Research On Hybrid Precoding For Millimeter Wave Massive MIMO Systems

Millimeter-wave massive MIMO technology can significantly improve spectrum utilization and enhance bandwidth,and has become one of the key research technologies for 5G communication systems.However,due to the existence of a large number of antenna arrays in the system,this inevitably increases the complexity of the system and the power consumption of the equipment,which has a certain impact on the performance of the system,and also limits the development of millimeter-wave massive MIMO technology to a certain extent.In this regard,based on the principle of hybrid precoding,with the goal of maximizing the achievable sum rate of the system,a novel hybrid precoding technique for millimeter-wave massive MIMO systems is proposed.The main research contents and work are as follows:(1)For a fully-connected single-user millimeter-wave massive MIMO system,a hybrid precoding scheme based on an improved Orthogonal Matching Pursuit(OMP)algorithm is proposed.Firstly,in view of the problem of too many iterations in the basic OMP algorithm,inspired by the idea of multi-step size,the most optimal columns equal to the number of RF chains are taken from the array response matrix to construct an analog precoding matrix.Secondly,aiming at the high complexity of the inversion operation in the basic OMP algorithm,the formulated objective function to be optimized is approximated by jointing Holder(5)(5)inequality and Schatten norm through numerical formula derivation,so as to obtain the optimal digital precoding matrix.The simulation results show that the proposed modified OMP scheme effectively reduces the computational complexity,and the system performance is better when the gap between the number of data streams and the number of RF chains is small.(2)For a partially-connected multi-user millimeter-wave massive MIMO system,a hybrid precoding scheme based on the artificial bee colony(ABC)algorithm is proposed.Firstly,the classic zero-forcing precoding is firstly adopted in the digital domain,and then the analog precoding matrix is separately designed to satisfy the condition of maximizing the achievable sum rate of the system.And combined with the idea of ABC,the hybrid precoding design problem is equivalent to a random optimization problem for obtaining the optimal precoding matrix.Secondly,considering that the traditional artificial bee colony algorithm has a bad balance in exploration and exploitation capabilities,a solution based on crossover of global ABC algorithm is proposed.Through theoretical analysis and simulation results,it is shown that,compared to the traditional algorithms,the proposed algorithm has superior in the system sum rate and convergence performance.