Search

ABSTRACT In this paper, a passive reflective intelligent surface (RIS) assisted bidirectional full‐duplex (FD) wireless system in a realistic Nakagami‐m$$ m $$ fading with N$$ N $$ reflective elements and two source nodes is proposed. The source nodes are equipped with dual antennas for FD mode transmission and reception. The primary cause of degradation in the performance of the FD system is self‐interference, which can be reduced by increasing the number of reflective elements on the meta‐surface. Analytical expressions have been derived for the proposed RIS‐aided bidirectional FD wireless systems in terms of outage probability and bit error rate (BER). Numerical results show that doubling the number of reflecting elements considerably improves the outage performance of the proposed system in terms of signal‐to‐noise ratio (SNR) compared with RIS‐assisted half‐duplex (HD) mode. Additionally, different modulation schemes have been employed to evaluate the BER performance of the proposed system. The accuracy of analytical expressions is validated by matching Monte Carlo with analytical simulations. [ABSTRACT FROM AUTHOR]

This study explores a dual-user full-duplex cooperative non-orthogonal multiple access (FD-CNOMA) network, presenting closed-form expressions for the outage probability (OP) and effective capacity (EC) of both users. The analytical results indicate that an increased signal-to-noise ratio (SNR) corresponds to a reduced OP and heightened EC, signifying enhanced communication quality. We analyze the OP and EC under two cases: R1=2R2 and R1=R2. Our analytical expressions reveal that both θ and ρ significantly impact the effective capacities. To validate these analytical findings, Monte Carlo simulations are performed, demonstrating alignment between theoretical insights and practical outcomes. The results underscore the critical role of SNR in influencing network performance, providing valuable insights into optimizing communication quality in FD-CNOMA systems. [ABSTRACT FROM AUTHOR]

In this paper, we consider a full-duplex decode-and-forward(DF) relaying with multiple antennas for a covert communication system. We first derive the covert communication constraint that achieves the successful covert communication for the covert communication system with full-duplex DF relay. Then, we design the relay beamforming vector in order to maximize the covert rate of the destination subject to the covertness requirement of the system. Specifically, we first design the relay beamforming vector that maximizes the covert rate of the destination and relay beamforming vector that minimizes the covertness requirement of the system, independently. Then, we finally design the relay beamforming vector as a linear combination of the designed two type of beamforming vectors to achieve both covert rate maximization and covertness requirement. In the simulation results, we show that the proposed full-duplex DF relay beamforming technique improve the covert rate comparing to the existing schemes. [ABSTRACT FROM AUTHOR]

In response to the limitations of traditional reconfigurable intelligent surfaces (RIS) in UAV-assisted secure communications, such as insufficient flexibility and inadequate system security, as well as the challenges of low spectral efficiency and poor communication efficiency faced by current half-duplex UAV communication systems, a dual-machine cooperative solution involving aerial reconfigurable intelligent surfaces (ARIS) and full-duplex UAV was proposed, aiming at enhancing communication security and efficiency against ground eavesdroppers. An optimization problem was designed to maximize the minimum average achievable security rate by jointly optimizing user communication scheduling, transmission power, the interference power sent by UAV, their flight trajectories, and the phase shifts and trajectories of ARIS. An iterative algorithm based on alternating optimization (AO), semi-definite relaxation (SDR) techniques, and successive convex approximation (SCA) was proposed to obtain high-quality suboptimal solutions. Simulation results demonstrate the effectiveness of the ARIS and full-duplex UAV combination in enhancing communication quality and security performance, showcasing its superiority in complex security communication environments.

To address the issues of frequency switching differences between communication and sensing systems in traditional integrated sensing and communication (ISAC) scenarios, as well as the susceptibility of communication to obstruction by obstacles, the integration of full-duplex (FD) technology and intelligent reflecting surface (IRS) into the ISAC system was studied. The design of FD beamforming assisted by IRS in the ISAC scenario was investigated. An optimization problem for maximizing the user rates of uplink and downlink beamforming was formulated, considering constraints on IRS phase shift, base station receiving beamforming, the maximum transmission power of the base station, the maximum transmission power of uplink users, and the radar sensing threshold. The original non-convex problem was solved by being transformed into a convex optimization problem through the use of alternating optimization, continuous convex approximation, semi-definite relaxation, variable substitution, and semi-definite programming. Simulation results show that the proposed scheme resulted in an 89.02% enhancement under the communication performance indicators considered compared to the corresponding half-duplex scheme and a 70.15% improvement over the random IRS scheme.

