A wireless sensor network (WSN) consists of hundreds or thousands of sensor nodes organized in an ad hoc manner to achieve a predefined goal. Although WSNs have limitations in terms of memory and processors, the main constraint that makes WSNs different from traditional networks is the battery problem which limits the lifetime of a network. Different approaches are proposed in the literature for improving the network lifetime, including data aggregation, energy efficient routing schemes, and MAC protocols. Sink node mobility is also an effective approach for improving the network lifetime. In this paper, we investigate controlled sink node mobility and present a set of algorithms for deciding where and when to move a sink node to improve network lifetime. Moreover, we give a load-balanced topology construction algorithm as another component of our solution. We did extensive simulation experiments to evaluate the performance of the components of our mobility scheme and to compare our solution with static case and random movement strategy. The results show that our algorithms are effective in improving network lifetime and provide significantly better lifetime compared to static sink case and random movement strategy.

Sink mobility is one of the most effective solutions for improving lifetime and has been widely investigated for the last decade. Algorithms for single-sink mobility are not directly applied to the multiple-sink case due to the latter's specific challenges. Most of the approaches proposed in the literature use mathematical programming techniques to solve the multiple-sink mobility problem. However, doing so leads to higher complexities when traffic flow information for any possible sink-site combinations is included in the model. In this paper, we propose two algorithms that do not consider all possible sink-site combinations to determine migration points. We first present a centralized movement algorithm that uses an energy-cost matrix for a user-defined threshold number of combinations to coordinate multiple-sink movement. We also give a distributed algorithm that does not use any prior network information and has a low message exchange overhead. Our simulations show that the centralized algorithm gives better network lifetime performance compared to previously proposed MinDiff-RE, random movement, and static-sink algorithms. Our distributed algorithm has a lower network lifetime than centralized algorithms; sinks travel significantly less than in all the other schemes.

Moving the sink node is an effective solution for improving the lifetime of wireless sensor networks (WSN). Different methods in the literature schedule sink movements and determine sink stay points. This paper provides another insight to the sink mobility problem in WSNs by incorporating node-load parameters into a matrix and using this matrix to determine which sink site to visit in each round. We first present a packet-(traffic) load-based sink movement algorithm that relies on the packet distribution of nodes in each sink site for a given topology construction algorithm. We extend this algorithm by considering the distances the packets are transmitted, and in this manner obtain an energy-load-based algorithm. We also provide an integer programming (IP) model to compute optimal results. Our extensive simulations show that our energy-and packet-based algorithms significantly improve network lifetime compared to keeping the sink static or moving it randomly. Our energy-based algorithm can increase network lifetime by a factor of 2 compared to random movement and by a factor of 5 compared to keeping the sink static. It remains only around 5% behind the optimal solution.

Moving the sink node is an effective solution for improving the lifetime of wireless sensor networks (WSN). Different methods in the literature schedule sink movements and determine sink stay points. This paper provides another insight to the sink mobility problem in WSNs by incorporating node-load parameters into a matrix and using this matrix to determine which sink site to visit in each round. We first present a packet-(traffic) load-based sink movement algorithm that relies on the packet distribution of nodes in each sink site for a given topology construction algorithm. We extend this algorithm by considering the distances the packets are transmitted, and in this manner obtain an energy-load-based algorithm. We also provide an integer programming (IP) model to compute optimal results. Our extensive simulations show that our energy-and packet-based algorithms significantly improve network lifetime compared to keeping the sink static or moving it randomly. Our energy-based algorithm can increase network lifetime by a factor of 2 compared to random movement and by a factor of 5 compared to keeping the sink static. It remains only around 5% behind the optimal solution.