Energy Efficiency Optimization for NOMA With SWIPT

Jie Tang,Jingci Luo,Emad Alsusa,Mingqian Liu,Gaojie Chen,Jonathon A Chambers,Daniel K C So,Kai-Kit Wong

doi:10.1109/jstsp.2019.2898114

Abstract

The combination of simultaneous wireless information and power transfer (SWIPT) and non-orthogonal multiple access (NOMA) is a potential solution to improve spectral efficiency and energy efficiency (EE) of the upcoming fifth generation (5G) networks, especially in order to support the functionality of the Internet of things (IoT) and the massive machine-type communications (mMTC) scenarios. In this paper, we investigate joint power allocation and time switching (TS) control for EE optimization in a TS-based SWIPT NOMA system. Our aim is to optimize the EE of the system whilst satisfying the constraints on maximum transmit power budget, minimum data rate, and minimum harvested energy per terminal. The considered EE optimization problem is neither linear nor convex involving joint optimization of power allocation and time switching factors and, thus, is extremely difficult to solve directly. In order to tackle this problem, we develop a dual-layer algorithm where Dinkelbach method is employed both in the inner layer to optimize the power allocation and in the outer layer to control the time switching assignment. Furthermore, a simplified but practical special case with equal time switching factors in all terminals is considered. Numerical results validate the theoretical findings and demonstrate that significant performance gain over orthogonal multiple access scheme in terms of EE can be achieved by the proposed algorithms in a SWIPT-enabled NOMA system.

Highlights

The exponential growth of wireless data services driven by mobile internet and connected devices has triggered theThis paper was presented in part at the IEEE Global Communications Conference (GLOBECOM), Abu Dhabi, UAE, 2018
Compared to the conventional orthogonal multiple access (OMA) approach, our findings have illustrated that significant EE gain can be achieved by our proposed algorithm, and this has confirmed the advantages of integrating simultaneous wireless information and power transfer (SWIPT) into non-orthogonal multiple access (NOMA) systems
The channel noise is considered as AWGN with power σ2 = 0.001W ; the drain efficiency of the power amplifier ζ is set to 38% whereas the energy harvesting (EH) efficiency is taken to be η = 10%; the bandwidth of the system is set to B = 1M Hz [44]

Summary

Introduction

The exponential growth of wireless data services driven by mobile internet and connected devices has triggered theThis paper was presented in part at the IEEE Global Communications Conference (GLOBECOM), Abu Dhabi, UAE, 2018. The available spectrum resources are far from enough to support the communication systems with the increasing demand for high data rate. This trend makes spectral efficiency (SE) to be the main performance indicator for the design and optimization of wireless systems, but at the same time constitutes to ever-rising network power consumption which has severe implications in terms of both economic and ecological costs, and energy saving has been recognized as an urgent issue worldwide. Non-orthogonal multiple access (NOMA) can further improve the SE as each subcarrier is allowed to serve multiple terminals at the same time [3], and it has received considerable attention as a promising candidate for 5G [4]–[9]. Similar results for EE optimization problem were observed in [11] for a downlink single input single output (SISO) NOMA system and in [13] for heterogeneous NOMA networks

Objectives

Results

Conclusion