A Research Of Sleep Scheduling Algorithm In Wireless Sensor Network

Wireless sensor network(WSN) consists of many cheap micro sensor nodes which are deployed in the monitoring area and form a self-organization and multi-hop network through wireless channel. Because of wide application such as be applied to battle, environmental surveillance, medical treatment and so on. But, sensor node has limited hardware resources and works from battery. So sensor nodes can not work for a long time. Moreover, nodes are always deployed in battle or unmanned area where the replacement of batteries or charging is difficult. Therefore, limited energy is the main problem of stopping the wireless sensor network’s large-scale actual deployment and the key problem is how to minimize energy consumption and extend network lifetime without sacrificing the Quality of Service.However, there is no strict control center in WSN and all the sensor nodes have the same status, that is to say WSN is an equal wireless communication network. So, there is no need that all the nodes work in the same time. Moreover, WSN always deploys a lot of nodes in the monitoring area. The great amount of nodes means that there are a lot of redundant nodes, which will lead to a lot of redundant data and collision in wireless channel. If redundant sensor nodes can be turned off when they have no sensing or relaying work to do, which can be called sleep scheduling, redundant data and collision in wireless channel can be reduced extremely and the lifetime of the whole network can be prolonged correspondingly.In this dissertation, we study on the sleep scheduling algorithm and research actuality of wireless sensor networks. Taking into account some classical sleep scheduling algorithm, we propose a virtual square grid-based coverage algorithm of sleeping scheduling for wireless sensor network (VSGCA). VSGCA consists of two parts.1. Redundant node eligibility rule. The basic idea of this algorithm is that the sensing area of each sensor node is divided into square grids. Whether the target node is a redundant node is equivalent to checking whether all the grids’centers are covered by its neighbors. From the theoretical proofs, VSGCA can guarantee that the monitoring area is covered by sensors fully. And the time complexity of redundant node eligibility is O(n X M), space complexity is O(n+M), where M denotes the number of grid points in each sensor node and n denotes the number of neighbor nodes. The computational complexity of VSGCA is less than most of other algorithms, especially in the high density network.2. Nodes chosen scheme based on current energy. To guarantee all the redundant nodes could not turn off in the same time, redundant nodes generate a random back-off time before they get into sleep. The back-off time is related to node’s current energy. That is to say, the more the node’s current energy is, the more back-off time is. The chosen scheme guarantee not only the area is covered fully, but also the network loads balancing.Simulations are carried out in NS-2.34. The simulation results show that this VSGCA could guarantee the monitoring area is covered by sensors fully, and in the aspect of average coverage degree, the number of active nodes, and network lifetime, VSGCA is close to CCP, EPRC and better than Ottawa, in the aspect of time and space complexity, VSGCA is close to Ottawa and better than CCP, EPRC.