Research On Some Energy Saving Technologies For Wireless Sensor Networks

A wireless sensor network(WSN) consists of spatially distributed autonomous sensor nodes to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants. Wireless sensor networks are different from traditional networks especially in their hardware constrains including the CPU and memory capacities, the wireless transmission capacities, and the power supplies. So it's a long term hot topic for researchers to find ways on how to utilize the system capacities of WSN nodes efficiently, among which energy efficiency, that is energy saving issue, is one of the hottest topics.In this dissertation, we focus our interests on the energy saving issues concerning WSN operating system and the network construction.The major works of this dissertation are as follows:(1) Research on node operating sytem for wireless sensor networks. An operation system, named TaraxOS, for wireless sensor networks is proposed. The functions of the TaraxOS such as interrupt processing, memory management and task scheduling are analyzed and implemented. After introducing the node's working flow, the performances of the TaraxOS are analyzed and some limitations of the scheduling mechanism are discussed. Then a battery model based low energy periodic task scheduling algorithm is suggested and its effectiveness is proved by simulation. The simulation results show that TaraxOS has the the most desirable characteristics as smaller size when compared with TinyOS, low power consumption also compared with TinyOS, and robustness.(2) In order to improve energy efficiency and to prolong lifetime of wireless sensor networks, a new distributed algorithm called EMISB for computing minimum connected dominating set based on node's discrete Markov chain model is proposed. A Markov model for dominating node and dominated nodes, which is used to predict the nodes'energy consumption, is developed. The dominating nodes act as cluster head nodes in the network. The algorithm runs multi-rounds with the election of the dominating nodes based on nodes'degree and the energy remained in the beginning of every round, and the time this round will last is computed. After this round, the network will re-elect dominating nodes and run the next round. Simulation results show that the new algorithm can prolong the lifetime of the network evidently by balancing energy consumption and increasing energy efficiency.(3) In order to improve the efficiency of broadcasting and to reduce energy consumption, 1-hop neighbor transmission coverage information based distributed algorithm, which is called OHDC, for connected dominating set is proposed. 1-hop neighbor node transmission coverage information is used to calculate the minimum forwarding set in a distributed way on each node of the network, and then a method of broadcasting information of minimal forwarding set is used to construct a connected dominating set. 1-hop neighbor transmission coverage information based distributed algorithm for connected dominating set is designed to get a small connected dominating set, while minimizing the consumption of energy and time. The simulation results show that the algorithm has achieved its purpose of fast convergence, low transmission traffic and while a reasonable connected dominating set is figured out.(4) A distributed algorithm called DBC for virtual backbone on which routing can be built with cellular structure in WSN is proposed in this dissertation which resolves the distort problem to some extent in cellular structure used in ABP[95]. The simulation results show that the algorithm has constructed a virtual backbone with fewer nodes than ABP, and is less affected by the node density.