On The Media Access Of Wireless Sensor Network

Wireless sensor network is a typical wireless network without infrastructure, which is made by the convergence of wireless communications, sensors, embedded computation, and network technologies. It can be used for testing, sensing, collecting and processing information of monitored objects. It can be applied in many areas such as military affairs, commerce, medical care, and environmental monitoring, which has attracted much attention to both academia and industries.Media Access Control (MAC) protocol decides the way what wireless channel used, distributes limited communication resource between sensor nodes, it becomes a focus of studying Wireless Sensor Network. MAC protocol in WSN are mainly classified into three types: contention based MAC protocol; time division multiple access based MAC protocol, and mixed type MAC protocol.After studying of the famous adaptive S-MAC(sensor-MAC) protocol, this thesis mainly proposes the modified scheme on delay based on S-MAC/AL (Adaptive Listening) which is modified S-MAC, while maintaining low energy consumption . Although S-MAC/AL reduces the average delay by half, transmission delay is very long for periodic sleep. The thesis proposed low delay modify to support one data packet can jump three hops in a frame time, which can significantly reduce the overall latency in multi-hop transmissions. Additionally, the thesis proposes the improved route adaptive listening, which control nodes who needn't join adaptive listening to go to sleep, and reduce energy waste.Afterwards, the thesis implements the improved protocol based on NS-2 and designs simulation experiments. In this thesis, AWK program methods are used to accomplish statistical analysis of trace file data extraction and three main attributes (latency, throughput, and energy) of network. The simulation results show that, in contrast with S-MAC, the improved S-MAC protocol improves average packet latency, and the data throughput. It is especially applicable to the wireless sensor networks applications that require delay strictly.