Cooperative Non-orthogonal Multiple Access With Simultaneous Wireless Information and Power Transfer

Accepted by IEEE Journal on Selected Areas in Communications (JSAC

Power splitting versus time switching based cooperative relaying protocols for SWIPT in NOMA systems

Non-orthogonal multiple access (NOMA) along with wireless power transfer have recently been adapted to cooperative communications for 5G and beyond wireless networks. This paper investigates NOMA based cooperative relaying wireless- powered networks (CRWPNs) where, decode-and-forward (DF) relaying and successive interference cancellation are both employed at a wireless-powered intermediate node. For simultaneous wireless information and power transfer (SWIPT), power-splitting relaying (PSR) and time switching-based relaying (TSR) protocols are considered in the NOMA based CRWPN. As a result, the combination of cooperative relaying power domain NOMA network and PSR and TSR protocols is proposed in this paper. The outage performance and ergodic rate of both protocols are analysed for evaluation of the impacts of energy harvesting (EH) time, EH efficiency, power splitting ratio, source data rate, and the distance between the nodes. In addition, two delay limited transmission (DLT) and delay tolerant transmission (DTT) modes are considered in this network model to investigate the throughput and ergodic rate of the system according to the source transmission rate. It is shown that the cooperative relaying NOMA (CRNOMA) scheme achieves a lower outage probability when compared to the conventional orthogonal multiple access (OMA) schemes. Additionally, the PSR outperforms the TSR in both low and high signal-to-noise ratio (SNR) regions in terms of throughput, ergodic rate and energy efficiency. For instance, the outage probability of CRNOMA for both PSR and TSR in SNR range of from -10 dB to +20 dB (i.e. a low SNR region) decreases gradually but not linearly. However, in SNR range of from +20 dB to +40 dB (i.e. a high SNR region), the outage probability of CRNOMA for both PSR and TSR decreases quickly. Furthermore, the energy efficiency is shown to be considerably enhanced with the employment of EH for CRNOMA. Finally, the impacts of the distance between the nodes on the performance and a comparison between two scenarios of having and without having direct links are evaluated

Wireless Powered Cooperative Relaying using NOMA with Imperfect CSI

The impact of imperfect channel state (CSI) information in an energy harvesting (EH) cooperative non-orthogonal multiple access (NOMA) network, consisting of a source, two users, and an EH relay is investigated in this paper. The relay is not equipped with a fixed power source and acts as a wireless powered node to help signal transmission to the users. Closed-form expressions for the outage probability of both users are derived under imperfect CSI for two different power allocation strategies namely fixed and dynamic power allocation. Monte Carlo simulations are used to numerically evaluate the effect of imperfect CSI. These results confirm the theoretical outage analysis and show that NOMA can outperform orthogonal multiple access even with imperfect CSI.Comment: 6 pages, 6 figures, accepted in IEEE GLOBECOM 2018 NOMA Worksho

Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks

Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be promising in the fifth generation (5G) wireless networks. H-CRANs enable users to enjoy diverse services with high energy efficiency, high spectral efficiency, and low-cost operation, which are achieved by using cloud computing and virtualization techniques. However, H-CRANs face many technical challenges due to massive user connectivity, increasingly severe spectrum scarcity and energy-constrained devices. These challenges may significantly decrease the quality of service of users if not properly tackled. Non-orthogonal multiple access (NOMA) schemes exploit non-orthogonal resources to provide services for multiple users and are receiving increasing attention for their potential of improving spectral and energy efficiency in 5G networks. In this article a framework for energy-efficient NOMA H-CRANs is presented. The enabling technologies for NOMA H-CRANs are surveyed. Challenges to implement these technologies and open issues are discussed. This article also presents the performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure