Reconfigurable intelligent surface (RIS) is widely accepted as a potential technology to assist in communication between base stations (BSs) and users in edge areas. We study the energy efficiency of a RIS-assisted multi-cell communication system with a realistic RIS power consumption model. With the goal of maximizing the energy efficiency of the system, we optimize the transmit beamforming vectors at the BS and the RIS phase shift matrix by a proposed alternative optimization algorithm. First, the transmit beamforming vector is optimized by solving the transformed weighted minimum mean square error (WMMSE) problem. Subsequently, to solve the inconvenience incurred by the discrete relationship between the RIS reflecting unit power consumption and its discrete phase shift, we use a continuous function to approximate their relationship. With this approximation, we can use the majorization minimization (MM) technique to optimize the continuous RIS phase shifts, and then quantize the obtained phase shifts to discrete ones. Simulation results demonstrate that the energy efficiency of the system is effectively optimized by the proposed algorithm.

可重构智能表面（RIS）被广泛认为是一种有助于边缘区域基站（BS）和用户之间通信的潜在技术。我们使用现实的 RIS 功耗模型研究 RIS 辅助多小区通信系统的能源效率。为了最大化系统的能量效率，我们通过提出的替代优化算法优化了 BS 处的发射波束成形向量和 RIS 相移矩阵。首先，通过求解变换后的加权最小均方误差（WMMSE）问题来优化发射波束成形矢量。随后，为了解决反映单位功耗的RIS与其离散相移之间的离散关系带来的不便，我们使用连续函数来近似它们的关系。通过这种近似，我们可以使用主化最小化（MM）技术来优化连续的RIS相移，然后将获得的相移量化为离散相移。仿真结果表明，该算法有效优化了系统的能源效率。