Power Minimization of STAR-RIS-Aided Underlay D2D-NOMA System With Energy Harvesting

Device-to-device (D2D) communication is the cutting-edge technology for the future Internet of Things (IoT) wireless networks. However, it encounters deployment challenges such as spectrum availability, latency, scalability, and energy efficiency. A simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS)-equipped non-orthogonal multiple access (NOMA) systems can mitigate these challenges by jointly optimizing the power allocation coefficients and the phases of low-cost passive STAR-RIS elements. Specifically, we focus on the power minimization of simultaneous wireless information and power transfer (SWIPT)-enabled D2D with STAR-RIS integrated downlink NOMA systems via jointly optimizing active beamforming design at AP and the power transmission in a D2D system. The problem is subject to minimum data rate requirements, transmission power constraint at AP, energy harvesting requirements, phase and amplitude constraint of each element, and power allocation coefficient for the user. To tackle the non-convex optimization problem, we adopt the disciplined concave-convex programming (DCCP) algorithm, which divides the non-convex problem into convex subproblems using a first-order Taylor series expansion in an alternative optimization approach. The simulation results validate the effectiveness of the proposed algorithm.