This paper considers an intelligent reflecting surface (IRS) aided multiple-input single-output communication system, where statistical channel state information (CSI) is exploited for transmit beam-forming and IRS beamforming. A tight upper bound is derived for the ergodic capacity of the system. Based on which, the joint optimization of transmit beam and IRS beam are studied. Depending on whether a line-of-sight path exists between the access point and user, two different cases, namely, Rician fading and Rayleigh fading, are separately treated. Specifically, for the Rician fading case, an iterative algorithm is proposed, which is guaranteed to converge. For the Rayleigh fading case, closed-form designs are obtained for the transmit beam and IRS beam. Simulation results show the proposed beamforming scheme achieves similar performance as the benchmark algorithm requiring instantaneous CSI.

本文考虑了一种智能反射面（IRS）辅助的多输入单输出通信系统，其中利用统计信道状态信息（CSI）来进行发射波束成形和IRS波束成形。得出系统遍历容量的上限。在此基础上，研究了发射光束与IRS光束的联合优化。根据接入点和用户之间是否存在视线路径，分别处理两种不同的情况，即Rician衰落和Rayleigh衰落。具体来说，针对Rician衰落情况，提出了一种迭代算法，可以保证收敛。对于瑞利衰落情况，针对发射波束和IRS波束获得了封闭形式的设计。