A Case Study of a System-Level Approach to Power-Aware Computing THOMAS L. MARTIN Virginia Tech, Blacksburg and DANIEL P. SIEWIOREK, ASIM SMAILAGIC, MATTHEW BOSWORTH, MATTHEW ETTUS, and JOLIN WARREN Carnegie Mellon University, Pittsburgh This paper introduces a systematic approach to power awareness in mobile, handheld computers. It describes experimental evaluations of several techniques for improving the energy efficiency of a system, ranging from the network level down to the physical level of the battery. At the network level, a new routing method based upon the power consumed by the network subsystem is shown to improve power consumption by 15% on average and to reduce latency by 75% over methods that consider only the transmitted power. At the boundary between the network and the processor levels, the paper presents the problem of local versus remote processing and derives a figure of merit for determining whether a computation should be completed locally or remotely, one that involves the relative performance of the local and remote system, the transmission bandwidth and power consumption, and the network congestion. At the processor level, the main memory bandwidth is shown to have a significant effect on the relationship between performance and CPU frequency, which in turn determines the energy savings of dynamic CPU speed-setting. The results show that accounting for the main memory bandwidth using Amdahl’s law permits the performance speed-up and peak power versus the CPU frequency to be estimated to within 5%. The paper concludes with a technique for mitigating the loss of battery energy capacity with large peak currents, showing an improvement of up to 10% in battery life, albeit at some cost to the size and weight of the system. Categories and Subject Descriptors: C.4 [Computer Systems Organization]: Performance of Systems—Design studies; Modeling techniques; Performance attributes; C.2.1 [Computer Com- munication Networks]: Network Architecture and Design—Wireless communications; C.5.3 [Computer System Implementation]: Microcomputers—Portable devices General Terms: Design, Experimentation, Measurement, Performance Additional Key Words and Phrases: Power-aware, energy-aware, battery properties, dynamic power management, handheld computers, multihop wireless network The work reported here was supported by the National Science Foundation under contract NSF- EIA-9901321 and DARPA under contract 660019928918 N306A. Authors’ addresses: T. Martin, Bradley Department of Electrical and Computer Engineering, Virginia Tech, 340 Whittemore Hall (0111), Blacksburg, VA 24061; email: tlmartin@vt.edu; D. Siewiorek, A. Smailagic, M. Bosworth, M. Ettus, and J. Warren, Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213. Permission to make digital/hard copy of all or part of this material without fee for personal or classroom use provided that the copies are not made or distributed for profit or commercial advan- tage, the ACM copyright/server notice, the title of the publication, and its date appear, and notice is given that copying is by permission of the ACM, Inc. To copy otherwise, to republish, to post on servers, or to redistribute to lists requires prior specific permission and/or a fee. C  2003 ACM 1539-9087/03/0800-0255 $5.00 ACM Transactions on Embedded Computing Systems, Vol. 2, No. 3, August 2003, Pages 255–276.