Handover Performance Analysis And Optimization Of Ultra Dense Networks In 5G

The rapid development of 4th generation communication system has been massively commercialized,which brings convenience to social activities and promotes the economic development.Huge of multimedia services,online games,smart phones and the Internet of Things connections urge the explosive growth of mobile data traffic and the connections between massive devices.Therefore,the performance of 4G network cannot satisfy the application requirements of users such as data transmission rate and network capacity.Thus,the 5th generation communication system emerges.Ultra Dense Network(UDN)is considered as a promising technology to satisfy the needs of dramatic capacity growth in 5G network.Besides that,it can also improve the spectrum efficiency and thousandfold increase network capacity in hotspots by deploying lots of low-power and low-cost femto access points(FAPs)in a macro cell.However,high density of FAPs will lead frequent handovers and high Ping-Pong handover rate,so it is difficult to guarantee the service continuity.In this dissertation,we investigate the mobility management of UDN scenario of 5G,which includes establishing an accurate theoretical performance analysis model for handover and optimizing the handover parameters in different scenarios.In this work,considering the existing inaccurate handover model and its corresponding unspecific handover performance index,we establish a theoretical model by introducing a power compensation factor to analyze the handover performances between FAP and macro BSs.Besides that.the correlation of shadow fading and the handover trigger process are accurately modeled by multivariate Gaussian integral.Then,the closed form expressions of handover probability and handover failure probability are derived according to the 3 GPP TS 36.839.The simulation results verify the accuracy of the proposed analysis model.Then,the methodology of UDN handover performance simulation platform is investigated.First,according to traffic density and radio propagation environment,the application scenarios of UDN are divided into the hotspot coverage scenario,residential areas and core office areas,and the Internet of Things scenario.After that,the handover signaling procedure and the handover performance such as handover failure and Ping-Pong handover are analyzed.Finally,the radio environment of UDN that consist of millimeter-wave path-loss model,correlated shadow fading map,and small-scale fading is simulated.Furthermore,the bilinear interpolation algorithm is applied in the shadow fading map to enhance the accuracy of the spatial correlation of the shadow fading in UDN.Finally,we evaluate the handover performance and optimize the handover parameters of UDN.After that,we compare and analyze the handover performances of LTE and UDN of 5G.Specially,the handover performance and its corresponding parameters of UDN are analyzed under different shadow fading parameters and different BSs density.To conclude.in this dissertation,the handover performances of UDN in 5G are investigated.We establish an accurate theoretical analysis model of handover in UDN and derive the closed expression of handover probability and handover failure probability.Then the relationship among the handover performance,handover parameters and shadow fading parameters are analyzed and the handover parameters in different scenarios are optimized.This work lays foundation for solving the handover problem in UDN and further improving the handover performance.