Intelligent Reflecting Surface-Assisted mmWave Communication Exploiting Statistical CSI
Fan Yang, Jun-Bo Wang, Hua Zhang, Chuanwen Chang, Julian Cheng
Abstract
Intelligent reflecting surface (IRS) is a new technique to improve the ergodic capacity in wireless networks. IRS consists of a large number of passive elements which digitally manipulate electromagnetic waves, and thus can act as a passive precoder in the communication. This paper introduces the IRS to millimeter wave (mmWave) multiple-input-multiple-output (MIMO) systems. Specifically, we consider a joint design of hybrid precoders at the base station (BS) and the passive precoder at the IRS to maximize the ergodic capacity of the system. In particular, since the instantaneous channel state information (CSI) of the BS-IRS link and the IRS-user link is challenging to obtain in practice, the statistical CSI is exploited for the joint hybrid and passive precoder design. However, such a design problem is challenging to solve due to the non-convexity. Thus, the block-coordinate-descent based algorithms are proposed to solve the problem efficiently. Simulation results demonstrate that, compared with the traditional systems without IRSs, the joint design of hybrid and passive precoding improves the ergodic capacity significantly. The results also show that adding some low-cost reflector elements at the IRS can help reduce the number of high-cost RF chains in the BS of the IRS-assisted mmWave MIMO systems.