In this letter, we propose to employ reconfigurable intelligent surfaces (RISs) for enhancing the D2D underlaying system performance. We study the joint power control, receive beamforming, and passive beamforming for RIS assisted D2D underlaying cellular communication systems, which is formulated as a sum rate maximization problem. To address this issue, we develop a block coordinate descent method where uplink power, receive beamformer and refection phase shifts are alternatively optimized. Then, we provide the closed-form solutions for both uplink power and receive beamformer. We further propose a quadratic transform based semi-definite relaxation algorithm to optimize the RIS phase shifts, where the original passive beamforming problem is translated into a separable quadratically constrained quadratic problem. Numerical results demonstrate that the proposed RIS assisted design significantly improves the sum-rate performance.

翻译：本文提出利用可重构智能表面（RIS）提升D2D底层系统性能。我们研究了RIS辅助D2D底层蜂窝通信系统中的联合功率控制、接收波束成形与无源波束成形问题，该问题被建模为和速率最大化问题。为解决此问题，我们开发了一种块坐标下降法，交替优化上行链路功率、接收波束成形器和反射相位偏移。随后，我们给出了上行链路功率与接收波束成形器的闭式解。进一步提出基于二次变换的半定松弛算法来优化RIS相位偏移，将原始无源波束成形问题转化为可分离的二次约束二次规划问题。数值结果表明，所提出的RIS辅助设计方案能显著提升系统和速率性能。