Multi-User Cooperative Non-Orthogonal Multiple Access Scheme With Hybrid Full/Half-Duplex User-Assisted Relaying

Abstract

This paper has investigated a downlink non-orthogonal multiple access (NOMA) cooperative scheme with user-assisted relaying, where near users are viewed as decode-and-forward (DF) relays operating full/half-duplex mode to assist multiple far users. Especially, the impact for the randomness of users location on the system performance has also been studied. Further, to overcome the zero diversity gain inherent to full-duplex (FD) operation, the direct link between a base station (BS) and each far user is exploited. The comprehensive performance analysis is conducted through the closed-form expressions in terms of outage probability, the diversity gain, system throughput, and ergodic sum rate. With respect to outage behavior, throughput, and ergodic sum rate, FD-based NOMA outperforms half-duplex (HD) NOMA in the lower signal-to-noise ratio (SNR) region. However, with the negative influence brought by residual loop-interference (LI), the advantage of FD NOMA scheme is not pronounced enough in the high SNR regime. Therefore, according to different SNR levels, we further propose a hybrid relaying scheme that switches opportunistically between the FD and HD modes. Afterward, the mode switching threshold is characterized such that the outage probability of each user is minimized. The simulation results confirm the correctness of our analysis and offer a significant guideline for system design in practice. INDEX TERMS User relaying, full-duplex, non-orthogonal multiplex access, outage probability, throughput, ergodic sum rate.

A Low-Complexity Framework for Joint User Pairing and Power Control for Cooperative NOMA in 5G and Beyond Cellular Networks

“…In addition, the adopted performance metric is the max-min achievable rate, which is known to be bandwidth-inefficient since the majority of resource is allocated to the user with poor channel gain to maintain fairness. A limited amount of works in the literature have formally studied the performance of multi-user C-NOMA [35]- [38]. In [35], [36], the authors studied the performance of C-NOMA in terms of outage performance.…”

“…A limited amount of works in the literature have formally studied the performance of multi-user C-NOMA [35]- [38]. In [35], [36], the authors studied the performance of C-NOMA in terms of outage performance. However, these works have either employed random or heuristic distance-based pairing, which limits the performance gains of C-NOMA.…”

Threshold-Based User-Assisted Cooperative Relaying in Beamspace Massive MIMO NOMA Systems

“…On the other hand, to improve the performance of the user-assisted CRS further in terms of outage probability and throughput, several studies investigated exploiting full/half-duplex MUT relaying in NOMA CRS [ 19 , 42 , 43 ]. In [ 19 ], two cooperative relaying schemes were proposed in a NOMA-based user-assisted CRS, namely, on/off full-duplex and on/off half-duplex, and a mechanism to decide whether cooperative relaying is necessary or not, and analyze the performance in terms of outage probability and throughput.…”

“…Guo et al. [ 43 ] investigated a NOMA-based user-assisted CRS in downlink where near MUTs are viewed as full/half-duplex decode-and-forward relays to support multiple far MUTs. Specifically, the impact of the randomness of MUT locations on the system performance was studied using stochastic geometry and evaluated in terms of outage probability [ 43 ].…”

Joint Integer-Forcing Precoder Design for MIMO Multiuser Relay System

“…Cooperative data transmission has received much research attention in recent years. By equipping these networks with one or more relays, cooperative communication can enhance the coverage, reliability, power efficiency, and capacity of wireless networks [1]- [5]. According to the re-transmission mode of the relay, various cooperative transmission protocols can be used, such as the amplify-and-forward (AF) and decode-and-forward (DF) protocols.…”