With small size, low cost and high mobility, unmanned aerial vehicles (UAVs) are playing an increasingly important role in all areas of modern society. In this paper, a full-duplex (FD) UAV equipped with a large antenna array is investigated as a relay base station (BS) to provide services to multiple ground users (GUs) using millimeter-wave (mmWave). Specifically, we propose a joint optimization problem based on user scheduling, UAV flight trajectory, beamforming and UAV transmit power to maximize the average transmission rate of the overall system. As the problem described is highly coupled and non-convex, making it difficult to solve, we propose an iterative algorithm based on the block coordinate descent (BCD) technique and the successive convex approximation (SCA) techniques to obtain an approximate optimal solution. Simulation results show that the proposed algorithm is able to converge with a small number of iterations and can significantly improve the system throughput. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunications Science is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Telecommunications Science is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Designing circulator as an antenna interface device becomes a daunting task, particularly active‐quasi circulator. This article focuses on demonstrating the basic operation principle, design methods, technical parameters, and performance metrics of active quasi‐circulator. In addition, the study provides an analogy of the circuits and structures proposed by the researchers to enhance certain performance metrics. Active signal cancellation and passive signal cancellation are identified as the major design approaches. Tunable, wideband, and wideband‐tunable are the major types of circulators found in existing literature. Moreover, this article provides a performance comparison of the active‐quasi circulators available in existing literature. Several active quasi‐circulators were able to operate in high frequencies such as 60 GHz with acceptable isolation levels. On the other hand, several designs have over 30 dB isolation, which is a highly desired parameter. At last, the future design challenges associated with active‐quasi circulators have been discussed to provide insight into future research. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we improve networks’ spectral efficiency (SE), extend networks’ lifetime, and maximize networks’ energy efficiency (EE) of two-way full-duplex (FD) relay networks. Firstly, to improve networks’ SE and to extend networks’ lifetime simultaneously, we design a two-way FD relay transmission strategy with simultaneous wireless information and power transfer and direct links (DLs). The designed transmission strategy can complete a bidirectional communication in only one time slot with the exists of DLs and the energy-constrained relay node. With the designed transmission strategy, we further give the characteristics of relay amplification factor, the analysis of the designed transmission strategy, and the EE analysis of traditional half-duplex two-way amplify-and-forward relaying. Secondly, to maximize networks’ EE, we present both the EE maximization problems and analyses of the designed transmission strategy with equal power allocation and optimal power allocation. To solve the EE maximization problems, we further propose the alternating optimal algorithm and give complexity analysis of the algorithm. Simulations show that our designed transmission strategy can improve the SE and EE of the networks.

This paper examined uplink and downlink di-state (primary and secondary) situations to build the theoretical and practical realization of a bidirectional cooperative wireless cellular network. In the primary scenario, full-duplex (FD) base stations support two sets of half-duplex (HD) users, where the transmitter (uplink) and receiver (downlink) respectively. Each uplink transmitted signal is rotated in a variant phase through a set of scalars known to the base stations before transmission. The signal from the transmitter ensures the reconfigurable receiver antennas at the base stations can configure the received signal as decoded signals. The proposed work exposed strong self and inter-user interference from the transmitter during demonstrating FD wireless communication mode that destroyed network functionality at the base stations. The occurred self-interference signals from the transmitter are neutralized using precoding and beam-forming technique. During the secondary scenario, decoded base station signals are independently encoded and transmitted to the downlink users. Base stations aid the inter-user interference management by precoding the uplink transmission data and forwarding it to the downlink users. Consequently, the inter-user interference signals are aligned using the span interference alignment technique. A proposed cooperative additional receiver (listener U1) can decode the desired signals and helps in recovering and reconstructing the interference signals. This proposed work completely characterized and evaluated the degree of freedom (DoF) for unknown channel state information at the transmitter (CSIT); whereas achievable lower and upper bound DoF are demonstrated for the partial CSIT. At last, the analytical and simulation results reveal the sum of DoF improvement for unknown and partial CSIT.

In this paper, a novel data transmission scheme, interference perceptual multi-modulation (IP-MM), is proposed for full-duplex (FD) systems. In order to unlink the conventional uplink (UL) data transmission using a single modulation and coding scheme (MCS) over the entire assigned UL bandwidth, IP-MM enables the transmission of UL data channels based on multiple MCS levels, where a different MCS level is applied to each subband of UL transmission. In IP-MM, a deep convolutional neural network is used for MCS-level prediction for each UL subband by estimating the potential residual self-interference (SI) according to the downlink (DL) resource allocation pattern. In addition, a subband-based UL transmission procedure is introduced from a specification point of view to enable IP-MM-based UL transmission. The benefits of IP-MM are verified using simulations, and it is observed that IP-MM achieves approximately 20 % throughput gain compared to the conventional UL transmission scheme. [ABSTRACT FROM AUTHOR]

