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International Journal of Distributed Sensor Networks
Volume 2012 (2012), Article ID 947251, 10 pages
http://dx.doi.org/10.1155/2012/947251
Research Article

Time-Independent Data Collection Protocol in Mobility-Assistant Wireless Sensor Networks with Duty Cycles

Xiwei Zhang,1,2,3 Lijie Xu,1,2 and Guihai Chen1,2

1Department of Computer Science, Nanjing University, Nanjing 210000, China
2State Key Laboratory for Novel Software Technology, Nanjing University, Nanjing 210000, China
3Department of Computer and Information, Hohai University, Nanjing 210000, China

Received 16 December 2011; Accepted 26 February 2012

Academic Editor: Mo Li

Copyright © 2012 Xiwei Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Mobility-assistant sensor networks comprise mobile elements, and static sensors are established for the purpose of solving the serious problems such as overlapping or energy holes in wireless sensor networks (WSNs). In such systems, most of the energy is consumed when the radios are on, waiting for a mobile sink (MS) to arrive. Sleep/wake scheduling is an effective mechanism to prolong the lifetime of these energy-constrained wireless sensors. However, sleep/wake scheduling could result in substantial discovery delays because the sensor needs time to receive the beacon-ID signals when MS entered its communication range. In this paper, we first study on the MS discovery mechanism and the factors which affect the efficiency of data collection. Based on these results, we then provide a solution to the control problem of how to optimally adjust the system parameters of the sleep/wake scheduling protocol to maximize the network lifetime, subject to a constraint on the expected residual contact time. Our numerical results indicate that the proposed solution can balance the network consumption, especially in sparse sensor networks.