Research On Multi-User Low Delay Minimal Access Technology For Time Sensitive Service Of Satellite Internet

As an important part of the 6G communication network in the future,the low-orbit satellite communication network has attracted much attention in all walks of life at home and abroad.It has the advantage of breaking through the geographical and topographical restrictions to achieve seamless coverage of global communication.Low-orbit satellites are characterized by fast moving speed,wide coverage area,long communication distance,large signal attenuation,large number of serviceable users and limited available resources.As a result,the existing access mode in the ground scene is no longer applicable to the low-orbit satellite network,and it is difficult to meet the transformation of the communication architecture from user-base station to user-satellitegateway station.In the low-orbit satellite network scenario,non-uniformly distributed users and time-sensitive services have high requirements on service quality.In order to provide reliable access services for users,the low-orbit satellite network needs to provide random access capability with non-uniformly distributed users.In this thesis,three key problems of user and service distribution,minimalist random access and user collision processing in the low-orbit satellite scenario are discussed.1.At present,the construction and research of satellite communication network are in the immature stage,which cannot provide users with efficient,reliable and fast communication.The analysis of user and service distribution in satellite scenarios is an important means to solve the problem of cell selection random access and handover performance optimization in satellite communication.In this thesis,a spatio-temporal service distribution model based on global thermal map is proposed to provide reliable prior information for satellite Internet user access.2.The low-orbit satellite scenario is characterized by uneven user distribution,few available resources and large satellite-earth distance difference.In the process of access,users cannot accurately confirm the arrival time of access feedback messages,which affects the reliability and real-time performance of user access and improves resource consumption.In this thesis,a two-step random access optimal response time determination method based on A3C algorithm is proposed.The method combines user distribution characteristics and satellite movement information to predict user propagation,processing delay and user delay difference in the process of access,and determines the optimal time window threshold.Simulation verifies that the proposed algorithm can meet user access requirements and obtain accurate feedback time window to reduce user resource consumption.3.In the low-orbit satellite scenario,burst communication users and high transmission delay are important factors affecting access performance.If different users select the same access resource for random access,access collision occurs.As a result,users need more time to complete access.Based on the research in Chapter 2 and Chapter 3,this thesis proposes a collision processing method based on spatial-temporal distribution constraints to reduce the probability of collision and ensure the user’s access performance after the collision.Finally,the collision processing method is verified by simulation.4.This thesis builds a system-level simulation platform based on STK and OPNET,and designs the simulation platform architecture and random access process.Based on this platform,the performance of the proposed method for determining the optimal response time of two-step random access for low-orbit satellites based on A3C algorithm and the access collision processing algorithm based on spatio-temporal distribution constraints are verified.