Assuming incomplete knowledge of the channel state information (CSI), we investigate two scenarios involving millimeter wave (mmWave) relaying to support outdoor-to-indoor communications. We proceed to derive the average signal-to-noise ratio (SNR) expressions for two relaying scenarios and quantify the asymptotic SNR. The performance of the two relaying scenarios is evaluated using the outage probability—for which we have derived closed-form equations—the end-to-end channel capacity, and the energy efficiency. The obtained results are compared with those derived assuming complete knowledge of the CSI. The effect of the imperfect CSI is therefore assessed in relation to the reference of perfect CSI. In these scenarios, an outside base station (BS) in an urban cellular network serves several indoor users. In the context of a two-hop full-duplex (FD) relaying scheme, we initially suggest a method in which the base station (BS) utilizes zero-forcing (ZF) precoding, and we take into account the overall channel response. Furthermore, we make the assumption that the base station (BS) engages in precoding only depending on the response of the channel in the first hop; in this second design, the relay precodes (using the response of the second-hop channel), amplifies, and sends the signals. Both techniques utilize massive multiple-input–multiple-output (mMIMO) arrays to permit transmission. We also present Monte Carlo simulation results to assess the accuracy of our analytical results. Finally, the two systems are compared in terms of channel estimation and precoding complexity, the number of antennas, as well as the number of users. Practical deployment recommendations are formulated at the end of this work. [ABSTRACT FROM AUTHOR]

In this paper, we improve networks' spectral efficiency (SE), extend networks' lifetime, and maximize networks' energy efficiency (EE) of two-way full-duplex (FD) relay networks. Firstly, to improve networks' SE and to extend networks' lifetime simultaneously, we design a two-way FD relay transmission strategy with simultaneous wireless information and power transfer and direct links (DLs). The designed transmission strategy can complete a bidirectional communication in only one time slot with the exists of DLs and the energy-constrained relay node. With the designed transmission strategy, we further give the characteristics of relay amplification factor, the analysis of the designed transmission strategy, and the EE analysis of traditional half-duplex two-way amplify-and-forward relaying. Secondly, to maximize networks' EE, we present both the EE maximization problems and analyses of the designed transmission strategy with equal power allocation and optimal power allocation. To solve the EE maximization problems, we further propose the alternating optimal algorithm and give complexity analysis of the algorithm. Simulations show that our designed transmission strategy can improve the SE and EE of the networks. [ABSTRACT FROM AUTHOR]

This paper investigates a novel full-duplex (FD) simultaneous wireless information and power transfer (SWIPT) based cooperative non-orthogonal multiple access (FDS-NOMA) system, where far distant NOMA IoT users are helped by the NOMA strong user with the capability of energy harvesting (EH) and FD communications. The downlink (DL-NOMA) principle is used to transmit the superimposed signals from source i.e a base station (BS) to an energy-limited FD relay where relay harvests energy from the transmit power of the BS. The relay after detecting the superimposed signals using successive interference cancellation (SIC), retransmits the decoded signals using superposition coding to the IoT users. We derive the analytical expressions of the outage probability and ergodic rates experienced by the NOMA strong user as well as NOMA IoT users. The results shows that proposed cooperative NOMA scheme can be used to serve IoT users using EH relay. Extensive simulations are performed to verify the accuracy of the derived approximate closed-from expressions. [ABSTRACT FROM AUTHOR]

This paper examined uplink and downlink di-state (primary and secondary) situations to build the theoretical and practical realization of a bidirectional cooperative wireless cellular network. In the primary scenario, full-duplex (FD) base stations support two sets of half-duplex (HD) users, where the transmitter (uplink) and receiver (downlink) respectively. Each uplink transmitted signal is rotated in a variant phase through a set of scalars known to the base stations before transmission. The signal from the transmitter ensures the reconfigurable receiver antennas at the base stations can configure the received signal as decoded signals. The proposed work exposed strong self and inter-user interference from the transmitter during demonstrating FD wireless communication mode that destroyed network functionality at the base stations. The occurred self-interference signals from the transmitter are neutralized using precoding and beam-forming technique. During the secondary scenario, decoded base station signals are independently encoded and transmitted to the downlink users. Base stations aid the inter-user interference management by precoding the uplink transmission data and forwarding it to the downlink users. Consequently, the inter-user interference signals are aligned using the span interference alignment technique. A proposed cooperative additional receiver (listener U1) can decode the desired signals and helps in recovering and reconstructing the interference signals. This proposed work completely characterized and evaluated the degree of freedom (DoF) for unknown channel state information at the transmitter (CSIT); whereas achievable lower and upper bound DoF are demonstrated for the partial CSIT. At last, the analytical and simulation results reveal the sum of DoF improvement for unknown and partial CSIT. [ABSTRACT FROM AUTHOR]

