Hybrid Precoding For Millimeter-wave MIMO System

With the rapid growth of wireless data service and the diversification of data forms,people have put forward higher requirements on communication transmission rate and communication quality.However,the scarcity of spectrum resources has become a key factor restricting the development of wireless communication.In order to solve the current shortage of spectrum resources,millimeter wave communication and Massive Multiple Input Multiple Output(Massive MIMO)systems have been proposed and recommended to enter 5G mobile standard.On the one hand,millimeter wave communication has a wider range of available bandwidth,which can lead to higher data transmission rates.On the other hand,due to the small physical size of the antenna under millimeter wave communication,the large antenna array can be integrated into the transceiver to effectively compensate for the path loss caused by millimeter wave communication.Therefore,millimeter wave communication and Massive MIMO technology are regarded as one of the core solutions of the fifth generation mobile communication system.This paper mainly focuses on the technical research on the mixed precoding design and energy efficiency of millimeter wave Multiple Input Multiple Output(MIMO)system.In this paper,a low complexity hybrid precoding algorithm based on truncation SVD decomposition is proposed for millimeter wave MIMO point-to-point communication system.In order to solve the problem of energy efficiency,an analog precoder mixed connection structure is proposed to balance power consumption and spectral efficiency.The main work of this paper is as follows:Firstly,this paper introduces the research background and characteristics of millimeter wave MIMO system,and briefly introduces the research status of millimeter wave MIMO system,analyzes the existing problems in millimeter wave communication and provides solutions.Secondly,this paper introduces the MIMO system and millimeter wave system in detail,and introduces the traditional precoding methods,including dirty paper coding and zero-forcing precoding.Then the digital precoding technology and analog precoding technology commonly used in traditional communication frequency band are introduced.Due to the limited application of the two in the millimeter wave MIMO system model,a hybrid precoding method which is more suitable for the system is introduced.Thirdly,the hybrid precoding design of millimeter wave MIMO point-to-point communication system is studied.Due to the high complexity of existing hybrid precoding methods,it is necessary to find a hybrid precoding method to reduce the complexity of practical applications.In this paper,a hybrid precoding scheme is designed to optimize spectral efficiency.Since the optimization target is non-convex,the optimization target is further converted into the subspace generated by the analog precoder and the subspace generated by the full digital precoder.On this basis,this paper proposes a low-complexity hybrid precoding algorithm based on truncated SVD decomposition,and analyzes and proves the effectiveness of the algorithm in principle.The calculation shows that the complexity of this method is only 1%of that of the orthogonal matching tracking algorithm under certain circumstances.Simulation results show that the spectral efficiency of the proposed method is similar to that of the all-digital optimal precoder in all cases,and is superior to the orthogonal matching tracking algorithm.Finally,the structure design of analog precoder under millimeter wave MIMO point-to-point communication system is studied.Based on this,a regular mixed connection structure for analog precoder is proposed.Based on this structure,fully connected structure and partially connected structure can be regarded as special cases,so the analysis of mixed connection structure can be extended to fully connected structure and partially connected structure.In addition,the structure has the advantage of realizing distributed antenna array system.The simulation results show that the spectrum efficiency of the mixed structure is between the fully connected structure and the partially connected structure,but because the scale of the phase-shifting network is reduced,compared with the fully connected structure,the energy efficiency of the system is greatly improved.