Full-duplex Networks Research Articles

Uplink–Downlink Cochannel Interference Cancellation in RIS-Aided Full-Duplex Networks

Uplink–Downlink Cochannel Interference Cancellation in RIS-Aided Full-Duplex Networks

Contention With Collision Detection in Wireless Full-Duplex Networks

Contention With Collision Detection in Wireless Full-Duplex Networks

Recent advancement of RB noise alleviation techniques in different communication networks and its lacunae: a review

Abstract Telecommunication networks are forced to be advanced day by day for high data rate transportation over long-reach to fulfil the ever-increasing demand of the subscribers. Different used schemes, modulation techniques are smart enough to support high data rate transmission over long distance but some impairment like Rayleigh backscattering (RB) brings a limitation on data rate or transmission distance. RB noise effect arises and affects the system performance when more than one signal of similar wavelengths are transmitted through a same feeder fiber in full-duplex networks and different researchers have already proposed various schemes to eliminate RB noise effect in different transport networks. The present paper surveys and analyses the techniques which proposed in last 15 years for mitigation of RB noise in communication systems. The origin of RB and the impact of it in different communication systems are also explained. All the proposed networks are aimed to support next generation communication systems by providing high data rate (up to 160 Gbps downstream and 20 Gbps upstream) over long reach (up to 115 km single mode fiber link) with lesser RB noise effect but exact quantification of RB noise mitigation is not reported till now which could be a future scope for the new researchers.

Spectral-Energy Efficiency and Power Allocation in Full-Duplex Networks: The Effects of Hardware Impairment and Nakagami-$m$ Fading Channels

Full-duplex (FD) systems have emerged as game-changers for the future of wireless communication thanks to their ability to increase spectral efficiency (SE) and energy efficiency (EE). In this article, we study the effect of hardware impairments (HWIs) on Multiple-input Multiple-output (MIMO) FD systems. We derived closed-form expressions for the lower bounds of the average UL and DL achievable rates. We formulate different power allocation optimization problems to maximize the average FD SE and EE, while satisfying the quality of service (QoS) and power budget constraints. Moreover, we consider the max-min objective functions to assure fairness between users. These problems are solved using different optimization techniques, including the Dinkelbach approach, transformation, and the Karush–Kuhn–Tucker (KKT) conditions. We also refine the SE algorithm and present a simpler solution. Finally, we assume that all fading channels follow Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$m$</tex-math></inline-formula> distributions, where other scenarios can be considered special cases. Extensive simulations were performed to validate the presented analysis.

Partial and Full Relay Selection Algorithms for AF Multi-Relay Full-Duplex Networks With Self-Energy Recycling in Non-Identically Distributed Fading Channels

Full-duplex communication offers enhanced spectral efficiency for relay deployment, but suffers from the inherent self-interference from the strong transmit signal coupling to the sensitive receive chain. In this article, we propose a self-energy recycling (S-ER) protocol for full-duplex multi-relay networks, in which the energy from self-interference is harvested back at the relay for future use. Furthermore, two amplify-and-forward (AF) relay selection algorithms, namely, partial relay selection (PRS) and full relay selection (FRS) are introduced to enhance the reliability of the proposed systems. For PRS, the best relay is selected based on just the knowledge of the channels from the source to all relays, while in FRS, the best relay is selected based on the end-to-end signal-to-noise ratio, which requires knowledge of all source-relay and relay-destination links. We provide a thorough analysis on the outage performance and the spectrum efficiency of the proposed algorithms in both cases: all channel gains are independently but non-identically distributed (i.n.d.) (case 1) or independently, identically distributed (i.i.d.) (case 2) Rayleigh random variables. It is shown that SER and FRS can significantly enhance the performance of FD networks and avoid the outage floor when the number of relays increases, while the outage probability (OP) in PRS case reaches an outage floor. In addition, the end-to-end signal-to-noise ratio in both cases can be minimized if an optimal power-splitting factor is selected. All analytical results are verified by Monte Carlo simulation.

