Study Of Beam Management Techniques In 5G NR

The millimeter-wave Massive Multiple Input and Multiple Output(Massive MIMO)technology in 5G NR has become one of the key technologies to enhance system performance.However,millimeter-wave transmission has high attenuation,the propagation process is susceptible to environmental effects,and the beam width is narrow so that a single beam cannot provide stable and high-quality services to users in motion for a long time.Therefore,a more reasonable beam management process needs to be designed to ensure that the transmitting and receiving beam pairs can be replaced in time when the quality of the communication link deteriorates.In this paper,we study the beam management problem in NR system,especially the beam switching strategy in the user’s motion state is discussed in depth.The main research includes the following three aspects.Firstly,this thesis introduces the beam management framework in the existing protocol and introduces the beam switching strategy in SU-MIMO and MU-MIMO in detail.Based on the existing link-level simulation platform,the performance of this thesis is verified under the user’s moving scenario.The bit error rate and signaling overhead of different beam switching strategies are compared through the simulations.Secondly,in the single-cell scenario,a joint beam-domain and powerdomain optimization scheme is designed for the existing beam-switching strategy in which multiple users compete for the optimal beam to maximize the sum of the rate in the user motion scenario.For beam domain optimization,a greedy idea-based beam assignment algorithm is proposed,which can satisfy the user’s choice for the optimal beam as much as possible;meanwhile,in the power domain,a closed-form solution for the user’s power assignment factor is derived using convex optimization theory.Simulation results show that compared with the baseline scheme,the sum rate of cells is improved by 30%using the proposed joint beam and power domain optimization scheme.Thirdly,in the multi-cell scenario,a joint multi-cell collaborative beam domain and power domain optimization scheme is proposed for the poor performance of cell-edge users in the user motion scenario to maximize the average rate of cell-edge users.In the beam domain,edge users are judged by geographic location,suitable auxiliary cells are selected for edge users,and then neighboring cell-edge users and central users of this cell select beams by a collaborative beam allocation algorithm;in the power domain,a two-layer power allocation scheme is designed.Firstly,based on the game theory idea,the power allocation factor for each set is calculated for the edge user set and the center user set;then,the power allocation factor is calculated for each user in the two sets by the proportional fairness idea.The simulation results show that the average rate of edge users is improved by 23%compared with the baseline scheme.