MmWave relay systems with robust hybrid transceiver designs under correlated channel estimation errors

Lei Zhao, Zhen Luo, Hongqing Liu, Xumin Pu, Quan Kuang

Abstract: In this paper, we incorporate mmWave systems with relay techniques to propose a hybrid transceiver design approach. The existing researches of hybrid transceiver designs mostly rely on accurate channel state information acquisitions. However, it is hard to avoid estimation errors in practice, which motivates us to propose a robust design based on imperfect channel estimations. We first design the fully digital processors and then decompose them into hybrid ones. An alternating algorithm is proposed to solve the fully digital processors by utilizing the relationship between the maximization of the upper bound of the averaged mutual information and the weighted minimum mean squared error problem. A decomposition algorithm with closed-form solutions is also proposed to obtain hybrid processors with analog-digital-analog structure at the relay terminal. Compared with related works, the proposed decomposition algorithm outperforms existing decomposition methods under imperfect CSI condition and the proposed hybrid design sacrifices certain complexity to achieve obvious performance improvements, which are illustrated by numerical simulations.