Research And Design Of Control Plane For 5G UDN

Ultra Dense Network(UDN)is one of the key technologies to meet high-capacity and high-rate performance indicators of 5G wireless network in the future,but the implementation of UDN faces many difficulties and challenges.First,because 5G wireless network is complex,dense,and heterogeneous,UDN suffers serious interference.Second,for low-power micro-cells covering extremely small area and micro-cells deploying densely,users handover more frequently between cells.In the dual-connection scene of the macro-micro network,the macro base station frequently adds and changes small cells to the user terminal,which greatly increases the signaling load and brings serious signaling burden on the radio access network and the core network.The above problem also declines the quality of user service.Finally,in order to cope with multiple service scene of 5G network,the UDN network is complex to deploy and costs much.In order to solve the above problems,this thesis researches two aspects on UDN: handover management and network architecture.The main research points are as follows:1.Firstly,an unnecessary handover scene is proposed.When the user's service is not active and the base station performs inactive detection,the terminal has a handover requirement,which may become an unnecessary handover.Therefore,this thesis first predicts the probability of service data arrival during inactive detection according to history of user's service.Then determine the user's active status based on the probability of service data arrival.When the user is active,handover process deals with the handover requirement.Otherwise,the user terminal is set as INACTIVE state by state transition,and then residences in the appropriate through cell reselection.The simulation results show that,compared to the handover process,the state transition has a significant reduction in signaling load and handover frequency.But there will be a small increase in the interruption delay.2.To deal with the complex and high-cost network deployment for the UDNnetwork,5G radio access network architecture determines the network structure separated by logical functions of CU(Central Unit)and DU(Distributed Unit),which could be deployed flexibly and decrease network deployment cost,at the same time,to achieve better cell coordination.In this thesis,the main functions of F1 application protocol(F1AP)between CU and DU are studied.F1 AP interface message,thread of both CU and DU,F1 module,inter-layer message interface,and centralized message processing are designed and implemented.