Reconfigurable Intelligent Surface Empowered Underlaying Device-to-Device Communication

Reconfigurable intelligent surfaces (RIS) are a new and revolutionary technology to achieve spectrum-, energy- and cost-efficient wireless networks. This paper studies the resource allocation for RIS-empowered device-to-device (D2D) communication underlaying a cellular network, in which an RIS is employed to enhance desired signals and suppress interference between paired D2D and cellular links. We maximize the sum rate of D2D users and cellular users by jointly optimizing the resource reuse indicators, the transmit power and the RIS's passive beamforming. To solve the formulated non-convex problem, we first propose an efficient user-pairing scheme based on relative channel strength to determine the resource reuse indicators. Then, the transmit power and the RIS's passive beamforming are jointly optimized by an iterative algorithm, based on the techniques of alternating optimization, successive convex approximation, Lagrangian dual transform and quadratic transform. Numerical results show that the proposed design outperforms the traditional D2D network without RIS.

I. Introduction

Device-to-device (D2D) communication underlaying cellular networks, which allows a device to communicate with its nearby device over the licensed cellular bandwidth, is recognized as a promising technology in future networks due to its advantages such as high spectrum efficiency, high energy efficiency (EE) and low transmission delay [1]. Interference management is the most important challenge for underlaying D2D communication. The D2D link and the cellular link operating in the same licensed band interfere with each other severely [2], and the interference needs to be carefully suppressed via efficient interference management [3] and resource allocation [4].