| With the development of society and the progress of science and technology,especially the widely applications of the mobile communication network.The mobile communication requirements are increasing,such as network coverage,quality of services,large capacity of data transmissions.In order to improve quality of network services,the mobile communication network is innovating and improving constantly.To deal with the great challenges and requirements of various mobile communication network services,new technologies are presented and optimized in the 5G system.The separation of control plane and user plane is one of the key technologies in the 5G system.Introducing the C/U separation architecture into the 5G cellular heterogeneous networks,it can eliminate the interference of the same frequency and enhance the mobility of the users.In this case,however,the failure of macro base station will cause significant impacts on the system performance.Under the premise of reasonable system load and transmitting power,for the purpose of users' normal transmission in the control plane and optimization of the signaling load in the core network,the system need to reselect the neighbor macro base station or introduce a new base station.In addition,introducing the massive MIMO technology and deploying hundreds of antennas in the macro base station can greatly improve the quality of services in the system.Based on the 5G system,C/U separation and massive MIMO technologies,this paper analyzes the failure problem of macro base station in the cellular heterogeneous networks.The analyzing of users' mobile characteristics and load balancing in the system.We propose the effective neighbor macro base stations selecting scheme to optimize the signaling loads of the core network.Though the handover process,service analysis,transmitting power control and load balancing index constraints to reduce handover signaling processed in the core network and balance the network loads,and then increase the overall performance of the system.First,in the 5G cellular heterogeneous network systems based on C/U separation,a scheme of optimally selecting neighbor macro base stations is proposed,where the control plane of users interrupted under the coverage of the failure macro base station will be transferred to the selected neighbor macro base stations for the communication recovery.To give the optimal selection,the average handover rates between these small cells are analyzed based on the user motilities as well as the extended coverage of the neighbor macro base stations under the constraint of transmitting power.According to these analyses,the maximization of handovers processed by macro base stations is formulated under the constraint of load balance index,which is solved by slacking the variables and the convex optimization methods.The simulation results demonstrate that compared with the existing scheme,the proposed scheme can effectively reduce the signaling load of the core network.Secondly,based on the selective optimization of neighbor macro base station,the massive MIMO technology for macro base station is introduced.The macro base station selections scheme based on signal interference noise ratio(SINR)optimization is proposed.Based on the analysis of pilot transmission,the system measures the pilot pollution by the SINR parameter.Extending the coverage radius of the neighbor macro base stations,considering the relationship between the pilot pollution and the SINR performance in the system,we compare the difference of coverage radius and the location area of the same pilot users in the proposed scheme 1 and the proposed scheme 2.Then analyze the influences on the SINR performance of them,and obtain the macro base station selections scheme based on SINR optimization.The simulation results demonstrate that the proposed scheme 2 can effectively improve the SINR performance,increase the total processing handover ratio,reduce the signaling load of the core network and improve the system performance better. |
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