Robust Resource Allocation for Lightweight Secure Transmission in Multicarrier NOMA-Assisted Full Duplex IoT Networks

In this article, with the aim to enhance the secure transmission and improve the utilization of spectrum resources in Internet of Things (IoT), a multicarrier nonorthogonal multiple access (MC-NOMA)-assisted full duplex (FD) network is investigated, in which nonorthogonal multiple access (NOMA) is implemented in both uplink and downlink transmissions. The lightweight and low-power physical layer security (PLS) technology is employed to protect the information from eavesdropping. Taking the imperfect channel state information (CSI) into account, we formulate a problem to optimize the beamforming vector, artificial noise (AN), transmit power, and subcarrier assignment policy aiming to maximize the worst case sum secrecy rate under the Quality of Service (QoS) and power consumption constraints. Since the formulated problem is nonconvex and difficult to be solved, we decompose it into two joint optimization subproblems. The first is resource allocation with given subcarrier assignment, which is solved by using the block coordinate descent (BCD) approach. The second is subcarrier assignment solved by the matching theory. Our simulation shows that the proposed scheme is robust against the CSI imperfectness of the eavesdropping and self-interference channels, while providing significant sum secrecy rate improvement compared with the orthogonal multiple access (OMA), half duplex (HD) systems, and other benchmark schemes.

Splitting Energy of Transmit Power Serving Grouping Users in Full-Duplex Networks under Imperfect Hardware

In this paper, we consider a wireless system providing power allocation fairness for grouping users by conducting a non-orthogonal multiple access (NOMA). In particular, a rigorous analysis is performed to evaluate performance of destination in a downlink of wireless system. With advances of NOMA, the user grouping scheme allows users to be shared the same frequency/power domain, and hence, fairness is guaranteed. In this regard, we focus on evaluation of the performance of a cell-center user and a cell-edge user in dedicated group. To enable forwarding function at cell-center user, we require the assistance of a full-duplex– (FD–) based relay to serve the cell-edge user. These users are assigned a fixed power allocation scheme. To characterize system performance, the closed-form expressions of the outage probability are computed for two users. To generalize channels in such system, Nakagami-m fading channels could be adopted to achieve complete theoretical analysis. Furthermore, we provide some comparisons of such FD NOMA under the impact of hardware impairment. We find that a significant improvement of outage probability can be achieved when the signal-to-noise ratio (SNR) at the source is high. Numerical results illustrate that both the analytical outage probability of the central user and the cell-edge user match the simulation results.

The Optimal Power Allocation for Sum Rate and Energy Efficiency of Full-Duplex Two-Way Communication Network.

Full-duplex (FD) transmission holds a great potential of improving the sum data rate of wireless communication systems. However, the self-interference introduced by the full-duplex transmitter brings a big challenge to enhance the energy efficiency. This paper investigates the power allocation problem in a full-duplex two-way (FDTW) communication network over an OFDM channel, aiming at improving the sum data rate and energy efficiency. We first characterize the sum rate and energy efficiency achieved in a single-carrier FDTW system. The optimal transmit power that achieves the maximal sum data rate is presented. The energy efficiency maximization problem is solved by using fractional programming. Then we further formulate sum rate and energy efficiency maximization problem in a multi-subcarrier FDTW system. In particular, the sub-optimal transmit power allocation which achieves a decent sum rate improvement is found by using a proposed iterative algorithm. By combining the iterative algorithm and fractional programming, we further maximize the energy efficiency of the multi-subcarrier system. With our proposed algorithm, we can easily obtain an optimal transmit power that approximates the global optimal solution. Simulation results show that using the obtained optimal transmit power allocation algorithm can significantly improve the sum rate and energy efficiency in both single-carrier and multi-subcarrier systems.

A SIC-Based BS Coordination Scheme for Full Duplex Cellular Networks

Full Duplex (FD) in cellular networks is expected to increase the cell spectral efficiency. However, while the downlink (DL) spectral efficiency (SE) increases with FD, the uplink (UL) SE decreases because of the Base Station to Base Station (BS) interference. In this paper, assuming a three-node model, we propose a method based on Successive Interference Cancellation (SIC) to reduce the BS-to-BS interference present in FD cellular networks. The approach consists in coordinating BSs to enable the decoding and the suppression of undesired signals that impair uplink transmissions. We analyze both distributed and Centralized Radio Access Networks (CRAN) architectures. Stochastic geometry is used to derive the coverage probability and mean data rate of the proposed scheme. In the distributed scenario, the FD UL average data rate is increased by 25% with our solution compared to a classical FD network, while our FD scheme still outperforms Half-Duplex (HD) on the DL. In the centralized scenario, our solution outperforms HD by 10% and classical FD by 78% on the UL, while preserving classical FD gains on the DL.

Physical Layer Secrecy by Power Splitting and Jamming in Cooperative Multiple Relay Based on Energy Harvesting in Full-Duplex Network

In this article, we investigated the secrecy performance of a three-hop relay network system with Power Splitting (PS) and Energy Harvesting (EH). In the presence of one eavesdropper, a signal is transferred from source to destination with the help of a relay. The source signal transmits in full-duplex (FD) mood, jamming the relay transfer signals to the destination. The relay and source employ Time Switching (TS) and Energy Harvesting (EH) techniques to obtain the power from the power beacon. In this study, we compared the Secrecy Rate of two Cooperative Schemes, Amplify and Forward (AF) and Decode and Forward (DF), for both designed systems with the established EH and PS system. The Secrecy Rate was improved by 50.5% in the AF scheme and by 44.2% in the DF scheme between the relay and eavesdropper at 40 m apart for the proposed system in EH and PS. This simulation was performed using the Monto Carlo method in MATLAB.

Rate maximization in full‐duplex systems: Gains and complexity of employing adaptive power allocation in downlink and/or uplink

AbstractThe next generations of mobile communications should deal with a set of new use cases, leading to a higher demand for spectral efficiency. Full‐duplex (FD) arises as a promising technology since it has the potential to double the system capacity without additional spectrum. However, FD networks are hindered by self‐interference (SI) and co‐channel interference caused by the reuse of frequency resources. Therefore, radio resource allocation (RRA) in FD networks by means of user pairing, frequency assignment, and power allocation are of utmost importance in order to improve spectral/energy efficiency and ensure quality of service (QoS). Although previous works investigated RRA to improve spectral efficiency, the fundamental question of where adaptive power allocation should be employed in the uplink and/or downlink of FD networks in a cost‐effective way remains unanswered. This article addresses this question in the context of total data rate maximization with QoS constraints where we propose four optimization problems using different power allocation strategies. The branch and bound method is employed to optimally solve the four formulated problems, which were used as upper bound solutions for benchmarking purposes. Moreover, we propose a low computational complexity solution able to adaptively switch the power allocation strategy depending on the scenario. Detailed system‐level simulations indicate that the best node to employ adaptive power allocation (mobile terminal or base station) depends on the cell radius and SI level. Also, our results show that, compared to existing solutions, the proposed low‐complexity is a great and intelligent strategy in terms of system performance and computational complexity considering both perfect and imperfect channel state information.

Physical layer security in cognitive NOMA sensor networks with full-duplex technique

This article studies the physical layer security in a downlink full-duplex cognitive non-orthogonal multiple access sensor networks (FD-C-NOMA). Compared with the existing works, this article proposes a FD-C-NOMA transmission scheme with a primary user (PU) and secondary user (SU) sensor nodes in the presence of an eavesdropper. The zero-forcing beamforming design problems of FD operation are investigated subject to the practical secrecy rate and the quality of services of PU. To characterize the security reliability trade-off of the FD-C-NOMA scheme, we first derive the closed-form expressions of connection outage probability (COP), the secrecy outage probability (SOP), and effective secrecy throughput (EST) of each SU in the NOMA networks. Then the impacts of the system parameters on the COP, SOP, and EST are investigated to evaluate the security and reliability in the FD-C-NOMA networks. Furthermore, in order to further verify the security and reliability of our considered network, an OMA scheme of FD operation is provided in the simulation for the purpose of comparison. Results demonstrate that the NOMA-based cognitive sensor networks of FD operation outperforms the OMA system in terms of EST. Finally, simulations are performed to validate the accuracy of our analysis results of the proposed scheme.

