Research On Dynamic Handover Stragegy In Satellite-Terrestrial Integrated Networks

With the continuous development of the network,a single satellite network or terrestrial network can no longer meet the increasing traffic demand of users for the increasing change of various emerging services and data traffic and the increasing demand for communication quality and services of mobile terminals.Satellite-terrestrial integrated network(STIN)formed by the integration of satellite networks and terrestrial networks can overcome the shortcomings of each single operation,and provide global coverage and information support for various types of services.However,due to the differences between different network nodes result in problems such as dynamic changes in network connections and frequent link switching.To solve these problems,this thesis focuses on the dynamic handover strategy in STIN.The main contents are summarized as follows.Firstly,aiming to the problem of frequent handover between low-Earth orbit satellites and mobile terminals and the degradation of service quality due to the dynamic mobility of the nodes in the STIN.A handover Strategy based on Multi-Attribute Dynamic Graph(MADG)is proposed.First,a STIN model composed of LEO satellites and mobile terminals with different mobility characteristics is constructed,and the link connectivity is analyzed to obtain the information of available path.Then,comprehensively considering the elevation angle,coverage time,and free channel state,MADG is introduced to represent all possible switching paths,thereby modeling the switching problem as finding the best path from the available paths.At the same time,the problem of multi-service data transmission of STIN is analyzed,and assign weights for different service requirements by multiple attribute decision making(MADM).Finally,the optimal switching path is selected according to the edge weights by the Floyd algorithm.Simulation results show that the proposed handover strategy can effectively reduce the handover delay and the handover blocking rate.Secondly,aiming to the problem of frequent overloading of STIN links and changes in service volume that cause excessive load,a dynamic matching handover strategy based on load balancing is proposed.First,a STIN network model is constructed with the terrestrial network,satellite network and user terminal.After that,a Markov chain is introduced to describe the dynamic state transition of STIN.Then,the load factor is defined by the ratio of the amount of traffic that can be accessed through the network to the total volume of traffic and an optimized model for the load is established.At the same time,focusing on users and networks,evaluation models are designed to evaluate the preferences of both parties for each other and establish corresponding sorting queues.Finally,based on the information of sorting queue,the optimal switching network is obtained to matching users and networks by a matching model.Simulation results show that aforementioned strategy can better load network balance,reduce network switching delay and user blocking rate.