This paper studied the physical layer security (PLS) reliability of concurrent wireless communications. A decode and forward (DF) full-duplex (FD) network with the impact of an eavesdropper was proposed to evaluate the security and reliability. Essentially, the DF-FD relay adopted the power-splitting (PS) protocol to gather energy from the source and simultaneously utilized the self-energy recycling (S-ER) technique by manipulating the loopback interference to increase the harvested energy. By constructing closedform expressions for outage probability (OP) and intercept probability (IP), we offer the trade-off analysis between them. Monte Carlo simulation was conducted to verify the analytical formulations. Furthermore, the key parameters were also examined to play an important role in selecting the suitable trade-off for the proposed system. [ABSTRACT FROM AUTHOR]

Abstract Designing circulator as an antenna interface device becomes a daunting task, particularly active‐quasi circulator. This article focuses on demonstrating the basic operation principle, design methods, technical parameters, and performance metrics of active quasi‐circulator. In addition, the study provides an analogy of the circuits and structures proposed by the researchers to enhance certain performance metrics. Active signal cancellation and passive signal cancellation are identified as the major design approaches. Tunable, wideband, and wideband‐tunable are the major types of circulators found in existing literature. Moreover, this article provides a performance comparison of the active‐quasi circulators available in existing literature. Several active quasi‐circulators were able to operate in high frequencies such as 60 GHz with acceptable isolation levels. On the other hand, several designs have over 30 dB isolation, which is a highly desired parameter. At last, the future design challenges associated with active‐quasi circulators have been discussed to provide insight into future research.

This paper considers a full-duplex relay-assisted system for covert communication, in which both the transmitter and the relay are the sender of covert messages. Different from current works that only consider the transmitter power optimization or relay power optimization individually, we propose a joint optimization approach for the transmitter and relay power, which is expected to enhance the system’s covert performance. We establish the minimum error detection probability using the Kullback-Leibler (KL) divergence, which serves as the foundation for formulating our joint optimization problem. The objective is to achieve the highest covert transmission rate within the constraints of covertness requirement and total power limitation. Employing a graphical method, we effectively transform inequality constraints into equality constraints, leading to the derivation of an optimal closed-form solution. The simulation results confirm the accuracy of the theoretical derivation and demonstrate that the proposed power allocation method is effective in determining the optimal power for both the transmitter and the full-duplex relay within a two-hop covert communication system.

This paper presents a compact and planar, in-band full-duplex antenna that offers significant isolation across a broad range of frequencies. In order to attain a wide impedance bandwidth within a limited physical space, two half-resonating modes of a microstrip patch antenna (MPA), namely TM $_{\mathrm {0,3/2}}$ and TM $_{\mathrm {1,1/2}}$ , are stimulated in close proximity. Moreover, the utilization of a parasitic strip that acts as a $\lambda $ /2 resonator, assists in increasing the inter-port isolation. A prototype is fabricated and further measurements indicate that the proposed design offers inter-port isolation better than 30 dB across its wide operating band of 5.95-6.47 GHz, which corresponds to approximately 9% impedance bandwidth ( $\vert $ S $_{11}\vert $ , $\vert $ S $_{22}\vert \lt -10$ dB). Additionally, the prototype exhibited a significant peak gain of 8.2 dBi.

Nonorthogonal multiple access (NOMA) enhances spectral efficiency by enabling manifold devices to utilize the same frequency-time resource through nonorthogonal signal superposition. In addition, full-duplex (FD) transmission allows concurrent reception and transmission on the same frequency range, further improving spectral efficiency. Moreover, nearby wireless energy sources are utilized to enhance energy efficiency. Nonetheless, several challenges are inherent in NOMA FD transmission with energy harvesting (NOFE), including information security concerns and practical imperfections such as channel state information imperfection (CSIi), hardware impairment (HWi), and successive interference cancellation imperfection (SICi). The paper first proposes a solution to address these challenges by leveraging an energy source both as an energy supplier and a jammer to secure transmission under imperfections. The performance of the proposed solution is then evaluated using three key metrics (total throughput, outage probability, energy efficiency). The study highlights the significant impact of various factors such as energy harvesting, HWi, CSIi, NOMA, SICi, and FD on the performance metrics. The proposed solution also aims to prevent complete outage by optimizing required spectral efficiency, HWi, CSIi, SICi and power splitting parameter. Additionally, optimal configuration of system parameters is crucial for achieving optimum performance metrics. Furthermore, the proposed NOFE is demonstrated to be more secured than two benchmark techniques (orthogonal multiple access FD transmission and NOMA half-duplex transmission) across numerous parameter configurations, emphasizing the superiority of utilizing concurrently both NOMA and FD to only either NOMA or FD.

