FDD无蜂窝大规模MIMO系统CSI反馈及预编码研究  

Research on CSI feedback and precoding in FDD cell-free massive MIMO systems

作　　者：张德坤 白宝明[1] ZHANG Dekun;BAI Baoming(State Key Laboratory of Integrated Services Networks,Xidian University,Xi’an 710071,China;ZTE Corporation,Shenzhen 518055,China)

机构地区：[1]西安电子科技大学空天地一体化综合业务网全国重点实验室,陕西西安710071 [2]中兴通讯股份有限公司,广东深圳518055

出　　处：《电信科学》2024年第12期63-73,共11页Telecommunications Science

基　　金：国家重点研发计划项目(No.2021YFA000500)。

摘　　要：实现频分复用(frequency division duplexing,FDD)无蜂窝大规模多输入多输出(multiple input multiple output,MIMO)系统的下行系统容量最大化,关键在于设计既具有高成形增益又能强效抑制多用户间干扰的预编码矩阵,而精准的下行链路信道状态信息(channel state information,CSI)的获取则是计算预编码矩阵的基础。FDD制式由于上下行链路不具备完美互易性,故低开销、高精度的下行CSI获取是业界难题。为此,提出了一种基于共址空间用户簇的CSI测量和反馈方案,同时设计了联合簇级CSI反馈的两段式预编码优化方案。首先,基于上下行统计互易性计算获得等效下行空间相关性,利用用户反馈的信道质量和等效空间相关性联合构建了共址空间用户簇。其次,基于大尺度衰落特征和CSI导频端口能力约束,设计了CSI相干测量动态方案,以及共址空间簇的统计CSI反馈方案,显著地降低了反馈开销。最后,在CSI测量阶段通过簇间用户统计协方差矩阵设计了大尺度缓变干扰消除预编码,在下行调度阶段基于信号泄露噪声比(signal-toleakage-and-noise ratio,SLNR)算法设计了簇内实时多用户干扰消除预编码,二者级联构成每个用户的下行预编码优化权值。仿真结果表明,提出的CSI反馈优化方案相对于文献中主路径增益信息反馈策略降低反馈开销34%,两段式预编码优化方案相对于SLNR预编码提升FDD无蜂窝大规模MIMO频谱效率10.8%。For frequency division duplexing(FDD)cell-free massive multiple input multiple output(MIMO)systems,maximizing downlink capacity relies on designing a precoding matrix that achieves high beamforming gain and effectively suppresses multi-user interference.The accurate acquisition of downlink channel state information(CSI)is es sential for calculating precoding matrix.However,due to the imperfect reciprocity between uplink and downlink in FDD systems,securing low-overhead and high-precision downlink CSI remains an industry challenge.Therefore,a CSI measurement and feedback scheme on the basis of co-located spatial user clusters was proposed,along with a two-stage precoding optimization scheme that integrated cluster-level CSI feedback.Firstly,equivalent downlink spatial correlation was obtained based on the calculation of uplink and downlink statistical reciprocity,and co-located space user clusters were jointly constructed using the downlink channel quality and equivalent spatial correlation.Secondly,a dynamic CSI coherent measurement scheme was designed based on large-scale fading characteristics and CSI pilot port capacity constraints,and a statistical CSI feedback scheme for co-located space clusters was developed,significantly reducing feedback overhead.Finally,during the CSI measurement phase,large-scale slowly varying interference elimination precoding was designed using the statistical covariance matrix between cluster users.During the downlink scheduling phase,real-time multi-user interference elimination precoding within clusters was designed on the basis of the signal-to-leakage-and-noise ratio(SLNR)algorithm.The two were cascaded to form the optimized downlink precoding weight values for each user.Simulation results show that the proposed CSI feedback optimization scheme reduces the feedback overhead by 34%compared with the path gain information feedback strategy in the literature,and the two-stage precoding optimization scheme improves the FDD non-cellular massive MIMO spectral efficiency by 10.8%compar

关 键 词：频分复用无蜂窝大规模多输入多输出 共址空间用户簇 信道状态信息测量和反馈 两段式预编码 

分 类 号：TN929.5[电子电信—通信与信息系统]