Research On Energy-Efficient Technologies In Wireless Sensor Network Based On S-MAC

Wireless Sensor Network (WSN) is composed of a large number of sensors which have functions of data sensing, gathering, handling and communicating. As energy constraint in sensor nodes is one of the important characteristics of WSN, a critical design issue for the MAC protocol of WSN is to efficiently reduce energy consumption. Based on the typical medium access control protocol, Sensor MAC (S-MAC), this thesis analyses the energy-saving mechanisms in MAC protocols and proposes two energy efficient MAC protocols.First of all, we introduce the typical MAC protocols in WSN and their energy-saving mechanisms. Then a detailed introduction to S-MAC is given, which is mainly designed for WSN. We discuss the energy-saving mechanisms and the details in energy consumption of S-MAC, and point out the problems existed in S-MAC. Secondly, Power Control Message Passing SMAC (PCMP-SMAC) is proposed to achieve the goal of energy saving. The fragments are transmitted continuously after being marked with"Fragment Indicator". Meanwhile, power control mechanism is introduced with collision prevention that allows nodes to vary their transmission power levels. The network simulation platform is established by NS-2 and simulation results show that PCMP-SMAC reduces energy consumption. Then, based on the characteristic of event driven WSN, a cross-layer Event-Driven Sensor MAC protocol (ED-SMAC) is proposed. ED-SMAC defines two network statuses: regular status and event status. On regular status, the basic techniques in S-MAC protocol are adopted. On event status, a new event-based cluster formation algorithm is proposed according to the cross-layer theory. Simulation results show that the proposed protocol saves node energy, shortens average packet latency, and improves event detection reliability.