Research On Dynamic Subarrays Architecture For Millimeter Wave Massive MIMO Hybrid Precoding

With the development of the information age,people's digital entertainment life is becoming more and more abundant.Smart phone improves people's quality of life,while it also put forward new requirements for wireless data services.In the era of fifth-generation mobile communications system(5G),it is not only necessary to provide a peak transmission speed that is several tens of times that of fourthgeneration mobile communications system(4G),but also to ensure a data transmission delay of milliseconds.The current low-frequency communications system can no longer meet the new requirements of wireless communications.Compared with the current commercial wireless communication system,more communication bands can be provided with the millimeter-wave(mm Wave)frequency band,which may bring the wireless communication into a new era.The problem of millimeter-wave propagation serious loss can be compensated by a largescale antenna arrays,which makes millimeter-wave massive MIMO technology becoming the one of most important technologies for 5G networks and nextgeneration wireless networks.Large-scale antenna arrays will come with relatively high hardware costs,energy consumption and computational complexity.Compared with the traditional fully digital precoding scheme,hybrid precoding is a scheme to balance performance and hardware overhead.However,the traditional hybrid precoding generally uses a fully connected antenna architecture where each radio frequency(RF)chain is connected to all antennas,so that the number of phase shifters(PS)and radio frequency adders significantly increase under the condition of large-scale antennas.Therefore,fully connected architecture will also cause high hardware costs and power consumption in the situation of large-scale antennas.To overcome the problem of the fully connected architecture,this article focuses on the hybrid precoding scheme with the partially connected architecture.The partially connected architecture can effectively solve the problem of excessive number of phase shifters and no longer needs radio frequency adders,hence the hardware cost and power consumption are effectively reduced compared to the fully connected architecture.Partially connected architecture can be further divided into fixed subarrays architecture and dynamic subarrays architecture.In the fixed subarrays,each radio frequency chain is connected to a fixed number of antenna subsets and there is no intersection between different antenna subsets.However,in the dynamic subarray architecture,the radio frequency chain and the antenna can be dynamically connected through a low-power switch network,hence the corresponding antenna subset can be adaptively divided according to the channel state information.This article firstly designs a hybrid precoding algorithm for a single user mm Wave MIMO system and proposes a hybrid precoding scheme based on maximizing mutual information.On this basis,an algorithm of antenna subset division based on a clustering algorithm is designed,which abstracts the antenna division as an antenna clustering problem.Comparing to the fixed subarrays precoding scheme,the proposed algorithm has a great improvement of performance and guarantees the low complexity.Although the scenario of single user with multi-data in mm Wave system can increase the rate of system,mm Wave MIMO systems are also an important method to improve system capacity and effectively achieve multi-user access.Next,this paper proposes a hybrid precoding based on fractional programming under multi-user millimeter wave MIMO system.The difference from the current multi-user dynamic subarrays scheme is that user fairness is taken as an indicator into consideration and the weighted sum-rate is designed to ensure the fairness between users when designing the optimization goal.The proposed algorithm has obvious performance improvement over the current scheme under the condition of one-bit quantization precision phase shifter.