Full-duplex Non-orthogonal Multiple Access Research Articles

Performance analysis of power-efficient IRS-Assisted full duplex NOMA systems

In this paper, we utilize intelligent reflecting surfaces (IRSs) in full-duplex (FD) systems to enhance diversity gain and system performance. The issue of self-interference in FD systems causing an outage floor is addressed. We propose a beamforming (BF) method that mitigates this effect, even when there is no direct channel between the source and the far user in non-orthogonal multiple access (NOMA) systems. We examine two designs, named fixed antenna mode (FAM) and adaptive antenna mode (AAM), for K decode-and-forward (DF) FD near users in a Rayleigh fading environment. To improve system performance, we employ joint antenna mode and near user selection techniques in IRS-NOMA systems. We evaluate the performance of the proposed schemes and derive closed-form expressions for outage probability and ergodic capacity, which are validated through simulations. The results demonstrate that the proposed scheme achieves additional spatial diversity gain through the use of the IRS structure and antenna mode selection at the relay nodes. Furthermore, the new BF technique improves power efficiency compared to conventional FD NOMA structures, and the analysis can be extended to 6G Massive MIMO systems using machine learning algorithms, which are applicable for millimeter wave channels.

Sum-Rate Maximization for RIS-Aided Full-Duplex Non-Orthogonal Multiple Access Networks: Joint Passive Beamforming and Resource Allocation

Sum-Rate Maximization for RIS-Aided Full-Duplex Non-Orthogonal Multiple Access Networks: Joint Passive Beamforming and Resource Allocation

A novel resource allocation scheme for full-duplex NOMA systems with power splitting-based SWIPT

This paper introduces novel resource allocation (RA) algorithms for optimizing wireless network performance, focusing on a full-duplex (FD) base station (BS) employing non-orthogonal multiple access (NOMA) technology. Motivated by the intriguing trade-off introduced by the simultaneous wireless information and power transfer (SWIPT) scheme, in which achievable data rates are sacrificed to enhance harvested energy, this study aims to quantify the delicate equilibrium between two vital aspects meticulously: the overall achievable data rate facilitated by NOMA and FD technologies and the energy harvested via the SWIPT approach. Specifically, our focus is on jointly optimizing the enhancement of both data rate and harvested energy for downlink (DL) users where a multi-objective optimization approach is developed in the proposed RA algorithm to study the existing trade-off between these conflicting objective functions. This problem optimizes the power allocation for both the BS and the users, allocating subcarriers, and optimizing the power splitting factor for SWIPT scheme. We developed efficient iterative solutions for the intended RA problems because they involve complex mixed-integer nonlinear optimization challenges that are generally difficult to solve. The effectiveness of the proposed RA framework is demonstrated using simulation results. These results investigate whether FD MC-NOMA systems, enabled by the proposed RA algorithms, provide a significant increase in system throughput compared to both conventional half-duplex (HD) multicarrier orthogonal multiple access (MC-OMA) systems and HD MC-NOMA systems, as well as other baseline methods. The results also demonstrate that our proposed scheme allows for a greater power harvest than the OMA-FD configuration and other baseline schemes.

Performance Analysis of Multihop Full-Duplex NOMA Systems with Imperfect Interference Cancellation and Near-Field Path-Loss.

Outage probability (OP) and potential throughput (PT) of multihop full-duplex (FD) nonorthogonal multiple access (NOMA) systems are addressed in the present paper. More precisely, two metrics are derived in the closed-form expressions under the impact of both imperfect successive interference cancellation (SIC) and imperfect self-interference cancellation. Moreover, to model short transmission distance from the transmit and receive antennae at relays, the near-field path-loss is taken into consideration. Additionally, the impact of the total transmit power on the performance of these metrics is rigorously derived. Furthermore, the mathematical framework of the baseline systems is provided too. Computer-based simulations via the Monte Carlo method are given to verify the accuracy of the proposed framework, confirm our findings, and highlight the benefits of the proposed systems compared with the baseline one.

WMMSE Resource Allocation for FD-NOMA

Resource allocation in interference-limited systems is a key enabler for beyond 5G (B5G) technologies, such as multi-carrier full duplex non-orthogonal multiple access (FD-NOMA). In FD-NOMA systems resource allocation is a computation-intensive non-convex problem due to the presence of strong interference and the integrality condition on channel allocation. In this letter, we propose an iterative algorithm based on the combination of channel and power allocations aimed at the minimization of the weighted mean square error, which converges to a feasible allocation of the original problem. Experimental results show that the proposed algorithm has lower complexity than other state-of-the-art solutions for the same problem. Moreover, the presented results assess the validity of our approach showing performance close to the theoretical optimum.

