Energy-efficient Joint Beamforming Design for IRS-assisted MISO System

Intelligent reflective surface (IRS) is envisioned as a promising transmission technique for next-generation communication systems owing to its ability to reconfigure the wireless propagation environments. In this paper, we aim to maximize the energy-efficiency (EE) for an IRS-assisted downlink multiple-input single-output system. To solve the multi-variable non-convex optimization problem, a joint optimization of the transmit beamforming vector, power, and phase shift matrix at the IRS is performed with the help of the block coordinate descent (BCD) method. Presented simulation results demonstrate that the convergence of the BCD method is remarkably fast and the single iteration based solution has almost the same EE performance (less than 2.5%) as the iterative one. Meanwhile, the proposed scheme can achieve a 70.7% gain in EE when compared with the IRS-free counterpart.