In this paper, a single-antenna full-duplex subsystem is proposed, consisting of a high isolation network and a stacked patch antenna with reflector. The employed patch antenna is fed by two ports with very similar input impedances to make the reflected signals identical. The high isolation network composed of two hybrids and two circulators plays a crucial part in achieving high transmitting to receiving (Tx-Rx) isolation. It is able to cancel out the inevitable reflected signals from the antenna ports and the leakage signals from the circulators. The theoretical analysis is presented and the subsystem is also fabricated and measured. According to the measurement results, across the operation band from 2.018 to 2.12 GHz, the subsystem has VSWR 50 dB, axial ratio 10.2 dBic. Compared with the state-of-art single-antenna full-duplex subsystems, the proposed design features high Tx-Rx isolation level and high gain, which is suitable for microwave radio relay communication and satellite detection application.

This paper presents a novel metamaterial absorber structure for Tx-Rx antenna isolation improvement in the in-band full-duplex massive MIMO systems. The design processes of the absorber unit element, structure and placement, and their impacts on the beamforming radiation patterns are studied. The illustrative result indicates an over 99.8% power absorption at 3.49 GHz. Working with our $8\times 8$ Tx/ $8\times 8$ Rx full-duplex antenna array prototype, an average Tx-Rx antenna element mutual coupling level of -65.4 dB can be achieved between the closest Tx-Rx element pairs, indicating an improvement of 17.5 dB isolation by adding the absorber. The absorber structure’s effectiveness in suppressing beam-level self-interference is studied. The experimental measurement results, utilizing sample Tx/Rx $1\times 8$ antenna sub-arrays, show an average beam-level isolation enhancement of 18.6 dB in near-field coupling dominant scenarios. Integrated with a simple angular perturbation beam isolation technique, an average Tx-Rx beam-level isolation of 90.8 dB and a maximum beam isolation of 104.4 dB can be reached in the Tx/Rx beam steering range −48° to 48° with 20 MHz modulated signals. The experiment illustrates the metamaterial absorber structure has a negligible influence on the far-field beam pattern in the beamforming process. Simulation and measured results on beam radiation patterns and far-field and near-field isolation improvement in different scenarios are investigated and shown to be in good agreement.

In-band full-duplex (FD) operation can double the spectral efficiency of massive multiple-input multiple-output (mMIMO) systems by allowing simultaneous transmission and reception over the same time/frequency slot. However, the main challenge encountered in implementing an FD radio wireless transceiver is to greatly suppress the residual self-interference (SI) generated from its own transmitter below the receiver noise floor to avoid performance degradation in the detection of the signal of interest received from remote transmitters. It is pointed out that the single-stage digital beamforming (DBF) scheme would introduce an impractically high complexity unsuitable for implementing FD-mMIMO. This paper considers an FD hybrid beamforming (FD-HBF) scheme for multi-user (MU)-mMIMO systems, in which large SI-suppression is achieved by exploring dynamic transmitter/receiver (Tx/Rx) isolation using RF-beamforming designs, and exploiting the degrees of freedom of a large number of antenna elements in separate Tx and Rx antenna arrays, in conjunction with high-performance baseband (BB) digital fractionally-spaced (FS) SI-cancellation (SIC) techniques. This paper starts with a discussion of the main parameters and impairments (in an mMIMO transceiver) that can impact the SI-suppression performance and the proposed RF-beamforming Tx/Rx isolation and BB SI-cancellation design strategies along with their achieved performance and complexities. Joint-beamforming optimization to maximize both Tx/Rx performance and isolation is discussed with an example of a nature-inspired optimization scheme to achieve an average Tx/Rx RF isolation of 64.4 dB and the best isolation of 76 dB. The paper continues with a description of an FD-mMIMO transceiver prototype using Tx/Rx 8x8-element antenna arrays along with analytical, simulation and measured results. Illustrative results indicate that the proposed combination of RF-beamforming Tx/Rx isolation and BB digital fractionally spaced SI-cancellation can offer an overall SI suppression of more than 131 dB and bring the residual SI below the receiver noise floor.

A low-profile monolayer dual-port orthomode antenna is presented for enhanced in-band full-duplex (IBFD) communication of wearable biomedical devices. The proposed antenna consists of a center patch surrounded by a complementary slot within a larger peripheral patch. The two ports, which are at opposite lateral sides in a coaxial configuration, are responsible for the Tx/Rx channels respectively. By implementing an asymmetric displacement from the geometric axis, an odd surface current mode is excited via Port 2 (Rx mode), while the even mode is achieved through Port 1 (Tx mode). This mode orthogonality implementation allows a high isolation of > 35 dB between Tx/Rx channels across the central frequency of 6 GHz without circuit elements. In addition, a −10 dB bandwidth of 280 MHz (4.7%) and 480 MHz (8%) is achieved for Port 1 and 2 respectively which supports stable communication channels. The antenna is verified to simultaneously support a unidirectional radiation pattern towards the broadside (Port 1) and a multidirectional hybrid radiation pattern (Port 2) composed of bidirectional $y$ -pol radiation (120° and 60°) as well as broadside $x$ -pol radiation. Both Tx/Rx channels achieve a large front-to-back ratio of > 15 dB. The free space characterization results agree well with the full-wave simulations. Furthermore, the odd/even modes are determined to be stable under local deformations and human loading effects. In conclusion, this monolayer orthomode full-duplex antenna is suitable for various wearable applications due to its low-profile, highly manufacturable design and robustness to environmental imperfections.

