Research On Terminal MAC Layer Protocol In Satellite Iot System

In recent years,the Internet of Things technology has developed rapidly,and its application scenarios cover many aspects of social life.However,in some IoT scenarios such as environmental monitoring,land mobile communication base stations are difficult to build in areas with small population density and vast areas,as well as in oceans,forests,and mountains.It is impossible to provide Internet of Things services to these areas.Satellite communication technology is also evolving,satellite link capacity has increased and low-orbit satellite constellation design research has yielded some results.Therefore,low-orbit satellites are used instead of terrestrial base stations to serve IoT terminals.It will be one of the trends in the future development of the Internet of Things.However,satellite communication and terrestrial mobile communication are different in link conditions and communication distance,and there are also differences in the types of services.Therefore,the terrestrial mobile cellular communication protocol can't adapt well to the communication scenario of the satellite IoT.It is particularly important to design a communication protocol that conforms to the satellite IoT scenario.Aloha method can be used for access in the satellite communication,but the network throughput of the Aloha is poor.Therefore,selecting an appropriate MAC layer access algorithm is an urgent problem to be solved.This paper introduces the satellite IoT communication system and its research status.It also summarizes and describes the design and function of the MAC layer and related protocol layers.At last,this paper studies the MAC layer access algorithm.Aiming at the problem that the network throughput decreases with the increase of load in the existing MAC layer access algorithm,this paper proposes a distributed competitive connection based on the probability of user transmission according to the characteristics of the satellite IoT system.The method obtains the current network load condition according to the broadcast information of the access star,and then uses a genetic algorithm to calculate the transmission probability of each user under the current load.Each user independently transmits data according to the calculated transmission probability,thereby effectively improve performance such as network throughput and packet loss ratio.Secondly,this paper designs a specific protocol module for the MAC layer protocol of terminal and builds a software platform to verify the possibility of the protocol.The software architecture,random access module,channel mapping module and channel complex are designed and built in the software platform.The simulation verification of the paper shows that the distributed access scheme based on the terminal's transmission probability can effectively improve the network throughput and reduce the packet loss rate of the system.The MAC layer protocol software platform of terminal can also verify the feasibility of the protocol.