Real-time Communication Technology Research In Wireless Sensor Network

With the development of wireless communication and sensing technologies, industrial wireless sensor networks(WSN) havebecome a hot research area. In the industrialproduction process,rapid respond to the change ofequipments and plantsis needed, which leads to a more strict demandon end-to-end delaythan traditional WSNs. At the same time, high reliable link is also needed due to severe interference and obstacles existing in the industrial environment.WirelessHART is an open standard specially designed for the harsh industrial communication environment which improve the reliability greatly. However thereal-time communication is still a open problem. Therefore, how to schedule date flows in wirelessHART based WSN to meet the real time requirement becomes a urgent need.In wireless HART based WSN there are multi-paths between each pairs of nodes,Since the conflicts may exist between these paths. The confliction of the paths are estimated, then a set of paths are selected to minimize the confliction of the whole network whileguaranteing that each flow has at least one path to forward. It reduces the probability of confliction between different data flows. Based on thewell-known EDF and FCFS strategy, a dynamic priority scheduling strategy RRA-EDFcombined the residual length of path and EDF is presented.By estimating the residual time that the packages reach the destination, a more fair priority assignment is achieved.Our experiment results show that the pre-path-selection can reduce the probability of confliction between different flows significantly and can improve the performance whatever the schedulingstrategies are used. Compared with EDF and FCFS, RRA-EDF can provide a more fair scheduling for periodical data flows and result in lower average delay and lower missing rate.