Heterogeneous-IRS: A Green IRS Structure With Dynamically and Statically Tunable Elements

Recently, intelligent reflecting surface (IRS) has received significant attention due to its ability to smartly reconfigure the wireless environment. However, in practical implementation, the power consumption of the conventional IRS could be prohibitive with the large number of reflecting elements and control circuits employed. To tackle this problem, in this letter, we propose a green heterogeneous-IRS (HE-IRS) structure consisting of both dynamically tunable elements (DTEs) and statically tunable elements (STEs). Compared to the conventional IRS comprising only DTEs, the HE-IRS provides a better trade-off between performance and power consumption by integrating power-free STEs. To show the efficiency of the proposed HE-IRS, we apply it in a multi-input multi-output system and formulate a joint base station precoding, HE-IRS beamforming and user equipment (UE) decoding optimization problem. Furthermore, we propose a two-stage algorithm to solve it. Simulation results show that with the prior information of the UE location area, the HE-IRS can achieve a competitive spectral efficiency as that of the conventional IRS but with much lower power consumption.