Optimization Age Of Information For IEEE802.11ah IoTs

With the popularization of computers,the deployment of the Internet of Things(IoTs)is developing very rapidly.The success of the Internet of Things lies in enabling a large number of devices to communicate through machine-to-machine(M2M)communication.The Internet of Things is widely used in many fields,such as smart cities,transportation systems,industrial and agricultural automation,healthcare and power grids.The demand for timeliness of information is getting higher and higher,and real-time information is becoming increasingly important in the development of the Internet of Things.Age of Information(AoI)is used to measure the freshness of Information fragments,which has certain advantages in improving the timeliness of Information in the Internet of Things.Considering the importance of maintaining state information of physical processes in Internet of Things applications.Flush the target node as much as possible for effective monitoring.IEEE 802.11 ah is a low frequency and low consumption WLAN technology proposed for the application of the Internet of Things.The technology has the advantages of wide coverage,many nodes and high network speed.In the IoT system based on IEEE 802.11 ah protocol with real-time application,the equipment needs to sense the changes of the surrounding environment in real time and monitor the system state,so as to provide timely and effective information for efficient decision and control.In order to improve the timeliness of information in the Internet of Things,three schemes are proposed to improve the IEEE802.11 ah network:(1)In view of the complexity of 802.11 ah network topology and the low timeliness of information caused by the collision of nodes,a grouping algorithm based on network topology is proposed to group network nodes under different network topologies.The algorithm calculates the degree of all nodes according to the constructed connection matrix,then selects cluster head nodes according to the degree of nodes,finds neighbor nodes according to cluster head nodes,and finally divides cluster head nodes and their neighbor nodes into a group.Simulation on Python shows that the algorithm can be applied to different network topologies.At the same time,grouping also reduces the conflict in the network and improves the timeliness of information transmission.(2)As the backoff mechanism of 802.11 ah channel access mechanism adopts binary exponential backoff,the conflict and collision will be caused by small competitive window value under high load,and the backoff delay will be too long due to large competitive window value under low load.An adaptive competitive window backoff algorithm based on collision probability is proposed.The algorithm can set the competition window value according to the collision probability,which is flexible.The simulation results show that the adaptive competition window retreat mechanism based on collision,CW can reduce collision and collision under high load and channel retreat delay under low load.It reduces the age of network information,improves the timeliness of information,and improves the network throughput.(3)Aiming at the RAW channel access mechanism proposed by 802.11 ah,this paper analyzes the transmission mechanism based on DCF in RAW,and it is difficult to avoid the collision,delay and other problems in the transmission process,and puts forward a polling mechanism.This paper proposes a kind of polling mechanism.This mechanism reduces age of information by reducing the access delay of packets,ensures that the receiver can receive the latest information,and further optimizes the timeliness of network transmission information.Simulation results show that the proposed scheme has significant advantages in IEEE 802.11 ah WLAN with dense congestion,and can effectively reduce information age and improve network throughput.