基于延迟线组合调相的高能效自适应混合预编码方案

针对毫米波大规模多输入多输出系统采用混合预编码技术所带来的高功耗影响，基于延迟线组合调相器件设计了一种间接全连接型混合预编码系统结构，并提出一种自适应连接的混合预编码方案，可大幅减少与天线直连的调相器数量从而降低硬件造成的功耗损失。方案将编码矩阵的求解分为数字编码矩阵、模拟编码矩阵和开关组成的连接交换矩阵3个部分进行交替优化;提出一种基于互补正交投影矩阵的算法来解决模拟编码矩阵的优化;利用功率约束条件和最小二乘算法简化数字编码矩阵的求解;针对连接交换矩阵的离散组合优化问题，利用低复杂度的交叉熵算法进行优化。仿真结果表明，所提方案可以保证系统性能在接近纯数字预编码方案的同时有效提高系统的能量效率。

High energy efficiency adaptive hybrid precoding scheme based on delay line combined phase modulation

Aiming at the high-power consumption impact of millimeter-wave large-scale multiple-input-multiple-output systems using hybrid precoding techniques, an indirect fully-connected hybrid precoding system architecture is designed based on delay line combined phase modulator devices, and an adaptive connected hybrid precoding scheme is proposed, which can significantly reduce the phase modulators directly connected to the antenna and thus reduce the power loss caused by the hardware. The scheme divides the solution of the coding matrix into three parts for alternating optimization: the digital coding matrix, the analog coding matrix, and the connection exchange matrix composed of switches. An algorithm based on complementary orthogonal projection matrix is proposed to solve the optimization of the analog coding matrix; the power constraints and least squares algorithm are utilized to simplify the solution of the digital coding matrix; and the low-complexity cross-entropy algorithm is utilized for the optimization of discrete combinations of connected exchange matrices. Simulation results show that the proposed scheme can ensure system performance close to pure digital precoding scheme while effectively improving system energy efficiency.