The high level of autonomy and intelligence that is envisioned in sixth generation (6G) networks necessitates the development of learning-aided solutions, especially in cases in which conventional Channel State Information (CSI)-based network processes introduce high signaling overheads. Moreover, in wireless topologies characterized by fast varying channels, timely and accurate CSI acquisition might not be possible and the transmitters (CSIT) only have statistical CSI available. This work focuses on the appropriate selection of relaying mode in a cooperative network, comprising a single information source, one buffer-aided (BA) relay with full-duplex (FD) capabilities, and a single destination. Here, prior to each transmission, the relay should select to operate either in FD mode with power control, or, resort to half-duplex (HD) relaying when excessive self-interference (SI) arises. Targeting the selection of the best relaying mode, we propose an FD/HD mode selection mechanism, namely multi-armed bandit-aided mode selection $(\mathop {\mathrm {MABAMS}})$ , relying on reinforcement learning and the processing of acknowledgements/negative-acknowledgements (ACK/NACK) packets for acquiring useful information on channel statistics. As a result, $\mathop {\mathrm {MABAMS}}$ does not require continuous CSI acquisition and exchange and nullifies the negative effect of outdated CSI. The proposed algorithm’s average throughput performance is evaluated, highlighting a performance-complexity trade-off over alternative solutions, based on pilot-based channel estimation that result in spectral and energy costs while obtaining instantaneous CSI.

Full-duplex HCNs have emerged as a compelling solution to meet the escalating traffic demands of future fifth-generation networks. Theoretical advantages of full-duplex cellular networks include the potential for doubling throughput compared to half-duplex cellular systems, as base stations can both receive and transmit within the same frequency band, thereby enhancing various performance metrics. However, in practice, achieving this twofold increase in throughput and maintaining other performance metrics can be challenging due to interference from full-duplex base stations, particularly those of large-scale macro BSs. In this study, we explore a two-tier hybrid duplex HCN architecture, where small-scale BSs operate in full-duplex mode while large-scale BSs and user equipment utilize traditional half-duplex communication. This hybrid approach aims to mitigate interference issues and manage costs effectively. We investigate the impact of various network parameters, coupling scenarios, duplexing modes, and association criteria on the performance of the two-tier HCN. Our simulation results reveal the significant influence of user and small-scale BS densities, as well as the maximum user limit, on binary rate and the Jains fairness index. Remarkably, both binary rate and Jains fairness index exhibit optimal performance at specific values of cell range expansion. In the context of downlink and uplink binary rates, FD and hybrid duplex modes outperform other modes, particularly when the association criterion is based on maximizing average received power. However, when considering the Jains fairness index under the nearest association criteria, half-duplex mode consistently outperforms other modes. This research sheds light on the intricate interplay of duplexing modes, association criteria, and network parameters in the context of FD HCNs, providing valuable insights for optimizing network performance in the era of 5G and beyond.

A high isolation antenna is presented which offers dual-polarization monopulse beam patterns, making the design suitable for polarization diverse or full-duplex (FD) systems. The single-layer structure is defined by a network of 2-D sub-arrays oriented in a cross-shape configuration using series-fed slots in substrate integrated waveguide (SIW) technology. Also, the proposed design exploits dual-differential feeding to achieve a −10 dB impedance matching bandwidth (BW) from 23.2 GHz to 25.4 GHz, and measured isolation values are more than 70 dB (peaking to about 90 dB) over this same operating range. Realized gain values are 13 dBi (and above) while cross-polarization values are less than 35 dB below the beam maximum. The novelty in the design can be defined by the inclusion of a simple SIW isolation element at the center of the antenna structure. This provides enhanced isolation and enables co-location for the vertical and horizontal SIW sub-array branches, and this simple and low-profile arrangement supports efficient dual-linear polarized radiation. To the best knowledge of the authors, no similar 2-D planar antenna design has been previously reported offering high isolation in the K-band and which can offer sum and difference beam patterns in the far-field (FF). Some applications include monopulse tracking setups for communications as well as in-band FD systems which require dual-polarization at microwave and millimeter-wave frequencies.

