Minimum Sum-Mean-Square-Error Frequency-Domain Pre-Coding for Downlink Multi-User MIMO System in the Frequency-Selective Fading Channel. - Qiyue Yu; Ji-Chong Guo; Shu-Ying Gao; Wei-Xiao Meng 001; Wei Xiang 001 (IEEE Trans. Wirel. Commun., 2017)