Joint Beamforming and Power-Splitting Power Splitting Control in Downlink Cooperative SWIPT NOMA Systems
Abstract: This paper investigates the application of simultaneous wireless information and power transfer (SWIPT) to cooperative non non-orthogonal orthogonal multiple access (NOMA). A new cooperative multiple multiple-input single-output output (MISO) SWIPT NOMA protocol is proposed, where a userr with a strong channel condition acts as an energyenergy harvesting (EH) relay by adopting power splitting (PS) scheme to help a user with a poor channel condition. By jointly optimizing the PS ratio and the beamforming vectors, we aim at maximizing the data rate rate of the “strong user” while satisfying the QoS requirement of the “weak user”. To resolve the formulated nonconvex problem, the semidefinite relaxation (SDR) technique is applied to reformulate the original problem, by proving the rank rank-one optimality. And d then an iterative algorithm based on successive convex approximation (SCA) is proposed for complexity reduction, which can at least attain its stationary point efficiently. In view of the potential application scenarios, e.g., Internet of Things (IoT), tthe single-input single-output output (SISO) case is also studied. The formulated problem is proved to be strictly unimodal with respect to the PS ratio. Hence, a golden section search (GSS) based algorithm with closed-form closed form solution at each step is proposed to find d the unique global optimal solution. It is worth pointing out that the SCA method can also converge to the optimal solution in SISO cases. In the numerical simulation, the proposed algorithm is numerically shown to converge