Design Of Hybrid Precoding Scheme In Millimeter Wave Massive MIMO System

After several decades of rapid development of mobile services,its business coverage has gradually moved from simplification to diversification.However,the upgrading of mobile communication technology has also brought about some problems,such as the increasing number of devices in the network,the lack of spectrum resources,and the limited spectrum efficiency.Since Massive MIMO and millimeter wave technology play a very important role in the effective use of spectrum resources,they have received the focus of attention of researchers.This paper discusses the design of hybrid precoding schemes in millimeter wave Massive MIMO system,the main work are summarized as follows:(1)A single-user millimeter-wave Massive MIMO system with partial connected structure is studied,and a hybrid precoding scheme based on improved particle swarm optimization algorithm is proposed for this system.Firstly,the particles' position vector and velocity vector are initialized randomly,and the initial swarm optimal position vector is given by maximize the system spectral efficiency.Then,the position vector and velocity vector are updated,and two updated particles' individual-historical-best position vector are randomly selected to do weighted sum as the new individual-historical-best position vector,and then some of particles that maximize the system spectral efficiency are picked out.The weighted average value of the individual-historical-best position vector of these particles is taken as the new swarm optimal position vector and compared with the previous one.After many iterations to form the final swarm optimal position vector that is the desired best hybrid precoding vector and normalize it.Finally,the final analog precoding matrix and digital precoding matrix are designed according to the normalized hybrid precoding vector.(2)A multi-user millimeter-wave Massive MIMO system with full connected structure is studied,and to address the problems of high complexity,the receiver optimization process needs to be strengthened and each user can only transmit one data stream when jointly design the hybrid precoder and combiner in traditional multi-user millimeter wave Massive MIMO system,a new scheme for designing hybrid precoders and combiners separately is proposed.Firstly,the analog combiner is designed by singular value decomposition of the channel matrix,and the analog precoder is designed according to the equivalent channel gain.Secondly,the digital precoder is designed based on the equivalent analog channel generated by the analog combiner and the analog precoder to eliminate interference between multiple users.Finally,the digital combiner is designed by the MMSE criterion.