Paek-MobiSys10 - Energy-Efficient Rate-Adaptive GPS-based...

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Unformatted text preview: Energy-Efficient Rate-Adaptive GPS-based Positioning for Smartphones ∗ Jeongyeup Paek Joongheon Kim Ramesh Govindan Embedded Networks Laboratory Computer Science Department University of Southern California {jpaek,joonghek,[email protected] ABSTRACT Many emerging smartphone applications require position informa- tion to provide location-based or context-aware services. In these applications, GPS is often preferred over its alternatives such as GSM/WiFi based positioning systems because it is known to be more accurate. However, GPS is extremely power hungry. Hence a common approach is to periodically duty-cycle GPS. However, GPS duty-cycling trades-off positioning accuracy for lower energy. A key requirement for such applications, then, is a positioning system that provides accurate position information while spending minimal energy. In this paper, we present RAPS, rate-adaptive positioning sys- tem for smartphone applications. It is based on the observation that GPS is generally less accurate in urban areas, so it suffices to turn on GPS only as often as necessary to achieve this accu- racy. RAPS uses a collection of techniques to cleverly determine when to turn on GPS. It uses the location-time history of the user to estimate user velocity and adaptively turn on GPS only if the estimated uncertainty in position exceeds the accuracy threshold. It also efficiently estimates user movement using a duty-cycled ac- celerometer, and utilizes Bluetooth communication to reduce po- sition uncertainty among neighboring devices. Finally, it employs celltower-RSS blacklisting to detect GPS unavailability (e.g., in- doors) and avoid turning on GPS in these cases. We evaluate RAPS through real-world experiments using a prototype implementation on a modern smartphone and show that it can increase phone life- times by more than a factor of 3.8 over an approach where GPS is always on. Categories and Subject Descriptors C.3 [ Special-purpose and Application-based Systems ]: Real-time and embedded systems ∗ This material is based upon work supported by the National Sci- ence Foundation under Grant Nos. 0121778 and 0905596. Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF). Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee....
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This note was uploaded on 08/25/2011 for the course EEL 6788 taught by Professor Boloni,l during the Spring '08 term at University of Central Florida.

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Paek-MobiSys10 - Energy-Efficient Rate-Adaptive GPS-based...

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