Kari Jyrkkä

Observations on power-efficiency trends in mobile communication devices

Computing solutions used in mobile communications equipment are essentially the same as those in personal and mainframe computers. The key differences between the implementations are found at the chip level: in mobile devices low leakage silicon technology and lower clock frequency are used. So far, the improvements of the silicon processes in mobile phones have been exploited by software designers to increase functionality and to cut development time, while usage times, and energy efficiency, have been kept at levels that satisfy the customers. In this paper, we explain some of the observed developments.

Component-based development of DSP software for mobile communication terminals

Abstract DSP software development has been tied down by extreme computational requirements. Furthermore, the DSP development tools available today are less advanced than in other embedded software design. This has lead to DSP software architectures that have not taken into account future expansion needs. Therefore, DSP software architectures have been inherently closed. Now, as system complexity increases, this design methodology becomes more of a burden, since it does not support component-based DSP software development that requires open interfaces. In this paper, mobile-communications DSP software architectures are studied as cases, and key areas for improvements towards more open DSP software development are identified. Proposed solutions are judged against the limited resources of mobile communication terminals and the characteristics of communication DSPs.

Implementing energy efficient embedded multimedia

Multimedia processing in battery powered mobile communication devices is pushing their computing power requirements to the level of desktop computers. At the same time the energy dissipation limit stays at 3W that is the practical maximum to prevent the devices from becoming too hot to handle. In addition, several hours of active usage time should be provided on battery power. During the last ten years the active usage times of mobile communication devices have remained essentially the same regardless of big energy efficiency improvements at silicon level. The reasons can be traced to the design paradigms that are not explicitly targeted to creating energy efficient systems, but to facilitate implementing complex software solutions by large teams. Consequently, the hardware and software architectures, including the operating system principles, are the same for both mainframe computer system and current mobile phones. In this paper, we consider the observed developments against the needs of video processing in mobile communication devices and consider means of implementing energy efficient video codecs both in hardware and software. Although inflexible, monolithic video acceleration hardware is an attractive solution, while software based codecs are becoming increasingly difficult to implement in an energy efficient manner due to increasing system complexity. Approaches that combine both the flexibility of software and energy efficiency of hardware remain to be seen.