Channel Acquisition And Adaptive Transmission In Millimeter Wave Wireless Communications

Millimeter-wave communication is defining a new era of wireless communication.The millimeter-wave band provides larger bandwidth for higher-rate communications than the frequency bands currently used in commercial wireless systems.Compared with traditional multi-input multiple-output(MIMO)systems,the hardware constraints and power consumption in millimeter-wave MIMO systems make it difficult to equip each antenna with an RF chain.Therefore,the digital/analog hybrid precoding architecture has become a choice in millimeter wave MIMO system to compromise the complexity of hardware and system performance.which also brings new serious challenges to the channel estimation and adaptive beamforming in millimeter-wave communication.In view of these problems,this paper carries out channel acquisition and adaptive transmission research in millimeter wave communication.The main work and innovations of this thesis are summarized as follows:Firstly,the propagation characteristics of millimeter-wave channel are analyzed from the aspects of path loss,blocking effect and space characteristics.The digital/analog hybrid MIMO precoding architecture for millimeter-wave system is introduced and analyzed,and the millimeter-wave channel acquisition and beam-forming techniques under the hybrid architecture are analyzed,which provides the theoretical basis and con-trast for the algorithm design and performance analysis of the following chapters.Secondly,the precoding problem under the millimeter-wave digital/analog hybrid architecture is studied.A method of hybrid precoding optimization of millimeter-wave based on analog beam quantization codebook is proposed,and an effective algorithm is proposed to solve the power minimization problem of digital/analog communication system.The numerical simulation shows that the proposed algorithm can approximate the performance of the optimal method of exhaustive search.Thirdly,the hybrid precoding and channel acquisition in the millimeter-wave multiuser system are s-tudied.A method for millimeter-wave multi-user hybrid precoding and channel acquisition based on beam scanning is proposed.With the objective of maximizing the sum rate of millimeter-wave downlink multi-user MISO communication system,the joint optimization design of analog and digital precoding is realized,and the feedback and quantization scheme for millimeter wave system are designed according to the sparse char-acteristic of millimeter wave channel.The simulation results show that the proposed scheme can obtain near optimal system performance under limited feedback.The method only needs to obtain partial channel state information,which is more implementable in practical application.Finally,the hybrid precoding and channel acquisition techniques in broadband millimeter-wave systems are studied,A multiuser hybrid precoding method with partial channel state information in OFDM-based broadband millimeter-wave systems is proposed.According to the space characteristics of each subcarrier channel,the limited feedback is designed to reduce the feedback load.And in view of the high complexity of the original algorithm problem,the method of subcarrier grouping optimization and subcarrier power al-location is proposed,which can hardly affect the performance while can significantly reduce the complexity of the algorithm.The simulation results show that the proposed method can effectively solve the problem of hybrid precoding and channel acquisition in broadband millimeter wave system.