Lin-MobiSys10 - Energy-Accuracy Trade-off for Continuous...

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Energy-Accuracy Trade-off for Continuous Mobile Device Location Kaisen Lin University of California San Diego La Jolla, CA, USA Aman Kansal, Dimitrios Lymberopoulos, and Feng Zhao Microsoft Research Redmond, WA, USA {kansal,dlymper,zhao} ABSTRACT Mobile applications often need location data, to update locally rel- evant information and adapt the device context. While most smart- phones do include a GPS receiver, its frequent use is restricted due to high battery drain. We design and prototype an adaptive location service for mobile devices, a-Loc, that helps reduce this battery drain. Our design is based on the observation that the required lo- cation accuracy varies with location, and hence lower energy and lower accuracy localization methods, such as those based on WiFi and cell-tower triangulation, can sometimes be used. Our method automatically determines the dynamic accuracy requirement for mobile search-based applications. As the user moves, both the accuracy requirements and the location sensor errors change. A- Loc continually tunes the energy expenditure to meet the chang- ing accuracy requirements using the available sensors. A Bayesian estimation framework is used to model user location and sensor errors. Experiments are performed with Android G1 and AT&T Tilt phones, on paths that include outdoor and indoor locations, us- ing war-driving data from Google and Microsoft. The experiments show that a-Loc not only provides significant energy savings, but also improves the accuracy achieved, because it uses multiple sen- sors. Categories and Subject Descriptors G.3 [ Probability and Statistics ]: Probabilistic Algorithms; C.2.4 [ Computer-Communication Networks ]: Distributed Systems— Distributed Applications General Terms Algorithms, Design, Measurement, Experimentation 1. INTRODUCTION Mobile applications often need location information and a large number of methods for mobile device localization have been devel- oped [23]. With GPS receivers becoming increasingly common- place in mobile phones and the widespread availability of WiFi and cell-tower signature based location services from Google [9] 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. MobiSys’10, June 15–18, 2010, San Francisco, California, USA. Copyright 2010 ACM 978-1-60558-985-5/10/06 . ..$10.00. and other providers, such location information is now becoming a reality. However, mobile applications still cannot assume con- tinuous and ubiquitous location access in their design because of the high energy expense of using the location sensors such as GPS receivers [12]. The variability in accuracy provided by various lo- cation sensors and the limits on their coverage areas pose addi- tional challenges for application developers. Using multiple loca-
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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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Lin-MobiSys10 - Energy-Accuracy Trade-off for Continuous...

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