Real-time power-consumption control system for multimedia mobile devices

Energy consumption in battery operated mobile devices is a critical issue. Autonomy periods are increasingly compromised as the complexity of tasks, such as the widespread video decoding ones, is also increased. While new higher-capacity batteries are being developed, techniques to control, i.e. save, the energy consumption can provide a significant benefit. This paper presents the proposal, implementation and test of a real-time closed-loop control system applicable to the power-consumption regulation of multimedia mobile devices. The novel closed loop does not need any specific power sensor but only standard performance monitoring counters (PMCs) available in common mobile processors. From them, the power consumption is estimated with an algorithm to be included into the operating system, along with the control system itself. A theoretical system model has been first developed to (1) enable the design of some controllers and (2) validate the actual results obtained from the control system prototype into a given low-cost development board. These results prove the control-system stability and the comparative suitability of classic controllers to keep the multimedia-system consumption close to the desired value in steady state with settling times as short as a single sample interval.