Design And Implementation Of 3D Massive MIMO Transmission Scheme Based On Codebook Enhancement

Three Dimensional Massive Multiple Input Multiple Output(3D Massive MIMO)technology has greatly improved the performance of wireless communication systems by equipping a large number of antennas at the base station and adding the vertical angle dimension,which has become a key technology in 5G communication.In order to further increase the system capacity and reduce the complexity of the system,a precoding scheme with limited feedback based on the codebook for the FDD system is studied.The specific research work is as follows:Firstly,this paper proposes a two-dimensional hybrid precoding with limited feedback for 3-D massive MIMO.When the base station is equipped with a uniform planar array,assuming that the vertical angle spread is small,the multipath Saleh Valenzuela channel can be approximately decomposed into two channel matrices with low dimensions by Kronecker product.The feedback criterion can be designed in horizontal and vertical dimentions respectively.Simulation results show that our proposed algorithm can obtain acceptable spectrum efficiency compared to other algorithms with much lower complexity.Also,this advantage will become more evident as the antennas increase.Secondly,we consider the application of nested antenna arrays in wireless communication systems.The nested antenna array is a concept used in array signal processing,but we creatively introduce it into wireless communication systems.The multipath Saleh Valenzuela channel model is derivated for 3D Massive MIMO with a two-level nested linear array.Based on the transformation matrix,we propose a brand new precoding structure with limited feedback.A virtual uniform array can be generated by the channel of the nested array and the transformation matrix,which generates more virtual antenna elements than the physical antennas.Simulation results show that our proposed precoding algorithm can obtain higher spectrum efficiency in nested massive MIMO systems compared to uniform massive MIMO systems with the same number of physical numbers.Also,this advantage will become more evident as the physical antennas increase.