and the battery discharge rate in the presence of fluctuations in the decoder power-consumption demand. The proposed PCG can extend the battery lifetime by 15.5% and 12.8% in comparison with the conservative and ondemand governors of Linux, respectively.