Design Of Highly Reriable Asynchronous Broadcast Mac Protocol For Wireless Sensor Networks

Wireless sensor network is a multi-hop and self-organized network through wireless communication which is composed of massive sensor nodes deployed in monitoring region in order to cooperatively sense, collect and process information. Reliability of WSN relies on reliability of each sendor node, unbalanced load results in rapid decline of nodes'energy, pulling down the reliability of WSN. When on broadcast mode, low ducy cycle leads to unsynchronized wakeup, resulting in abundant transmission and increased energy consumption.Efficient Multi-hop Broadcast Asynchronous Protocol is designed for Asynchronous WSN to support multi-hop broadcast. Thus the HR-MM broadcast protocol, a new load balanced and hop-count reduced MAC protocol designed for data broadcasting is designed. The improved MAC protocol use adaptive algorithm for dynamic message forwarding based on received wake-up messages'serial ID and multiple metrics including residual power and link quality. The ID is used to record the progress of broadcast and making forwarding decision. Thus broadcast forwarding ratio and hop count are decreased in a way, and lifetime of network is prolonged, average energy consumption is decreased and reliability of WSN is increased.Performance of improved MAC is showed through NS2 simulation and compared to high performance EMBA protocol, the outstanding asynchronous broadcast MAC protocol. The simulation results show that improved MAC protocol not only sharply improves network lifetime by 19.4% but also obviously reduces re-broadcast ratio no less than 9.8% under mesh topology circumstances when duty-cycle is stable; it also shows that the new protocol prolonged lifetime by 17.3%, reduced re-broadcast ratio by 8.6% when network scale is stable. The new protocol is suitable for data broadcasting and stands value in engineering applications.