Energy Efficiency Maximization of Full-Duplex NOMA Systems With Improper Gaussian Signaling Under Imperfect Self-Interference Cancellation

This work addresses the energy efficiency maximization for a downlink cooperative full-duplex non-orthogonal multiple access (FD-NOMA) system in the presence of imperfect self-interference cancellation. We consider the case where users adopt improper Gaussian signaling (IGS) for their transmission and consequently derive the achievable rate of each link in the cooperative system. We jointly optimize the power allocation at the base-station and the IGS circularity coefficients of the cooperative IGS-based FD-NOMA system to maximize its energy efficiency subject to quality-of-service (QoS) requirements. Furthermore, improper constellation diagrams are designed using the predefined optimized IGS coefficients to study the impact of IGS on bit error rate performance. Simulation results demonstrate considerable energy efficiency performance gain of IGS-based FD-NOMA system over its proper Gaussian signaling (PGS)-based FD-NOMA counterpart under residual interference from imperfect self interference cancellation.

Energy Efficiency Maximization for UAV-Assisted Full-Duplex NOMA System: User Clustering and Resource Allocation

In this paper, the problem of energy efficiency maximization of an unmanned-aerial-vehicle (UAV)-assisted full-duplex non-orthogonal-multiple-access (FD-NOMA) system is investigated. In order to reduce the interference among users in the considered system, we first propose a novel and less complex adaptive-geometric distribution (AGD) which adaptively maintain equal cluster size and allocate resource optimally among the users. Later, we formulate an optimization problem of energy efficiency maximization subject to the transmit power budget at the UAV for downlink (DL) users and for each uplink (UL) user and UAV placement. To transform the non-convex problem into convex one, we decouple the original optimization problem into different sub-problems in which the problems of power allocation and UAV placement are alternatively solved using Dinkelbach’s algorithm with successive convex approximation (SCA) and particle swarm optimization (PSO), respectively. Later, the unified solution for optimal power allocation and UAV placement is proposed based on block-coordinate descent (BCD) algorithm. Extensive simulation results validate the superiority of the proposed AGD clustering based proposed algorithm for UAV-assisted FD-NOMA system over the conventional clustering and other orthogonal schemes.

A Wireless Power Transfer Assisted NOMA Transmission Scheme for 5G and Beyond mMTC

In this letter, a wireless power transfer (WPT) assisted full-duplex non-orthogonal multiple access (WPT-NOMA) transmission scheme for massive machine type communications (mMTC) scenario in the 5G and beyond cellular networks has been investigated. The proposed WPT-NOMA allows uplink and downlink users to share energy and radio resources simultaneously, which is crucial in the mMTC scenario to support massive energy-constrained devices with limited radio resources. A resource allocation problem is formulated as an optimization problem to maximize the uplink data rate and minimize the effect of interference from full-duplex transmission. Moreover, to solve the problem, an alternating resource allocation algorithm is proposed. The provided numerical studies demonstrate that WPT-NOMA outperforms benchmark schemes significantly.

Exploiting Incremental Virtual Full Duplex Non-Orthogonal Multiple Access Systems

This paper investigates the throughput performance of an incremental virtual full-duplex non-orthogonal multiple access (I-VFD-NOMA) communication system, where two energy harvesting (EH) enabled near users are willing to forward message for far user using decode-and-forward (DF) protocol. If the direct link between the source and the far user exists, I-VFD-NOMA scheme is used to save the channel resources. If the direct link between the source and the far user does not exist, I-VFD-NOMA can not be used and only VFD-NOMA can be used. With this structure, The analytical expressions of the system throughput considering imperfect successive interference cancellation (I-SIC) and selection combining (SC) are derived when the direct link exists or not. With the aim of maximizing the throughput, the expression for the optimal power splitting factor at near users is also derived when the direct link does not exist. All theoretical results are validated by numerical simulations which demonstrate that the proposed I-VFD-NOMA scheme is superior to existing NOMA systems.

Hardware impairments aware full-duplex non-orthogonal multiple access networks over Nakagami-m channels

Non-orthogonal multiple access (NOMA) and full-duplex (FD) relaying communications are promising candidates for 5G cellular networks. In this paper, by exploiting the impact of hardware impairment, we study FD NOMA communications with a downlink scheme. In a group of two users, we find that the target rates and power allocation strategies are main factors affecting the system performance metric. We derive the closed-form formula of outage probability for two users. As main contribution, numerical results are considered to illustrate the performance of the FD NOMA. We also study the base station (BS) can adjust its transmit signal to noise ratio (SNR) to achieve relevant outage probability in several scenarios.

