大规模MIMO时分双工系统的鲁棒预编码设计

对于采用大规模MIMO技术的时分双工系统，天线互易误差会破坏上下行信道互易特性，大幅降低预编码算法下行传输性能。由于实际系统难以完全消除天线互易误差，该文以最大化各用户平均信泄噪比为目标，根据天线互易误差的统计特性，设计了对该误差具有鲁棒性的线性预编码算法。同时为了进一步降低用户接收端的等效噪声功率，该文还将该线性鲁棒预编码算法扩展为基于矢量扰动的非线性鲁棒预编码算法，并通过减格辅助技术降低其扰动矢量求解复杂度，使其更适用于大规模MIMO系统应用。计算机仿真结果表明在存在基站天线互易误差条件下，该文所提出的线性与非线性鲁棒性预编码算法的性能均优于传统预编码算法的性能。

Robust Precoding in Massive MIMO Time Division Duplex Systems

The downlink transmission performance of the massive MIMO Time Division Duplex (TDD) system is bottlenecked by the channel reciprocity errors called antenna reciprocity errors. Antenna reciprocity errors are hard to be calibrated completely in practical systems. In order to avoid the performance degradation of the downlink transmission, a linear robust precoding algorithm is proposed, which can maximize each users average Signal to Leakage and Noise Ratio (SLNR) by using the statistical characteristics of the antenna reciprocity errors. To further reduce the equivalent noise power of users, the linear robust precoding algorithm is improved into nonlinear robust precoding algorithm by vector perturbation. Lattice reduction aid is also used to reduce the complexity of the perturbation vector search, and make the nonlinear robust precoding algorithm be available for the massive MIMO. Simulation results show that the proposed linear and nonlinear robust precoding algorithms can achieve better performance than the traditional Zero Forcing (ZF) and SLNR precoding algorithms when antenna reciprocity errors exist.