Research Of Beam Alignment And Tracking Based On UE's Mobility

Millimeter wave(mmWave)and massive MIMO systems are two key technologies for 5 G NR.On the one hand,the abundant spectrum resources in the mmWave band can greatly improve the data transmission rate.On the other,in order to compensate for the high path loss of mmWave,it is necessary to utilize the beamforming technology to achieve directional communication.In this case,the beam alignment is needed,that is,to find the best beam direction.The frequent beam direction switch brought by the rapid movement of the UE is a challenge to existing beam alignment algorithms.Moreover,because mmWave has a limited coverage and is prone to blockages,the researches in enhancing coverage of mmWave and countering blockage are of great significance.Firstly,we propose a beam alignment and tracking algorithm based on UE's location information to achieve fast beam tracking in high-speed scenarios.The algorithm combines two methods of the multiple beam search and location prediction.In most cases,the communication with high-speed UE is achieved through the line-of-sight(LOS)component.Under this premise,the optimal beam direction needs to be aligned with the LOS component.Therefore,by predicting the next location of the UE based on information of UE' s mobility,the range of the candidate beams can be reduced,thereby reducing the time complexity of beam tracking.The extended Kalman filter is used to predict the location of the UE at the base station(BS)side.Considering the possible errors in the predicted locations,we detect the accuracy of the location's predictions by comparing the Reference Signal Receive Power(RSRP)with a threshold.When the RSRP is higher than the threshold,the beam is aligned with the UE's predicted location.When the RSRP is lower than the threshold,multiple-levels search is used to conduct an initial beam alignment.Simulation results show that our proposed algorithm can ensure a small performance loss compared with exhaustive search,and substantially reduce the search complexity of beam tracking.Secondly,in this paper,a distributed antenna array deployment method is designed to enhance mmWave's coverage and combat blockages.Additionally,the UE is also equipped with multiple radio frequency chains to further improve spectrum efficiency.In order to maximize the sum rate,it is necessary to solve the beam matching problem between the UEs and the distributed antenna arrays.We solve this problem through maximum bipartite matching theory and stable matching theory,respectively.As a result,we design two algorithms,extended KM algorithm and extended GS algorithm.Simulation results show that the distributed deployment method can effectively resist blockages.It also verifies the advantages of our proposed beam matching algorithms.