This paper introduces a novel spatial domain-based self-interference cancellation (SIC) method named constrained minimum mean square error (C-MMSE) for massive multiple-input multiple-output (mMIMO) full-duplex (FD) communication systems. The main idea involves treating the self-interference (SI) signal emitted from an FD node as a distinct spatial stream arriving at the receiver part of that same FD node. This SI signal needs to be spatially postcoded alongside other relevant signals coming from different transmitters, ensuring it falls into the null space of the MIMO channel, which includes the FD node transmitter part as an input. To establish this approach, we first adapt the expressions of spatial combiners for conventional zero forcing (ZF) and minimum mean square error combining (MMSE) criteria. We demonstrate that MMSE alone is insufficient for efficient SI signal cancellation unless an additional constraint is added to enable proper SIC. Consequently, we design the innovative C-MMSE combiner and derive its expression. In addition to our proposal, the originality of our work stems from employing a spherical wave model (SWM) to model the SI channel. The choice is justified by the proximity of the transmit and receive antenna panels in the FD node. We examine and compare the SIC performance of the modified ZF combiner, the modified MMSE combiner, and the newly introduced C-MMSE combiner by evaluating the spectral efficiency (SE). Additionally, we highlight the robustness of the SWM-based SI channel modeling in comparison to conventional planar wave modeling (PWM), emphasizing the relevance of its usage.

Integrated access and backhaul (IAB) networks operating in full-duplex (FD) mode at millimeter wave frequencies have been actively investigated in the context of future-generation communications networks. However, conventional analog cancellation techniques cannot adequately mitigate the self-interference resulting from the FD operation and the multi-user interference. Hence, in this paper, we consider a multi-cell, multi-user IAB network and jointly design the beamforming and combining matrices to maximize the network’s weighted sum rate. Given the non-convex nature of the problem, we reformulate it using weighted minimum-mean-square-error (WMMSE) and extended fractional programming (FP) techniques followed by a block coordinate descent (BCD) approach. Extensive simulation results validate the superior performance of our proposed algorithms. Specifically, the WMMSE and FP methods can achieve 50 bits/sec/Hz higher than the benchmark scheme for a network employing three cells with two uplink and two downlink users per cell.

This article evaluates performance metrics in terms of outage probability (OP), throughput, and energy efficiency (EE) of the reconfigurable intelligent surface (RIS) assisted full-duplex (FD) wireless communication systems under the joint and separate effects of imperfect conditions such as residual transceiver hardware impairments (RTHIs) and residual self-interferences (SIs). More specifically, we derive the exact formulas of OP, throughput, and EE of the RSI-aided-FD systems with the joint effects of RTHIs and residual SIs. From the obtained expressions, it is easy to formulate the formulas of the relevant systems such as RIS-aided-FD systems without RTHIs and RIS-aided-half-duplex (HD) systems without and with RTHIs. Numerical illustrations clarify the huge impacts of RTHIs and residual SIs on the OP, throughput, and EE of the RIS-aided-FD systems, especially in the high data rate. In this situation, utilizing a large number of reflecting elements (REs) can dramatically enhance the OP, throughput, and EE performance of the RIS-aided-FD systems with RTHIs and residual SIs. Finally, the derived formulas are validated by using Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

In order to optimize the energy efficiency and spectral efficiency of decoded-and-forwarded full-duplex relay network in imperfect channel state information, this paper proposed an energy efficiency and spectral efficiency balancing strategy based on this network model. It could replace the non-convex multi-objective optimization problem to a convex single-objective optimization problem by constructing a compromise optimization function of energy efficiency and spectral efficiency. It used derivation method and Lagrange multiplier method to solve the optimal relay transmission power under different compromise factors. The simulation results show that changing the compromise factor can change the energy efficiency and spectral effectiveness of the system and obtain the performance tradeoff of energy efficiency and spectrum effectiveness. [ABSTRACT FROM AUTHOR]

This paper examines the performance of Full-Duplex Cooperative Rate Splitting (FD-CRS) with Simultaneous Wireless Information and Power Transfer (SWIPT) support in Multiple Input Single Output (MISO) networks. In a Rate Splitting Multiple Access (RSMA) multicast system with two local users and one remote user, the common data stream contains the needs of all users, and all users can decode the common data stream. Therefore, each user can receive some information that other users need, and local users with better channel conditions can use this information to further enhance the reception reliability and data rate of users with poor channel quality. Even using Cell-Center-Users (CCUs) as a cooperative relay to assist the transmission of common data can improve the average system speed. To maximize the minimum achievable rate, we optimize the beamforming vector of Base Station (BS), the common stream splitting vector, the cooperative distributed beam vector and the strong user transmission power under the power budget constraints of BS and relay devices and the service quality requirements constraints of users. Since the whole problem is not convex, we cannot solve it directly. Therefore, we propose a low complexity algorithm based on Successive Convex Approximation (SCA) technology to find the optimal solution to the problem under consideration. The simulation results show that FD C-RSMA has better gain and more powerful than FD C-NOMA, HD C-RSMA, RSMA and NOMA. [ABSTRACT FROM AUTHOR]

