混合预编码器的内在关联机制与结构优化

In the 5G millimeter-wave communication systems, hybrid precoding is one of the key technologies to realize large-scale MIMO transceiver structure，and its structure affects the system hardware cost and service quality. Focusing on improving the accuracy and decrease the computational complexity of hybrid precoder design, much research has been carried out. However, all the research does not consider the relationship between digital baseband precoding and analog phase shifter and structure optimization, which is the foundation to design hybrid precoder and the theoretical basis to further reduce system hardware cost. Based on the above issues, according to the channel sparsity of mmWave large-scale MIMO system, this project will research its internal association mechanism and structure optimization using the theories, such as compressed sensing, matrix decomposition and optimization, and explore the relationship between the sparsity of channel matrix and the numbers of required RF links and feasible parallel data streams, optimize the structure of hybrid precoder, which benefits to reduce the hardware cost and power consumption of hybrid precoder and its support circuits. Furthermore, evaluate the found internal association mechanism and the proposed schemes, and construct the fundamental theoretical system for hybrid precoder design of massive MIMO systems.

在5G毫米波通信系统中，混合预编码是实现大规模MIMO收发结构的关键，混合预编码器的结构关系到系统的硬件成本和服务质量。已有研究主要集中于如何提高混合预编码器的精确度和降低算法复杂度，并没有考虑数字基带预处理部分与模拟相移器之间的关联和结构优化，而这正是混合预编码器设计的基础，也是进一步降低系统硬件成本的理论依据。基于此，本申请项目利用毫米波大规模MIMO信道的稀疏特性，采用压缩感知、矩阵分解以及最优化理论对混合预编码器的内在关联与结构优化机制进行研究，探索所需射频链路数和能并行传输的数据流支路数与信道稀疏特性之间的关系，试图对混合预编码器的结构进行优化，进一步降低混合预编码器及其配套电路的硬件成本和功率消耗。同时，对所提的内部转换机制和结构优化策略进行性能评估，构建混合预编码器优化设计的理论体系。

混合预编码是5G通信系统降低硬件成本和功率消耗的有效途径，也是毫米波大规模多输入多输出(MIMO)系统得以广泛应用的理论基础。本项目对混合预编码策略展开深入研究，力图提出低实现复杂度、高频谱效率的混合预编码算法。目前主要完成以下工作：(1) 通过对阵列响应矩阵进行奇异值分解，选取一些特征值较大的特征向量与全数字预编码矩阵进行相关运算，最相关特征向量的相位信息用来构建模拟预编码器的相位，从而完成系统的混合预编码器的设计；(2) 通过对全数字预编码矩阵的奇异值分解，从左分解矩阵中提取模拟相移器的相位信息，从而快速完成系统的混合预编码设计；(3)针对数据流数与射频链路数相等的网络场景，提出一种性能较好、复杂度较低的等效信道混合预编码设计方法。相对已有的正交匹配混合预编码算法，所提算法的复杂度得到降低，通过直接对全数字预编码矩阵进行处理获得模拟预编码的相位信息有利于系统频谱效率的提高。

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