🤖 AI Summary
This paper addresses the sum-rate maximization problem in reconfigurable intelligent surface (RIS)-assisted device-to-device (D2D)-underlaid cellular networks, jointly optimizing uplink transmit powers, base station (BS) receive beamforming, and RIS passive phase shifts. It is the first work to integrate RIS into D2D-celullar spectrum sharing scenarios. A block coordinate descent (BCD)-based joint optimization framework is proposed: closed-form optimal solutions are derived for power allocation and BS receive beamforming; for the non-convex RIS phase optimization, an efficient algorithm combining quadratic transformation and semidefinite relaxation (SDR) is designed. The proposed method significantly reduces computational complexity. Numerical results demonstrate substantial sum-rate gains over RIS-free baseline schemes under typical system configurations, thereby validating the effectiveness and practicality of RIS for enhancing D2D-underlaid cellular networks.
📝 Abstract
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.