Priority-based Slotted CSMA/CA Algorithm Research And Implementation For Wireless Sensor Networks In Real-time Environment

As the fast development of Internet of Things,the prospects for Wireless Sensor Network(WSN)is very wide,the requirement of people for the performance of WSN is increasingly strict.In some special application scenarios,it is required to ensure not only high network reliability,but also low latency.The Slotted Carrier Sense Multiple Access/Collision Avoidance(CSMA/CA)plays a important role in WSN and has decisive influence on the performance of network.However,the standard CSMA/CA algorithm does not meet the requirements in some special scenes.Based on the standard CSMA/CA in IEEE802.15.4,this paper proposes a priority-based and adaptive slotted CSMA/CA in real time environment.Accroding to the different requirement for network performance,Devices are differed into different priority and the different value of BE and CW.In this paper,the topology of the network is star,coordinator collects the data periodically,calculates the channel busy ratio to evaluate the traffic load and transmits it with beacon payload.Devices dynamically adjust the back off period according to the traffic load of current network and the priority.Moreover,in the IEEE802.15.4 standard CSMA/CA,the transmission of Acknowledge may lead to the overage latency.This paper proposes the enhanced CSMA/CA based on more times CCA with the channel idle state flag to represent the results of CCA,avoiding unnecessary delay.We verify the proposed algorithm by the NS2 simulation tools.In the star topology network,the device nodes periodically generate data and use direct transmission mode to send it to the coordinator.In this paper,the effective transmission ratio is defined to characterize the reliability of the network and the end-to-end latency is recorded.In order to verify the feasibility of the proposed algorithm,the proposed algorithm,APB-CSMA/CA and the standard CSMA/CA algorithm are simulated and compared,the results demonstrate the proposed algorithm has better performance in terms of reliability and latency.In order to verify the feasibility of the proposed algorithm on the actual platform,this paper implements and verify the proposed algorithm on the actual platform based on IEEE802.15.4 standard software stack.Finally,we analyze and compare the proposed algorithm,the standard CSMA/CA in terms of reliability and latency on the actual platform.The actual verification results and simulation results are basically consistent,the network performance of the proposed algorithm is superior to the standard CMSA/CA.