Research On Reliable And Efficient Beam Handover Technology For Satellite Internet

Space-air-ground integrated network(SAGIN)is an important development trend of 6G.Low orbit satellite(LEO)constellation has the characteristics of low delay,low link loss,low cost and wide area coverage,it has become an important idea for the construction of satellite network in the future.The Space-air-ground integrated network has been widely discussed in the industry and academia,and is even expected to be applied to large-scale constellations under construction.The construction of satellite Internet will effectively realize reliable,high-speed and seamless communication in forest,desert,ocean,oil fields,mines and other key economic working areas.At the same time,due to the surge of global users and the uneven distribution of time and space of user business,in order to improve the utilization rate of on-board resources,the beam-hopping system came into being.New ways of using time-frequency resources also bring new challenges to mobility management.In this paper,the inter-satellite handover problem in satellite Internet is solved through the research of multi-attribute joint handover decision algorithm,the research of beam-hopping satellite group user handover scheme and the construction of simulation platform.1.In the Internet communication system of LEO satellite,single factor including power,ephemeris,channel quality,elevation and other factors,will be considered as the decision basis for handover.If the single factor is used as the handover criterion,it will cause frequent handover and wrong handover,handover delay and dropped calls,high complexity or low accuracy.In order to solve the handover problem of LEO satellite with variable scene and multiple influencing factors,the second chapter of this paper discusses multiple influencing factors of handover.In the third chapter,a multi-attribute joint decision handover algorithm based on reconfigurable factor graph is proposed,which uses multi-factor joint decision to improve the dynamic adaptability of handover decision.2.In the fixed beam and gazing beam scene,the prediction error is large,and the precise and accurate handover time cannot be calculated.At the same time,the user model used in the traditional inter-satellite handover scheme is the uniform distribution model,which is simple,subjective and static,and cannot accurately describe the user distribution under different spatiotemporal conditions in the actual ground environment.The main problem of this strategy is to treat a beam as a whole,that is,all users adopt the same handover time.However,due to the uneven distribution of users,especially when the distribution of users is concentrated at the edge of the beam,it is easy to cause some users to handover prematurely or delay.In addition,most of the current studies on handover schemes in the beam-hopping scenario of LEO satellites only apply the handover schemes in the traditional fixed-beam scenario to the beam-hopping scenario,without making targeted changes and adaptations.Therefore,aiming at the handover model of low-orbit beam-hopping satellite communication system when users are not uniformly distributed,we analyze and describe the problem in Chapter 4 of this paper,and propose a group handover scheme based on survival drive and multi-user time sequence diagram to complete the handover control of the beam-hopping satellite communication system.3.In order to verify the multi-attribute joint decision handover algorithm and inter-satellite group handover scheme proposed in Chapters 3 and 4,this paper uses OPNET and STK to build a low orbit satellite Internet simulation platform.Firstly,the design of satellite constellation is completed based on the STK platform to simulate the real coverage of the satellite.Secondly,the interface between heterogeneous platforms is designed to complete the data transmission between the two platforms and the characterization of simulation results.In order to truly simulate the communication protocol process,based on and improved 5G ground protocol stack,satellite Internet protocol stack is built in OPNET to complete the handover process,and the designed beam-hopping satellite handover scheme is deployed and applied.Finally,the performance of the proposed multi-attribute joint decision handover algorithm and beam-hopping satellite group handover is verified.