A Novel MAC Protocol with Fusion Center and Adaptive Full-Duplex Communication for Cognitive Radio Networks

Cognitive radio network is an intelligent and adaptive communication technology used to effectively utilize the radio spectrum to provide better communication. It enables the secondary (unlicensed) users to communicate over vacant channels without disrupting the communication of the primary (licensed) users. This paper proposes a novel contention-free MAC protocol for full-duplex and half-duplex cognitive radio networks. A novel concept of a fusion center-based channel allocation scheme is proposed to provide better channel allocation and reduced energy consumption. The proposed technique is compared with the existing techniques in terms of the average number of channels being sensed by each user, average wait time, collisions, throughput, and average energy consumption. The number of collisions increases as the maximum allotted time of communication increases in existing approaches. The experiment is performed with 20, 40, 60, and 80 s. The existing approaches show for 20 s, the number of collisions is 65, 61, 68, and 62; for 40 s, the number of collisions is 93, 96, 95, and 92; for 60 s, the number of collisions is 122, 126, 133, and 130; for 80 s, the number of collisions is 176, 170, 173, and 175. The proposed method approaches the number of collisions will become zero as the maximum allotted time of communication increases. The experimental results show that the proposed approach performs better than existing approaches. Moreover, it can be observed that the average waiting time of secondary users when a collision occurs is reduced with the application of a fusion center-based channel allocation scheme.

Fractional Frequency Reuse in Random Hybrid FD/HD Small Cell Networks With Fractional Power Control

Small cells are regarded as a promising solution for improving the coverage and spectral efficiency of the fifth generation (5G) cellular networks. Small cell networks utilize low transmission power levels and thus, are appropriate for deploying full-duplex (FD) technology. In this paper, a hybrid full/half duplex (FD/HD) small cell network exploiting fractional frequency reuse (FFR) and fractional power control (FPC) for interference mitigation is considered. Theoretical expressions for the coverage probability and the average sum-rate in uplink and downlink directions are derived for systems that make use of conventional frequency reuse, hard FFR, and soft FFR. The impact of various system parameters, such as power control parameter, small base station (SBS) density, and self-interference cancellation (SIC) parameters on system performance are investigated. The numerical experiments show that SBSs tend to operate in FD mode for large values of SBS density and SIC level. Also, interestingly, the optimal sum-rate is achieved when all SBSs operate either in FD or in HD mode. Finally, it is observed that exploiting FFR techniques in FD networks making use of FPC, significantly improves downlink coverage probability.

Research on Key Technology of Full Duplex Cognitive Radio Network

In traditional half duplex cognitive radio networks, secondary users can only sense the spectrum or transmit at a given time. This kind of half duplex network limits the throughput of users, because the user unit can’t transmit data in spectrum sensing. However, with the development of self-interference suppression (SIS) technology, full duplex cognitive radio network allows spectrum sensing and data transmission on a given channel at the same time. Compared with traditional half duplex network, full duplex network improves throughput and reduces conflicts. In order to explore the future development direction of spectrum sensing technology, in the context of full duplex cognitive radio, a comprehensive study of radio network is carried out, including key technologies, current challenges and future research directions.

Optimized resource allocation in full-duplex cloud radio access network using firefly algorithm

ABSTRACT The main objective of the study is to allocate the resources in a Full-duplex cloud radio access network. Also, the use of C-RAN suppresses the self-interference because of the distributed behaviour of Remote Radio Head in C-RAN. Full-duplex communication system allows data to be transmitted and received between stations simultaneously. It has double the spectral efficiency of half-duplex communication system. The work aims to find the optimal value of the power that is allocated to the remote radio head when data rate is maximum. For the optimization, Firefly Algorithm is employed. It is an optimization algorithm that works similar to the firefly’s attraction towards flashing light. The brighter firefly attracts the less bright one to move towards them. It is an iterative process and eventually, the population of firefly converges to brightest one. When maximum inverse data rate is achieved, the corresponding power value is noted and they are employed for the distribution among the single antenna and multiple antenna remote radio heads. In order to find the best cost value, power constraints are applied to it. Finally, the proposed work is compared with generalized benders decomposition (GBD)-based resource allocation (GRA) algorithm by plotting graphs using MATLAB.

