Research On The Sink Node Movement Problem In Wireless Sensor Networks

With the rapid development of wireless and microelectronics-based technologies, wireless sensor networks become more and more mature. As a new generation of wireless networks, it effectively meets the increasingly complex scenarios with data collection requirement in a timely manner. Already there are wireless sensor networks as commercial products for specific applications, such as the indoor positioning system (Massachusetts Institute of Technology, MIT), field vehicle tracking system (University of Virginia) and Microsoft's Sensor Web system, and so on. Unlike underlay hardware system, software system of sensor network is still evolving with a high speed. Due to hardware design and demands of different application scenarios, sensor networks in general are quite different from other wireless networks such as Ad Hoc, Mesh. It has own signature difference, such as low cost, energy, and bandwidth requirements etc. How to give good solutions for the software aspect of the theory and practice remain hot spots for the research.Most of the previous literatures focus on the sensor nodes, which are energy-constrained. More specifically, they focus on how to use sensor redundancy to improve network efficiency and prolong the network life cycle. However, in the practical application of network these literatures have great limitations if they only focus on sensor nodes that have limited energy and communication ability. Because, in general, the purpose of sensor networks is to ensure the collection and transfer data to the outside world, therefore, how to complete this last step from wireless networks to wired networks is very important. In sensor networks, this role is known as data aggregation nodes (also sink nodes). Compared to sensor nodes, sink nodes are greatly enhanced in terms of battery power, communication ability and mobility. Naturally, we should shift our focus from sensors to sinks. Also there are previous literatures to follow.In this thesis, based on thorough analysis of the sensor network model, several optimization models have been introduced into the research field. Through thorough research on the previous literature in this area, numerous novel schemes are proposed to deal with different types of sink nodes. The main contributions of this thesis are as follows:1) Research and analysis of the sensor network structure, characteristics, key technologies, and the development of history.2) Detailed survey of previous research works on sinks nodes. Based on the assumption of mobility, they are divided into two categories: the sink nodes keep static after the deployment stage, namely the sink node placement problem; and the sink nodes are mobile during the running of the network, namely the sink node mobility problem. Detailed study and analysis are performed on two categories of design problems. 3) Study on the optimal placement problem in wireless sensor network. Main difficulty is to place the sink and the need for joint optimization of routing problem to obtain the optimal life cycle. For such difficulties, a countermeasure is proposed by discreting continuous search space. Theoretical proof is given. Based on this algorithm, a grid-based optimization model is developed, whose efficiency are verified by both theoretical analysis and experimental simulations.4) Study on the lifetime optimization problem in wireless sensor networks using mobile sink nodes. More specifically, address the problem of how to schedule sink nodes among different location candidates to maximize network lifetime based on a linear optimization model. The results show that the ability to use a mobile sink node has a significant impact on the network life cycle, confirming the conclusions of previous studies. It shows that even limited use of a mobile sink node will greatly enhance the lifetime, marking that this issue is of great research potential.