An Efficient Design for NOMA-Assisted MISO-SWIPT Systems with AC Computing

We consider a multiple-input single-output simultaneous wireless information and power transfer (MISO-SWIPT) system, where a power-splitting protocol is employed at users near the base station (BS) to provide both energy harvesting (EH) and information decoding. For the considered system, it is of practical interest to adopt non-orthogonal multiple access (NOMA) to improve the network spectral efficiency, while still meeting the EH requirements. In addition, an alternating current computing (ACC) logic is incorporated into EH receivers to directly use the wirelessly harvested AC power, which in turn achieves higher energy efficiency than traditional direct current computing (DCC). We formulate a problem of maximizing the spectral efficiency subject to the constraints of quality-of-service for the individual user, EH requirements, and BS's maximum transmit power, where the beamformers and PS ratios are jointly optimized. To achieve an efficient solution to this nonconvex problem, we propose an iterative algorithm based on the inner approximation (IA) framework, where the approximate convex problem solved in each iteration can be cast as a second-order-cone program with convergence guaranteed. To further simplify the problem design, we propose a zero-forcing beamforming-based NOMA approach to partially eliminate interference, which has the potential to significantly reduce the number of variables. The extensive numerical results are presented to demonstrate the effectiveness of the proposed algorithms, compared with the baseline schemes.