Research On Beam Tracking Technology In Millimeter Wave Massive MIMO System

In order to meet the requirements of data transmission rate and energy efficiency,the antenna array size and communication frequency band and bandwidth in the field of mobile communication are constantly expanding.When the extremely large-scale antenna array(ELAA)is combined with the millimeter-wave massive multiple input multiple output system(MIMO),the wideband multi-carrier communication will be affected by frequency,bandwidth,and antenna scale and arises the beam split effect.The beam split effect reduces the directivity and beam gain of the communication beam,and also makes it difficult to adapt to the traditional beam training and beam tracking algorithms.Therefore,this thesis studies the beam training and beam tracking technology under the beam split effect.1)Beam training algorithms transmit training beams sequentially within the specified interval by searching one by one.When the number of antennas is large,the beams will become extremely thin,and indicators such as state usage efficiency and information representation efficiency will be greatly affected,and due to timeliness issues,the search success rate will also drop.This thesis takes advantage of the fact that the natural beam split effect in the system will make the beam coverage wider,and uses it for beam training.A beam rotation codebook based on the beam split effect is designed and implemented,so that the split beams are sequentially rotated,cover the target search interval,and complete a hierarchical training scheme with this codebook.In this scheme,it is necessary to consider and overcome the problem of inconsistency in the degree of splitting when the beam points to different directions,and select the reference beam accordingly,then calculate the entire rotating codebook with the reference beam as the core,finally apply it to the hierarchical training scheme.The simulation results show that when the number of antenna elements are more than 16 and 256 respectively,the state utilization rate and information expression efficiency of this scheme far exceed the traditional algorithm,and the more the number of antennas,the greater the advantage.2)In the traditional narrow-band millimeter-wave communication system,although there is no beam split effect,the beam width is still extremely thin.When performing beam tracking algorithm,it is necessary to switch beams flexibly to keep up with the moving speed of the target,otherwise there will be extreme tracking error and huge tracking overhead still exists.This part still adopts the idea that beam splitting can expand coverage,uses a new delay-phase precoding structure to generate frequency-dependent beams,and increases the variable of the frequency dimension during beamforming,which makes the generated sub-beams point to different directions according to different frequencies to achieve the purpose of artificial split,which is called dispersed beam in this thesis.Next,we implements a beam tracking scheme using the dispersed beams with wider coverage,and designs a highly dynamic communication scenario between vehicles and base station.The simulation results show that the tracking error of this scheme is an order of magnitude lower than that of EKF-based beam tracking,and has lower overhead,the convergence of the effective achievable sum rate is closer to the theoretical upper limit.