Research On Event-driven Wireless Sensor Network Technology

Wireless sensor network (WSN), which is a composition of sensor, MEMS and networks technologies, is a brand-new technology about information acquiring and processing. Due to its flexibility, robustness and intelligence, it will be used in a variety of applications such as, military, environmental monitoring, health monitoring, home automation, structure health monitoring, traffic, space explorer, managing inventory control, airport and factory safety systems.Information gathering in sensor networks can follow different patterns, depending mostly on the specific needs of the applications. In the event-driven case seneors start communication with the sink only if sensing an event, i. e, a situation that is worth reporting. So that energy consumes is reduced.Sensors are tiny devices with sensing, processing, and transmitting capabilities; but have a limited energy supply. It is usually considered impossible or impractical (from a technical or economical point of view) to recharge their batteries. With the energy constrained nature of wireless sensors, it is utmost important to make efficient use of battery power in order to increase their lifetimes. The research is based on prolonging the lifetime of wireless sensor networks, and the main contents in this paper are as follows:Firstly, MAC protocol has utmost influence on energy consumption of networks is discussed. Power consumption of node sub systems and reasons of energy waste are analyzed, the properties of a well-defined MAC protocol are proposed. In this paper MAC protocols can be classified into three categories: contention-based, collision free, and hybrid schemes. Three classic MAC protocols (S-MAC, DMAC and SMACS/EAR) are chose and a simple description is given.Then, wireless sensor network simulator ns-2 is used to simulate S-MAC and DMAC. MAC protocol combine with routing protocol is considered, after several routing protocols (Real-time search, Constrained flooding, Sensor-driven and cost-aware ant routing) been discussed, three performance metrics (energy consumption, latency, success rate) are used to comparing the three protocols when they combine with CSMA MAC protocol.Finally, we propose an energy management scheme based on network architecture and optimal distribution of redundant sensor nodes in this paper, aiming at prolonging the lifetime of the event-driven wireless sensor networks. We divide the monitoring area into layered network architecture based on regular hexagonal cells (RHCs). The number of redundant sensor nodes with optimal distribution decreased from inner layers to outer layers. Simulation analysis is conducted on the network lifetime with different layers and different probability of burst events (ρ), and is compared with uniform distribution and Poisson distribution with the same number of sensor nodes. The numerical results show that our scheme can prolong network lifetime effectively.