Study On Three-dimensional Scene Channel Modeling And 3D MIMO Beamforming Schemes

As the transmission medium of wireless communications,the radio channel directly affects the transmission quality of the wireless communication system.It is an important way to establish a radio channel model for analyzing the radio channel characteristics and performance of wireless communication systems.The three-dimensional ray tracing technology is a deterministic channel modeling method.The tracing technology is widely used in the propagation prediction because it can establish accurate channel modelOn the other hand,data traffic increases rapidly with the development of mobile Internet.The reality demand promotes people to improve the existing mobile communication network and system capacity.Compared with the traditional MIMO technology,3D MIMO and 3D beamforming technology can distinguish the users from the horizontal and vertical dimensions,reduce the inter-user interference and inter-cell interference,and then improve the system throughput and spectral efficiency.3D MIMO is a promising future development direction of the MIMO technology,and it is also a hot topic in the currently 3GPP standardization work.Based on the above background,this paper focuses on the theory of three-dimensional ray tracing technology and 3D MIMO beamforming technology,and has completed the following work:The first,designing and implementing a ray tracing program can be used for general scene and this program will use a three dimensions ray tracing algorithm based on triangulation.In this algorithm,the three-dimensional scene is first divided into several tetrahedrons,and then the program will calculate the trajectory of rays in these tetrahedrons,combining with the principles of geometric optics,Geometric Theory of Diffraction and Uniform Theory of Diffraction.Finally,the distribution of field strength in the scene will be calculated by the program.The basic principle,entire design and detailed design of the ray tracing program will be introduced in this paper,and the simulation results of this method will be compared with the simulation results of ray tracing algorithms which based on SVP.It shows that the accuracy of two simulation results is similar.The ray tracing algorithm based on triangulation can reduce the time consumption of intersection testing between the ray and the polyhedron surface,and it has improved the efficiency of the algorithm.The second,designing a low complexity 3D MIMO beamforming scheme based on 60GHz millimeter wave TDD system,and realizing the corresponding beamforming scheme simulation platform.The 3D beamforming scheme use a kind of Kronecker product based 3D codebook.The codeword matrix is intercepted or sampled in order to change its antenna pattern,and then we can use a three-level classification method and a horizontal and vertical combination classification method.During the beamforming training process,the system can search the different spatial resolution codebook progressively and find the most suitable beamforming vectors.This paper also uses the IEEE 802.11 ad channel model to evaluate the beamforming scheme in the LoS and NLoS scene.The simulation result shows that the beamforming scheme is more suitable for LoS scene compare to the NLoS scene.This 3D beamforming scheme can improve the codebook searching efficiency,and the user SINR has improved compare to the 2D beamforming scheme.It can further enhance the user SINR and optimize the system performance if the precoding is used in the interference suppression.