Joint rate maximization of downlink and uplink in NOMA SWIPT systems

Abstract

The combination of Non-orthogonal multiple access (NOMA) and Simultaneous wireless information and power transfer (SWIPT) is an emerging technology that can meet the requirements of spectral efficiency and energy efficiency. In this paper, we study the achievable rate maximization for jointly downlink and uplink network with power splitting-based SWIPT. We propose two different models. By using Single-Input Single-Output (SISO)-NOMA in conjunction with SWIPT, a joint uplink and downlink resource allocation scheme is proposed with the optimization objective to maximize the sum rate. We prove the objective function is strictly concave and found the optimal power splitting factor of each user. By using Multiple-Input Multiple-Output (MIMO)-NOMA in conjunction with SWIPT, we add timeslot allocation and propose a power splitting control and a timeslot allocation scheme. The optimization problem is divided into two subproblems to reduce solving complexity. In more detail, we first design the power splitting control scheme to maximize both the achievable rate and harvested energy in the downlink. Then timeslot optimization method is designed to improve the sum throughput. The simulation results show that a relatively high downlink rate can be achieved, while the required energy is simultaneously harvested by the users for the uplink.