Impacts of relay and direct links at destinations in full-duplex non-orthogonal multiple access system

In this study, one of effective methods of multiple access, namely non-orthogonal multiple access (NOMA), is investigated. Such NOMA scheme can be worked with signal processing at downlink side. As such, the base station sends mixed signals of two signals to destinations. A near user could be a relay to forward the signal to the distant user by leveraging benefits of full-duplex mode which allows relay to transmit and receive signals in the same time. For simple analysis, the two-user approach and fixed power allocation factors are implemented. We also derive formulas of the outage probability of two users (near-user and far-user) to indicate fairness and emphasize the role of the near user as a relay. This considered NOMA system adopts transmission with Nakagami-m fading channel. As a further metric, throughput is considered under the impacts of key system parameters. The transmit signal-to-noise ratio (SNR) at the base station make influences the performance of two users significantly as observation indicated in our simulation results. These results are confirmed by matching Monte-Carlo with the theoretical simulations.

Impacts of relay and direct links at destinations in full-duplex non-orthogonal multiple access system

Impacts of relay and direct links at destinations in full-duplex non-orthogonal multiple access system

Performance analysis of downlink NOMA relying energy harvesting and full-duplex

This paper considers the implementation of wireless power transfer scheme to non-orthogonal multiple access (NOMA) network at downlink. The single antenna power beacon (PB) provide capability of wireless charge to two NOMA users. In addition, full-duplex (FD) scheme is employed for two users. Outage probabilities related to system performance are evaluated in the scenario of the multi-antenna base station. Improved performance can be achieved since multi-antenna, energy harvesting capability. In particular, expressions of outage performance are derived in this system model to help to forward to serve far NOMA users. As the main advantage, NOMA and full-duplex schemes are two advantages and such a system is deployed to enhance the spectral efficiency. Our simulation results will indicate that main parameters such as a power allocation strategy, energy harvesting time, self-interference factor are the main impacts on considered system. The correct derived expressions are presented by matching Monte-Carlo simulation curves and analytical curves in numerical result section. As our main results, FD NOMA system corresponding the first user and the second user exhibits better than OMA 30% and 25% respectively when SNR at the source is 30 dB.

Performance gap of two users in downlink full-duplex cooperative NOMA

A full-duplex non-orthogonal multiple access (FD-NOMA) systems are expected to play a significant role in fifth generation (5G) networks, addressing spectrum efficiency and massive connections. In this regard, the feasibility of FD communications to improve spectrum utilization is main consideration in term of outage performance. Specifically, we derive exact formulas of outage probability for FD-NOMA, over Nakagami-m fading channels. Extensive analysis revealed that higher quality of channel leads to better performance. We verify expressions throughout Monte-Carlo simulations.

Joint UL/DL Resource Allocation for UAV-Aided Full-Duplex NOMA Communications

This paper proposes an unmanned aerial vehicle (UAV)-aided full-duplex non-orthogonal multiple access (FD-NOMA) method to improve spectrum efficiency. Here, UAV is utilized to partially relay uplink data and achieve channel differentiation. Successive interference cancellation algorithm is used to eliminate the interference from different directions in FD-NOMA systems. Firstly, a joint optimization problem is formulated for the uplink and downlink resource allocation of transceivers and UAV relay. The receiver determination is performed using an access-priority method. Based on the results of the receiver determination, the initial power of ground users (GUs), UAV, and base station is calculated. According to the minimum sum of the uplink transmission power, the Hungarian algorithm is utilized to pair the users. Secondly, the subchannels are assigned to the paired GUs and the UAV by a message-passing algorithm. Finally, the transmission power of the GUs and the UAV is jointly fine-tuned using the proposed access control methods. Simulation results confirm that the proposed method achieves higher performance than state-of-the-art orthogonal frequency division multiple-access method in terms of spectrum efficiency, energy efficiency, and access ratio of the ground users.

Adaptive Power Allocation for Wireless-Powered FD-NOMA System With Cooperation Versus Non-Cooperation

The paper studies a wireless-powered full-duplex non-orthogonal multiple access (NOMA) system with one base station and two groups of near and far users, where the near users can be regarded as the self-energy recycling relays to assist the far users. In particular, the locations of the near and far users are modeled as the uniformly distributed and homogeneous Poisson Point Process respectively. From the beneficial perspective of the near users, we propose a novel power allocation scheme, which can utilize the partial channel state information to switch the transmission mode dynamically between cooperative NOMA and non-cooperative NOMA. Further, since the users’ locations have a significant influence on our proposed power allocation scheme, three different user selection strategies namely random near user and random far user (RNRF), optimal near user and nearest far user (ONNF), and optimal near user and farthest far user (ONFF) are investigated to carry out NOMA pairing. Firstly, the RNRF allows all of users to communicate with the base station by a fair opportunity compared to the others strategies, and then a two-stage user selection method is proposed by considering the actual states of near users to determine an optimal near user who can maximize the outage performance of far user for ONNF and ONFF strategies. In addition, outage probabilities, diversity orders, and system throughputs are derived to characterize the performance of three strategies. Finally, numerical results are shown to verify that not only our proposed power allocation scheme can improve the quality of service of near users but also user selection strategies can fully exploit multi-user diversity in comparison to the existing work.

