Research On Mobility Management Of 5G-NR Based On Intelligent Beam-switching Mechanism

The millimeter-wave frequency is exploited for mobile communication because it can provide large bandwidth to achieve the unprecedented data rates for 5G mobile communications systems.The adoption of massive Multiple-Input Multiple-Output technology can generate multiple beams in base station and the terminal.The introduction of multi-beam between base station and terminal has to be precisely and quickly aligned.The beam alignment will not only increase the delay for link establishment but also cause a significant impact on high-frequency mobility management processes such as initial access,beam switching,and tracking.In this thesis,the high frequency mobile beam management optimization algorithm under 5G typical scenarios is studied in order to greatly improve the system performance.Based on the current research on the development trend of mm Wave technology and 5G communication,the main contents of this thesis are as follows:(1)Technical background is deeply analyzed,including the state-of-art of the combination of mm Wave and the basic principle of beam mobility management.In order to reduce the switching rate of base stations,ping-pang switching rate and system switching delay,the study in this thesis is based on the parameter configuration with respect to beam mobility management in 3GPP NR protocol.Different impact factors and performance indicators that need to be balanced in 5G network design have been considered in this study.(2)The thesis considers the non-independent and independent 5G network modes according to whether the network supports LTE coverage.For the NSA network mode,a core network is configured with two base stations,and the mobile terminal can overcome the interruption of a link by switching data paths.In contrast,the SA network mode does not include LTE coverage.Compared with the former,the LTE connection can be used to report the best direction to g NB,and the UE does not need to wait for g NB to scan all the additional beams before performing the initial access operation,thus it can reduce the IA delay for UE.Meanwhile,the thesis considers the downlink configuration conforming to 3GPP releases,it can reduce the energy consumption of UE.The DL-NSA network mode is considered to provide an effective guarantee for the performance improvement of highfrequency mobility management.(3)Based on the research of traditional beam switching algorithm,a more efficient and reasonable beam switching algorithm in high-frequency moving scene is proposed in this thesis.First,according to the characteristics of different typical 5G scenarios,specific network scenario model,user mobile model and configuration scenario parameters are constructed.Based on the performance indexes of switching delay and signaling overhead,this thesis proposes an optimization algorithm for high-frequency mobile beam management based on the trigger mechanism of beam switching and switching criteria aiming at subdivision scenarios and network deployment in different millimeter wave scenarios.Combining the characteristics of different typical scenarios and terminal mobile models,the performance of different beam management optimization algorithms and baseline schemes is simulated and compared.Simulation results show that the proposed algorithm can reduce cell switching time delay and the unnecessary cell switching times can be also efficiently avoided.In addition,significant reduction of pingpang switching rate can be observed in the simulation result.The proposed highfrequency beam mobility management algorithms improve the performance in terms of system switching delay and signaling overhead compared with the traditional beam switching algorithm.The numerical result shows that the performance of high-frequency beam mobility management system can be improved by ?30%,under the premise of ensuring users' communication requirements.