Design And Implementation Of Space-based Internet Of Things Protocol Based On NS3

With the development of the Internet of Things,it has brought great convenience to human life.The Internet of Things based on satellite constellation is a new direction of communication development,providing a complementary solution for the ground IoT system,which can be provided in the ocean and remote areas.Internet of Things services have the advantages of wide coverage,low construction cost and strong resistance to damage.In the space-based IoT scenario,the number of terminals is huge,and the data has a low duty cycle.If a fixed channel allocation strategy is adopted,unnecessary signaling interaction will be brought about,the channel utilization rate will be greatly reduced,and the time is increased.Delay.For the characteristics of space-based IoT,it is necessary to design appropriate communication protocols,including application layer,network layer,data link layer,physical layer and so on.Based on the characteristics of space-based Internet of Things,this paper analyzes the existing terrestrial wide area network and satellite communication technology,and proposes an IoT access layer protocol stack design suitable for low-orbit satellite constellation.Firstly,the enhanced spread spectrum ALOHA technology is adopted in the protocol design.The terminal asynchronous access does not need to allocate a fixed channel,and the anti-interference ability is improved,and the requirement of low power consumption of the terminal is reduced.In the protocol design,the channel mapping scheme of the air interface protocol stack is given,and the terminal random access policy is designed.Under the premise of ensuring security,the number of signaling interactions is reduced.In order to reduce the delay and reduce the dependence on the terrestrial network,the scheme of authentication information on-board storage and on-board authentication is proposed.On the other hand,in order to avoid the terminal multiple authentication,considering the mobility of the satellite,the UE context is stored in the gateway,and the scheme of only one authentication is reported multiple times.Finally,based on the open source NS3 discrete event simulation platform,the software implementation of the protocol is designed and developed,including the physical abstraction layer,data link layer,RRC layer and other parts to achieve basic data transmission and reception functions,and basic functions such as scheduling,paging and load control are developed.The simulation program can be used to verify the protocol design scheme and to improve the related protocol algorithm.