Message Distribution Technology For Space-based IoT Satellite Gateways

With the rapid update and iteration of information and communication technology,Internet of Things(Io T)has been sufficiently developed and popularized.Nowadays,it has changed the traditional way of life and work of human beings and enabled many industries to embark on the road of intelligence.To a certain extent,the development of the Io T depends on the level and capacity of the current communication infrastructure.However,it is difficult to deploy the ground network in some remote areas,vast deserts and distant sea.What's more,the coverage of base stations is small,so as there's usually no signal in these areas,which leads to the service ability of the Io T technology can not meet the demand of human beings.In order to solve the disadvantages of the terrestrial Internet of Things,which is greatly affected by the region and limited coverage,it has become a mainstream trend to utilize satellite communication to serve the Io T.Based on the advantages of three-dimensional full coverage of LEO satellite,this dissertation constructs a space-based Internet of Things architecture based on LEO satellite communication,which realizes the ubiquitous of the network and the extensive access of user terminals,and provides reliable communication services for the ground.Aiming at the problem of message transmission in highly dynamic satellite network,this dissertation designs the message distribution technology of satellite gateway.Considering the impact of the online status of ground devices on message transmission,two scenarios of active long connection and passive short connection are modeled respectively,and the corresponding technical design schemes are proposed.Finally,it builds a spacebased network simulation platform by using docker container virtualization technology.An example test is carried out to verify the reliability and latency performance advantages of the message distribution technology in the satellite gateway scenario of the space-based Internet of Things.The specific research contents and contributions of this dissertation are as follows:(1)Aiming at the problem that the terrestrial Internet of Things is greatly affected by the region and limited coverage,a architecture of space-based Io T based on LEO satellites communication is constructed to achieve the ubiquitous of the network and extensive access of user terminals to provide reliable communication services for the ground.(2)The key problem is solved that searches achievable route in the active long connection scenario of space-based satellite network.When the terminal device sends data to the LEO satellite gateway covering the area where it is located,the terminal device remains online,and the user can directly obtain the required data from the terminal device,which belongs to the scenario of active long connection.In this scenario,a steady-state processing method of the satellite dynamic network,namely the space-time connection graph model,is used to obtain the steady-state graph of the satellite network in different time slots.On the basis of the steady-state graph,the improved algorithm of Dijkstra is used to obtain the routing between users and remote Io T devices,so as to realize reliable transmission of data.(3)The key problem is solved that realizes distributed consistency in the passive short connection scenario of space-based satellite network.When the terminal device sends data to the space-based satellite gateway covering the area where it is located,the terminal device enters the silent state,and the user cannot directly obtain the required data from the terminal device,which belongs to the passive short connection scenario.In this scenario,a publish/-subscribe message distribution mechanism and Raft distributed consistency algorithm are introduced in this dissertation.Io T devices enter a silent state after publishing messages to satellite gateways,and satellite gateways use Raft distributed consistency algorithm to realize the replication and transmission of data among satellites.Users subscribe messages to Io T devices directly by connecting with the satellite gateway covering their area,so as to realize message transmission between ground users and devices in the scenario of short connection.