QoS-Guaranteed Resource Allocation for Full-Duplex Networks With M2M/H2H Co-Existence Under Imperfect CSI

To enhance spectrum efficiency for the future Internet-of-Things, in this paper, we investigate the joint subcarrier and power allocation problem for a full-duplex network with machine-to-machine nodes and cellular nodes. We aim to maximize the network spectral efficiency while achieving individual quality-of-service (QoS) requirements, considering imperfect and partial channel state information. The spectral efficiency maximization problem is formulated as a mixed-integer nonlinear programming problem and proved to be NP-hard. To make it more tractable, we first solve the coupling between subcarrier assignment and power allocation variables by replacing the product of two variables with one auxiliary variable. We then relax the binary subcarrier assignment variables to integer variables and introduce penalty terms to penalize the objective function. Majorization minimization method is adopted to further handle the coupling between uplink and downlink due to full-duplex transmission. We prove that the proposed joint resource allocation scheme converges to local optimal solution. Simulation results demonstrate the impact of channel estimation error on spectral efficiency and the superiority of the proposed algorithm.

FD MAC Protocol Design for Co-Existing WLANs in 5G Cellular Networks

Abstract In this paper, we design full-duplex (FD) medium access control (MAC) protocol for co-existing wireless local area networks (WLANs) in 5G cellular networks (WCFD-MAC). Our design considers some significant features of 5G networks, exceptionally, beamforming and FD capabilities at both, the base station and user equipment. FD communications may generate interferences, namely self-interference (SI) in bidirectional FD (BFD) and inter-user interferences in three-node FD (TNFD). Several efforts have been performed to mitigate the SI in BFD communications. However, the inter-user interferences in TNFD are still considered as a major drawback in FD networks. These interferences must be mitigated by an efficient MAC protocol design. WCFD-MAC protocol allows two neighboring users to simultaneously participate in TNFD communication without interfering with each other by using directional transmission and a three-node angle condition (TAC). Directional transmission combined with TAC increases system throughput. WCFD-MAC protocol allows a new half-duplex (HD) communication scheme referred to as three-node HD (TNHD). This scheme may occur when bidirectional FD (BFD) and TNFD communications cannot occur. TNHD scheme includes device-to-device (D2D) communication and allows energy efficiency, which is one of the keys requirements of 5G wireless networks. Simulations results show that WCFD-MAC protocol achieves higher throughput than existing works in the literature.

When Buffer-Aided Relaying Meets Full Duplex and NOMA

Full duplex (FD) systems are able to transmit and receive signals over the same frequency band simultaneously with the potential of even doubling the spectral efficiency in comparison with traditional half duplex (HD) systems. When combined with relaying, FD systems are expected to dramatically increase the throughput of future wireless networks. However, the degrading effect of self-interference (SI) due to the simultaneous transmission and reception at the relay threatens their efficient rollout in real-world topologies. At the same time, non-orthogonal multiple access (NOMA) can further increase the spectral efficiency of the network. In this article, we present how buffering at the relays can be integrated with FD and NOMA in order to improve the performance of relay networks. More specifically, the key points for the successful integration of buffer-aided relays with spatial sharing paradigms are presented, and details on buffer-state-information-based relay selection and its fully distributed implementation are discussed. Furthermore, a mathematical framework for the analysis of FD and HD buffer-aided relay networks is rigorously discussed. Performance evaluation shows the importance of data buffering toward mitigating SI and improving the sum-rate of the network. Finally, the goal of this work is both to summarize the current state of the art and, by calling attention to open problems, to spark interest toward targeting these and related problems in relay networks.

Multiple Access Control in a Centralized Full-Duplex Cognitive Machine Type Network with RF Energy Harvesting

Machine type communication connecting machines in the Internet of Things (IoT) brings massive traffic and rapidly increases the demand for radio spectrum in wireless networks. To transmit the traffic in limited spectra, a time division multiple access (TDMA) based interface with a reservation scheme, which is spectrum-efficient, energy-efficient, and deployment-economical, was proposed in cognitive radio based machine type communication. Since radio frequency (RF) energy harvesting is a way to charge stand-alone or low-power machines in IoT and full-duplex communication potentially doubles spectral efficiency, this paper proposes a multiple access control that incorporates RF energy harvesting and full-duplex communication into the TDMA based interface with a reservation scheme. The proposed multiple access control elaborately uses the full-duplex functionality with a mechanism of detecting primary users to appropriately turn on/off RF charging such that the trade-off between the interference of primary users and RF charging is balanced. Extensive simulation results show that the proposed multiple access control produces high system throughput while the interference of primary users is kept at a low level.