Research On Beamforming Technology Based On Lens Array In Millimeter Wave Massive MIMO System

Driven by various new service requirements,mobile communication networks urgently need to evolve to a new generation.The integration of millimeter-wave communication,Massive Multiple Input Multiple Output(Massive MIMO),beamforming,and lens antenna arrays has become a research hotspot in the field of wireless communication.On the basis of traditional MIMO,Massive MIMO expands the scale of the antenna array,which leads to extremely high hardware complexity and high energy consumption of the all-digital beamforming solution,which is impossible to implement in actual communication systems.Although analog beamforming reduces the energy consumption of the system,it lacks the digital domain processing process of the signal,resulting in low flexibility of the communication system,and only single data stream transmission can be realized,which affects the system performance.At present,the hybrid beamforming scheme is mainly used in the millimeter-wave Massive MIMO communication system,but most of the existing hybrid beamforming architectures use a large number of high-precision phase shifters to adjust the signal phase,and the hardware overhead and energy consumption of the system are still high.To further reduce the hardware cost and energy consumption of hybrid beamforming architectures,many technologies and designs have emerged.Recent related studies have proposed to introduce lens antenna arrays into millimeter-wave Massive MIMO communication systems.Using electromagnetic lenses,different phase shift characteristics can be generated at different positions,and electromagnetic signals incident at different angles of arrival in space can be concentrated on different antenna array elements.In the above,the adaptive switch structure is used in the beamforming architecture to replace the phase shifter for beam selection,which greatly reduces the hardware cost and energy consumption of the system.This paper focuses on the design of the beamforming scheme after the lens array is introduced into the millimeterwave Massive MIMO system.The work in this paper mainly has the following two innovations:First,a beamforming scheme of lens-antenna array based on adaptive switching structure in single-user system in narrow-band situation is proposed.Based on the phase shift characteristics of the lens array itself,the switch structure is used instead of the phase shifter to perform analog beamforming,thereby simplifying the beam selection structure and reducing energy consumption.The proposed adaptive switch structure has higher flexibility in antenna selection,adaptively allocates antenna subsets to each RF link according to channel conditions,and realizes digital beamforming by genetic algorithm.At the same time,combined with the block-diagonal zero-forcing algorithm,the proposed hybrid beamforming scheme is extended to multi-user communication systems.The second is to address the problems of power leakage,beam squint and multi-user interference in the application of lens antenna arrays in multi-user communication systems under broadband conditions.The beamforming scheme to optimize the system and rate is given.At the same time,the corresponding communication system model is given,the appropriate channel model and energy consumption model are established,the joint subcarrier beam selection(JS-BS)algorithm is designed,and the corresponding mathematical derivation is given.