Communication-based power management - Design & Test of Computers, IEEE

significant and rapidly expanding segment of the electronics and semiconductor industries. Unfortunately, projections of the complexity, functionality, and performance of such systems far exceed expected improvements in battery technologies, leading to a widening “battery gap.”1,2 Bridging this gap is a challenge that system designers must face for the foreseeable future. The need to improve battery life has, in large part, driven the research and development of low-power design techniques for electronic circuits and systems.3 Low-power design successfully reduces the energy a system draws from the battery and hence improves battery life to some extent. However, truly maximizing battery life requires an understanding of both the energy source and the energy-consuming system. Research has shown that the amount of energy supplied by a battery varies significantly, depending on how the system draws the energy (the “Principles of battery discharge” sidebar explains the basics). Consequently, designers should develop battery-efficient, rather than merely energy-efficient, design techniques specifically tailored toward the characteristics and limitations imposed by battery-powered systems. Recent contributions to the area of batteryefficient system design include battery models that capture important electrochemical effects during battery discharge.4-7 These models estimate battery life and capacity under various discharge scenarios, and are a key part of a battery-driven design methodology. Techniques for designing battery-efficient systems include battery-driven frequency selection,8 voltage setting,9 task scheduling,10 and extensions to conventional power management.11 Researchers have proposed battery scheduling for multibattery systems to optimize a battery subsystem to best meet system power requirements.12,13 Groups are developing standards that improve interoperation of batteries and electronic systems (http://www.sbs-forum.org). Lahiri et al. provide a survey of battery models and batterydriven design techniques.2 Communication-based power management (CBPM) is a new battery-driven system-level power management methodology. It aims at improving battery life beyond what is achievable using state-of-the-art low-power design techniques.