Bilkent University
Department of Computer Engineering
Ph.D Dissertation


Energy-Efficient Sink Mobility Algorithms for Wireless Sensor Networks


Metin Koç
PhD Candidate
(Supervisor: Assoc. Prof. Dr. İbrahim Körpeoğlu)
Computer Engineering Department
Bilkent University

A wireless sensor network consists of a large number of tiny sensor nodes which are capable of sensing an environment and sending the collected data to a sink node. For most scenarios, sensor nodes are powered with irreplaceable batteries and this dramatically limits the lifetime of the network, especially due to overloading of the sensor nodes neighboring sink node. Such nodes need to forward more traffic than other nodes in the network. Moving sink node and in this way distributing forwarding-load evenly among sensor nodes is one of the important techniques for improving lifetime of sensor networks. We propose different mobility algorithms for single-sink and multiple-sink mobility problem to efficiently move sink nodes through a predefined set of sink sites.

We first provide packet-load and energy-load based sink mobility algorithms, called PLMA and ELMA, in which node-load parameters are incorporated into a table and this table is used to determine which sink site to visit in each round. We also give an integer programming model to get optimal results and do benchmarking. Since routing topology is an important component of sink mobility schemes, we also propose centralized and distributed routing topology construction algorithms to further increase network lifetime. Additionally, we propose an adaptive energy-load based sink movement algorithm, called A-ELMA, which does not require an initial training phase to learn about network topology. It incrementally constructs and updates energy-load table each time it visits a site location.

Finally, besides proposing algorithms for single-sink mobility problem, we also propose two different algorithms for multiple-sink mobility problem. Our Multiple Sink Movement Algorithm (MSMA) is a centralized algorithm and effectively limits the sink site combinations to reduce computation and communication overhead in scheduling sink movements without harming network lifetime significantly. Our Prevent and Move Away (PMA) algorithm is a fully distributed algorithm and does not require topology information to be collected. It selects sites based on remaining energy values and distance metrics.

We evaluated our algorithms and compared them to some basic approaches in the literature by conducting extensive simulation experiments. Our simulation results show that our algorithms can perform better than some other alternatives in terms of network lifetime, latency and travel distance. We also identify under which conditions our algorithms perform better for each of these metrics. We observed that our algorithms provide simple-to-use, efficient, and effective solutions for single- and multiple-sink mobility problems in wireless sensor networks.


DATE: 2 September, 2015, Wednesday @ 9:30