Applied Soft Computing 34 (2015) 539–550 Contents lists available at ScienceDirect Applied Soft Computing j ourna l h o mepage: www.elsevier.com/locate/asoc Energy-efficient topology control algorithm for maximizing network lifetime in wireless sensor networks with mobile sink Huan Zhao a,b,∗ , Songtao Guo a,b,∗ , Xiaojian Wang a , Fei Wang b a College of Computer Science, Chongqing University, Chongqing 400044, PR China b College of Electronic and Information Engineering, Southwest University, Chongqing, 400714, PR China a r t i c l e i n f o Article history: Received 25 March 2013 Received in revised form 7 March 2015 Accepted 11 May 2015 Available online 27 May 2015 Keywords: Maximum lifetime Energy balancing Mobile sink Anchor nodes Topology control a b s t r a c t Uneven energy consumption is an inherent problem in wireless sensor networks characterized by multi- hop routing and many-to-one traffic pattern. Such unbalanced energy dissipation can significantly reduce network lifetime. In this paper, we study the problem of prolonging network lifetime in large-scale wire- less sensor networks where a mobile sink gathers data periodically along the predefined path and each sensor node uploads its data to the mobile sink over a multi-hop communication path. By using greedy policy and dynamic programming, we propose a heuristic topology control algorithm with time complex- ity O(n(m + n log n)), where n and m are the number of nodes and edges in the network, respectively, and further discuss how to refine our algorithm to satisfy practical requirements such as distributed comput- ing and transmission timeliness. Theoretical analysis and experimental results show that our algorithm is superior to several earlier algorithms for extending network lifetime. © 2015 Elsevier B.V. All rights reserved. 1. Introduction In recent years, mobile data gathering by deploying a mobile sink in wireless sensor networks (WSNs) has attracted much inter- ests from researchers [1]. A WSN is a multi-hop wireless ad hoc network with hundreds or thousands of unattended sensors. Since most sensor nodes are powered by limited disposable batteries, the energy consumption becomes one critical constraint in WSNs. The mobile sink could be a mobile robot or a vehicle equipped with powerful transceiver, battery, and large memory. The purpose of deploying the mobile sink is to reduce the communication expense among sensor nodes. In large-scale WSNs, to ensure that the sensed data are delivered to the base station in time, the mobile sink could not move nearby every sensor node and collect data one by one, thus only sensors that are deployed near the mobile sink’s tra- jectory can directly send data to the mobile sink and other nodes should transmit their data to the mobile sink in a multi-hop man- ner, as shown in Fig. 1. This results in highly nonuniform energy usage among sensors. The energy of the sensors near the trajec- tory is depleted much faster than that of others since these sensors need to relay much more packets for the sensors far away from the ∗ Corresponding authors at: College of Computer Science, Chongqing University, Chongqing 400044, PR China. Tel.: +86 23 65103199; fax: +86 23 65111874. E-mail addresses: zhaohuan@cqu.edu.cn (H. Zhao), guosongtao@cqu.edu.cn (S. Guo), cqwxj@hotmail.com (X. Wang), wangfei@cqu.edu.cn (F. Wang). trajectory. As a result, after these sensors fail, the network becomes disconnected even though most sensors still have plenty of energy. Based on those observations, we focus on how to prolong net- work lifetime in large-scale WSNs with mobile sink. We adopt the definition of network lifetime as the time until the first node exhausts its energy, which has been widely used. We assume that the trajectory is pre-determined by the algorithms [2,3] or it is fixed due to environmental restriction. Comparing with prolong- ing network lifetime in WSNs with static sinks, the problem of maximizing network lifetime in WSNs with mobile sink has its particular difficulties: (1) The trajectory may be irregular and the nodes which take charge of forwarding data to the mobile sink may be far away from each other, thus the corona-based algorithms such as EBDG [4] are infeasible. (2) Lack of central node increases the difficulty of coordination among sensor nodes, especially for the design of distributed algorithms. In this paper, we consider taking advantage of topology con- trol to select forwarding path and transmission power for each sensor node. The key idea of topology control is that, instead of transmitting with the maximal power, the nodes in a wireless multi-hop network collaboratively determine their transmission powers and define the network topology by forming the proper http://dx.doi.org/10.1016/j.asoc.2015.05.014 1568-4946/© 2015 Elsevier B.V. All rights reserved.