The Researchment Of Precoding Technology In 3D MIMO System

With the appearance of Active Antenna System(AAS),3D-MIMO(Three Dimension Multiple-Input Multiple-Output)has become the key technology of 5G system,which not only realizes the control of beamforming in the horizontal direction,but also makes full use of the freedom of the vertical channel space.Since the number of available antenna ports limits the use of number of antennas,and the signal can only transmit single stream data in the horizontal and vertical direction,it is necessary to redesign the 3D precoding multi-stream transmission scheme to adapt to 3D antenna array.Meanwhile,due to the increasing of interference and co-competition channel resources between service users,multi-user precoding technology also needs further study.Focused on the issue that how to realize multi-stream transmission in the horizontal and vertical direction of 3D-MIMO system,firstly,the different design methods of precoding in 3D-MIMO system are studied.Then,based on the channel state information reference signal(CSI-RS),independent and beamforming precoding scheme are studied in 3D-MIMO system.Next,combination of the Kronecker product 3D-MIMO precoding and CSI-RS port designs,a multi-stream transmission scheme in horizontal and vertical dimensions is proposed.Finally,the simulation gives the influence of different streams in the horizontal and the vertical direction on the system capacity.Aiming at the design problem of multi-user precoding in 3D-MIMO system,firstly,the multi-user limited feedback system model and multi-user precoding schemes are introduced.Secondly,the average throughput and fairness of multi-user scheduling are studied.Then,the separate and joint 3D codebooks are designed,and based on the orthogonality of precoding vector in codebook,a multi-user 3D precoding scheme is proposed.In view of the unfairness of the scheme,the idea of round-robin scheduling and proportional fair scheduling are introduced.Finally,through simulation,the influence of horizontal and vertical dimension feedback bits on the system capacity,and the system throughput and fairness of the three scheduling schemes are compared.