Research On Gateway Placement And Routing In Satellite-terrestrial Integrated Networks

The Satellite-Terrestrial Integrated Networks(STIN)have the advantages of wide coverage,large capacity,and high reliability.STIN can provide high-speed and efficient wireless access services for the growing new business,which is an important way to realize communication globalization.However,the problems of heterogeneity,multi-path,complex network structure,and time-varying topology of STIN pose challenges to the effective connection and integration of the network.As a significant node connecting heterogeneous networks,the placement of gateway and rout selection will affect the network reliability.Therefore,this thesis studies gateway placement and routing in STIN,and the specific content covers the following two aspects:1.In the research of gateway placement in STIN,aiming at the problem that timevarying links and failed nodes will affect the connectivity of heterogeneous networks,the reliable placement of gateway under delay constraint is studied.Firstly,a network model is constructed with a Geostationary Earth Orbit(GEO)satellite,gateways,and switches.Then,the network reliability is defined by considering the probability of traffic distribution and network connectivity,and the gateway placement problem is formulated to maximize the network reliability under the constraint of propagation latency,which is obtained by path selection via Dijkstra algorithm.Following that,a Discrete Particle Swarm Optimizationbased Intelligent Gateway Placement(DPSO-IGP)algorithm is proposed to solve the gateway placement problem.In DPSO-IGP,the improved K-means method is given to reduce the search scope,and the gateway locations with maximum reliability are determined in virtue of DPSO.Simulation results demonstrate that the proposed DPSOIGP can reduce the latency and improve the network reliability.2.In the research of routing in STIN,aiming at the frequent changes of satellite network topology and the problem of multi-path,the multi-path selection in double-layer satellite network is studied.Firstly,a network model is built by GEO satellites,Low Earth Orbit(LEO)satellites,and terrestrial nodes.On this basis,the terrestrial nodes select the LEO satellite with the shortest distance to access the network,and then the objective function of link cost optimization is established.Following that,a Multi-Path Routing with Guaranteed Reliability(MPR-GR)algorithm is proposed.In MPR-GR,the best next hop satellite node is selected by latency,the number of hops and remaining bandwidth,the node disjoint scheme is used to search for multi-paths with guaranteed reliability.Simulation results prove that MPR-GR algorithm can raise network throughput,reduce latency and packet loss rate.