On the performance of physical layer security in virtual full-duplex non-orthogonal multiple access system

This paper investigates physical layer security analysis of cooperative non-orthogonal multiple access (NOMA) communication system. A virtual full-duplex (VFD) relaying scheme with an untrusted amplify-and-forward (AF) half-duplex (HD) relay and a trusted decode-and-forward (DF) HD relay is used in this system to improve the spectral efficiency. In order to prevent the untrusted relay from eavesdropping, a simple and practical cooperative jamming scheme is designed to confuse the untrusted relay. The exact expressions of effective secrecy throughput (EST) for NOMA users and approximate expression of EST for non-NOMA user are derived. All theoretical results are validated by numerical simulations which demonstrate that the proposed VFD-NOMA scheme is superior to existing HD-NOMA scheme in cooperative system and jamming plays an important role for obtaining acceptable EST. In addition, simulation results shows that the best secrecy performance highly depends on the system parameters such as transmit powers and jamming signal power.

Hardware Impairments Aware Full-Duplex NOMA Networks Over Rician Fading Channels

A cooperative full duplex (FD) nonorthogonal multiple access (NOMA) scheme over Rician fading channels is considered. The practical, imperfect successive interference cancellation and residual hardware impairments at transceivers are taken into account. To evaluate the performance of the considered system, the analytical approximate expressions for the outage probability and the ergodic rate of the considered system are derived, and the asymptotic performance is also explored. Simulation results manifest that the FD cooperative NOMA can improve the ergodic sum rate of the system compared to the half-duplex mode.

Secure Non-Orthogonal Multiple Access: An Interference Engineering Perspective

Non-orthogonal multiple access (NOMA) is an efficient approach that can improve spectrum utilization and support massive connectivity for next-generation wireless networks. However, over a wireless channel, the superimposed NOMA signals are highly susceptible to eavesdropping, potentially leading to severe leakage of confidential information. In this article, we unleash the potential of network interference and exploit it constructively to enhance physi-cal-layer security in NOMA networks. In particular, three different types of network interference, including artificial noise, specifically-designed jamming signals, and inter-user interference, are well engineered to intentionally reduce information leakage while mitigating the effect on signal reception quality of legitimate users, thereby significantly enhancing the transmission security of NOMA. Furthermore, we propose interference engineering strategies for more advanced full-duplex NOMA, intelligent reflecting surface NOMA, cognitive radio NOMA, and multi-cell NOMA networks, and discuss several open research problems and challenges, which could inspire innovative interference engineering designs for secure NOMA communications.

Full-Duplex Nonorthogonal Multiple Access With Layers-Based Optimized Mobile Relays Subsets Algorithm in B5G/6G Ubiquitous Networks

In view of noteworthy communications performance improvements for future B5G/6G ubiquitous networks (such as cognitive Internet of Things (IoT) network, UAV communications, air-space-ground integration network, and so on), cooperative communications (CCs) diversity with relays selection algorithms has been extensively studied to significantly improve communications quality. In light of unsolved millennium issue in CC—nondeterministic polynomial (NP) and NP-hard problems have not been solved efficiently for relays subsets selection, in this article, theorems of relays subsets with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> -layers power allocation standard have been further put forward to explore better performance in B5G/6G networks. We propose unified layers-based optimized mobile relays subsets algorithms for full-duplex (FD) nonorthogonal multiple access (NOMA) to greatly improve transmission rates. After taking into account fundamental properties of relays, such as mobile relays nodes state, relays locations, fading characteristics, and so on, optimized FD-NOMA algorithm based on these relays features has been presented to improve transmission rates, and a related series of relays subsets theorems has been derived and proved, then minimum upper bound of maximum transmission rates is estimated to reveal two-way balanced optimal transmission conclusion for FD-NOMA. Furthermore, simulation results show that proposed algorithm has 1–3 dB advantage than other relays subset algorithms for signal to interference and noise ratio (SINR), and it can more efficiently transform NP-hard problem to P problem for relays selection. Importantly, under revealed two-way balanced optimal transmission phenomenon for FD-NOMA, the proposed scheme with FD-NOMA has more than two times minimum device-to-device (D2D) transmission rates higher than other classical relays selection algorithms.