Research On Raw Mechanism Based On IEEE 802.11ah MAC Layer

With the popularization of Internet of Things(Io T)in the fields of electronic health,intelligent monitoring,intelligent transportation,home and industrial automation systems.the existing low-power Io T communication has been unable to meet the needs of devices for large-scale access and long-distance transmission.The Wi-Fi Alliance proposed IEEE 802.11 ah standard to meet the access requirements of such large-scale networks.In order to reduce the conflict probability in the process of wireless device access in high-density scenarios and reduce the competitive cost of devices,Restricted Access Window(RAW)mechanism was introduced in this protocol.Since the 802.11 ah protocol does not specify any RAW grouping standards,this grouping can seriously affect RAW performance.Therefore,this thesis mainly studies the influence of the way of station division on this mechanism,and the main work is as follows:Firstly,this thesis evaluates the performance impact of parameter setting on RAW mechanism,including RAW grouping number and packet transmission rate,and the mechanism was implemented based on ns-3 network simulator.The simulation results show that when the number of stations is the same and the transmission rate is different,the grouping parameters can significantly affect the throughput and average delay of the network.When the transmission rate is the same and the number of stations is different,compared with the RAW mechanism when randomly selecting the number of RAW grouping,the RAW mechanism when rationally seting the number of RAW grouping can significantly improve the network performance of the system,especially under high load.Considering the traffic demand of Internet of things devices,this thesis proposes a RAW time slot allocation algorithm based on traffic demand,which is regrouped according to the traffic type of sensors and reasonably distributes time slot resources according to the traffic demand.The simulation results show that,compared with the existing RAW mechanism,the time slot allocation algorithm considering the node traffic requirements can significantly improve the network throughput and reduce the average delay and energy loss,especially in the case of large-scale node transmission at a high rate.The research results of this thesis have important reference value for improving the access efficiency of MAC layer in IEEE 802.11ah system.