Performance Analysis And Improvement Of Low Earth Orbit Satellite Iot Random Access Protocol

The past decade has seen a progress in the Internet of Things,areas such as transportation,healthcare,logistics,intelligent environment and online network have become important applications of the IoT.In the near future,the global IoT will be realized.However,the current terrestrial IoT has certain limitations.In sparsely populated or inaccessible areas,such as oceans,deserts,and so on,nodes or base stations in the IoT are hard to locate.However,satellite intranets can solve these problems.However,the Internet access technology for satellite connection also faces the challenge of how to solve the problem of conflicts and interference between users when multiple low-cost user terminals are connected at the same time.Therefore,it is very necessary to design an effective access scheme for the satellite IoT.This article first introduces the necessity of studying the satellite IoT,introduces the development status of the satellite IoT,points out the current challenges and difficulties faced by the satellite IoT,and then introduces the development status of the access protocol used in the satellite IoT,as well as the satellite IoT.The system architecture and business characteristics of the IoT,and the performance of the current random access protocols which are typical is simulated and analyzed,and the shortcomings of the existing protocol are obtained.Then,this paper proposes a random access scheme based on spread spectrum technology to solve the problem that the throughput and packet loss rate of the existing random access protocol can decrease sharply under high load.The effects of the length and number of spread spectrum sequences on the performance of random access protocols are analyzed,and the results show that the number of spread spectrum sequences has a more significant effect on the performance of random access protocols.The simulation results of random access protocol performance based on single spread spectrum are obtained by using Gold codes of r=5,6 and 7 respectively.In order to increase the number of spread-spectrum codes,m sequence and Gold sequence are proposed to be used to form a composite code,and then simulates the protocol,and obtains the simulation results of the performance of random access protocol based on secondary spread-spectrum.The simulation results show that the throughput performance and packet loss rate of the protocol are improved by the composite code composed of M sequence and GOLD sequence.Finally,in order to save system resources,a random access scheme based on traffic model prediction is proposed.Firstly,by observing the existing network activity data,a day is divided into 24 periods,and models are established respectively as the simulation and reference for the data of satellite Internet of Things application scenarios.After that,CFtool was used to fit the existing data to get the fitting curve,and then the traffic data in each period of time were predicted.According to the predicted value,on the premise of meeting the system performance requirements,the appropriate access mode can be selected in advance,which not only reduces the switching jitter,but also reduces the overhead and saves the system resources.