D2D communication is a promising technology for enhancing spectral efficiency (SE) in cellular networks, and full-duplex (FD) has the potential to double SE. Due to D2D's short-distance communication and low transmittance power, it is natural to integrate FD into D2D, creating FD-D2D to underlay a cellular network to further improve SE. However, the residual self-interference (RSI) resulting from FD-D2D and interference arising from spectrum sharing between D2D users (DUs) and cellular users (CUs) can restrict D2D link performance. Therefore, we propose an FD-D2D underlying cellular system in which DUs jointly share uplink and downlink spectral resources with CUs. Moreover, we present two algorithms to enhance the performance experience of DUs while improving the system's SE. For the first algorithm, we tackle an optimization problem aimed at maximizing the sum rate of FD-DUs in the system while adhering to transmittance power constraints. This problem is formulated as a mixed-integer nonlinear programming problem (MINLP), known for its mathematical complexity and NP-hard nature. In order to address this MINLP, our first algorithm decomposes it into two subproblems: power control and spectral resource allocation. The power control aspect is treated as a nonlinear problem, which we solve through one-dimensional searching. Meanwhile, spectral resource allocation is achieved using the Kuhn–Munkres algorithm, determining the pairing of CUs and DUs sharing the same spectrum. As for the second algorithm, our objective is to enhance the individual performance of FD-DUs by maximizing the minimum rate among them, ensuring more uniform rate performance across all FD-DUs. In order to solve this optimization problem, we propose a novel spectral resource allocation algorithm based on bisection searching and the Kuhn–Munkres algorithm, whereas the power control aspect remains the same as in the first algorithm. The numerical results demonstrate that our proposed algorithm effectively enhances the performance of DUs in an FD-D2D underlying cellular network when compared to the sum rate maximization design. [ABSTRACT FROM AUTHOR]

A new method for capacity and spectral efficiency increases is a full-duplex communication, where sending and receiving are done simultaneously. Hence, severe interference leaked from the transmitter to the receiver, which can disrupt the system's operation completely. For interference reduction, the transceiver tries to estimate the interfering symbols to remove their effects. A typical method is to use the Hammerstein model. In this method, nonlinear power amplifier (PA) and multipath channel are modeled with a successive nonlinear system and a finite impulse response filter. Then, the model parameters are adjusted, and interference symbols are estimated from the transmitted symbols. In the Hammerstein method, the interference symbols are estimated directly from the transmitted symbols. But practically, the transmitted symbols first pass through the pulse-shaping filter and become a signal. Then, this signal passes through the nonlinear PA and communication channel. Finally, the received signal is filtered by the matched filter (MF) at the receiver and converted to the symbols again. In this procedure, the amplifier and the communication channel affect the transmitted signal directly and distort transmitted symbols indirectly. Therefore, in the practical situation, when we consider the transmitter's pulse-shaping filter and the receiver's MF, the estimated symbols with the Hammerstein method are erroneous. To solve this problem, a new MF at the receiver is proposed and adjusted according to the interfering signal. We have shown that this method is far better than the Hammerstein method. [ABSTRACT FROM AUTHOR]

Device-to-Device (D2D) communication has received increasing attention and been studied extensively thanks to its advantages in improving spectral efficiency and energy efficiency of cellular networks. This paper proposes a novel relay selection algorithm for multi-hop fullduplex D2D communications underlaying cellular networks. By selecting the relay of each hop in a reverse manner, the proposed algorithm reduces the heavy signaling overhead that traditional relay selection algorithms introduce. In addition, the social domain information of mobile terminals is taken into consideration and its influence on the performance of D2D communications studied, which is found significant enough not to be overlooked. Moreover, simulations show that the proposed algorithm, in absence of social relationship information, improves data throughput by around 70% and 7% and energy efficiency by 64% and 6%, compared with two benchmark algorithms, when D2D distance is 260 meters. In a more practical implementation considering social relationship information, although the proposed algorithm naturally achieves less throughput, it substantially increases the energy efficiency than the benchmarks. [ABSTRACT FROM AUTHOR]

This paper investigates the adverse effects of co-channel interference (CCI) on the secrecy achievable rate (SAR) performance of illegitimate decode-and-forward full-duplex two-way relaying in power-domain non-orthogonal multiple access network. So as to minimize the information leakage, the investigation considers that illegitimate relay terminals are affected by a limited number of friendly jammers. In an effort to minimize the system overhead, the investigation activates a single illegitimate relay terminal by selecting a relay, which has the minimum secrecy achievable rate and maximizing. Obtained results reveal that while the CCI has adverse effects on system SAR performance, the friendly jammer helps to enhance the system performance. Monte-Carlo-based extensive simulations verify the numerically obtained results. [ABSTRACT FROM AUTHOR]