The Research Of Priority-Based MAC Protocol For WSN

WSN is a multi-hop self-organized network which is composed of a large number low-cost and small sensor nodes. The sensor nodes communicate in wireless way, and transmit the information to observer what sensor nodes sense, collect and process. In WSN, MAC protocol manages and distributes the shared wireless communication resource, and influences the performance of WSN in directly. WSN is application network, and need support to deal with incident in specific application in order to reduce the delay of important data with incident information. Meanwhile, energy is the bottleneck of WSN, and it is crucial to achieve energy efficient transmission under the premise of important data are transported in higher priority.An improved S-MAC protocol is proposed based on data priority and energy priority. The way is adjust the backoff time according to priority in order to reduce the transmission delay and prolong the lifetime of network. The improved protocol is realized in NS2. This paper's main work is as follows:(1) This paper improved the IEEE 802.11 data frame to realize the portability of data-priority. The priority of data is identified according to a correlative strategy at the source node in WSN. Both data and its priority are encapsulated into a frame and transmitted between nodes in network. So it is realize the rapid transfer whether in source nodes or in the middle nodes.(2) This paper improved S-MAC protocol on the basis of data priority and energy priority, in order to reduce the transmission delay of higher-priority data and prolong the lifetime of network. When forwarding a data frame, the node adjusts the contention window dynamically according to data priority and energy priority to make sure that the higher-priority data frame are forwarded in higher priority and collisions are reduced.(3) In NS2, this paper realized the improved protocol and test its performance. The experiments showed that the delay of higher-priority data is lower obviously, and the dead nodes are reduced to almost 30% in network, and lifetime of WSN is also prolonged. In this paper, an improved S-MAC protocol is proposed based on data priority and energy priority. The improved protocol not only achieved the efficient transmission for higher-priority data, but also prolonged the lifetime of WSN.