The rapid evolution of mobile technologies presents a formidable security challenge, as traditional cryptographic methods struggle to keep pace. Integrating physical layer security (PLS) solutions with cutting-edge technologies such as in-band full-duplex (IBFD) and reconfigurable intelligent surfaces (RISs) holds promise for addressing these challenges effectively. This study introduces a novel RIS-driven protected zone (PZ) formation approach that employs artificial noise (AN) to safeguard legitimate users without requiringa prioriknowledge of eavesdropper locations, channels, or numbers. The proposed methodology partitions the RIS into two distinct segments: while the former segment enhances the achievable data rate for legitimate signal, the latter segment concurrently amplifies AN to jam illegitimate users within the PZ.We present formulations and solutions for maximizing secrecy capacity (SC) and minimizing power consumption through optimized transmit power allocation factors, RIS segmentation, and beams’ directions, all subject to stringent quality-of-service (QoS) constraints. Closed-form expressions are derived to facilitate efficient implementation and performance optimization. Simulation results validate closed-form solutions and demonstrate that the proposed scheme can significantly enhance SC compared to benchmarks where RIS and AN are used separately, with the proposed scheme achieving approximately 81% greater capacity than the “RIS-Only” approach and a substantial advantage over the “AN-Only” approach, which results in no secrecy. Additionally, this work includes an analysis of energy efficiency, emphasizing the critical importance of optimizing power consumption in practical applications. This dual focus on improving security while effectively managing energy resources underscores the scheme’s practical relevance and efficiency.

The rapid proliferation of mobile technologies introduces substantial security vulnerabilities, with conventional cryptographic approaches increasingly inadequate. Physical layer security (PLS) approaches, especially when paired with advanced methods like full-duplex (FD) communication and reconfigurable intelligent surfaces (RISs), offer substantial potential for enhanced security. This work proposes a novel RIS-aided inband FD (IBFD) framework that employs artificial noise (AN) to establish a protected zone (PZ) around the legitimate user, operating independently of any a priori knowledge regarding the number, positions, or channels of potential eavesdroppers. To achieve this, the RIS is functionally partitioned into two distinct segments: one enhances the legitimate user's data rate, while the other simultaneously intensifies AN to jam any unauthorized users within the PZ. We formulate a secrecy capacity (SC) maximization problem that optimizes both the legitimate user's transmission power and the RIS configuration, while meeting quality-of-service (QoS) requirements. Simulation results indicate the superior efficacy of the proposed technique in enhancing SC compared to benchmarks that employ RIS and AN independently. In particular, the proposed approach achieves an approximate SC improvement of 80% and 49% over the “RISonly” and “AN-only” approaches, respectively, underscoring its significant potential to enable robust PLS in next-generation communication networks.

The incorporation of reconfigurable intelligent surfaces (RISs) and unmanned aerial vehicles (UAVs) presents considerable potential for improving the functionality of ground-based terrestrial Internet of Things (IoT) networks. This paper introduces a novel UAV deployment and aerial RIS partitioning mechanism for the uplink non-orthogonal multiple access (NOMA)-based IoT networks under practical hardware constraints. The low-cost hardware of IoT devices results in imperfect successive interference cancellation (SIC) and distortion noise due to transceiver hardware impairments (T-HIs). Specifically, we have optimized the aerial RIS partitioning and its deployment to maximize the minimum rate under the impact of imperfect SIC and T-HIs. The numerical results show that the proposed scheme outperforms the benchmark. Through extensive simulations, we prove that the proposed UAV-based aerial RIS-aided uplink NOMA network significantly enhances the max-min fair rate.

This work investigates simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS) in multiple-access (MA) bidirectional network architecture. The proposed optimization framework incorporates two practical operational protocols of STAR-RIS to optimize the channel gains for users and obviate the necessity for uplink power control while adhering to specified quality of service (QoS) constraints. The proposed approach undergoes thorough evaluation under key optimization problems: QoS feasible region, and energy efficiency. The closed-form solutions are validated through simulations, showcasing the notable advantages that STAR-RIS can provide to the considered multiple-access networks. Simulation findings revealed that in the context of the proposed system model, the mode switching approach can attain a superior QoS threshold rate compared to the energy splitting mode. The proposed framework has demonstrated its ability to meet bidirectional communication needs with a high degree of accuracy and precision.

In this work, we examine the potential of reconfigurable intelligent surfaces (RISs) to facilitate and enhance uplink (UL) transmissions in grant-free non-orthogonal multiple access (GF-NOMA) networks. The proposed RIS-assisted GF-NOMA approach employs virtual partitioning of RIS, with each partition tailored to optimize channel conditions for individual NOMA user equipment (UE). The resulting channel gain disparity bolsters the NOMA gain and obviates the necessity for UL power control of the grant-based NOMA schemes. Our approach is evaluated under three practical operational regimes: 1) quality-of-service (QoS) sufficient regime, 2) efficient RIS usage regime, and 3) max-min fair regime, all subject to UL-QoS constraints. We derive closed-form solutions to elucidate how optimal RIS partitioning can fulfill UL-QoS requirements across all three operational regimes. Comprehensive simulations are conducted to validate the precision of our analytical findings, demonstrating that the proposed approach substantially improves wireless communication system performance while mitigating signaling overhead and computational complexity.

Terahertz (THz) communication with a Tbps transmission rate requires novel channel propagation models and designs for antennas and RF components to address the challenges in THz bands, including molecular absorption effects, high penetration loss, and frequent blockages. An extreme data rate, ultra-low latency, and cm-level localization in the THz band will accelerate a massive deployment of IoT devices, where device nodes may re-transmit other users’ messages. In this work, we study a THz cooperative network with an N-relay decode-and-forward relay selection scheme, where users are equipped with a fluid antenna system (FAS) receiver technology. FAS offers paramount flexibility and numerous advantages, especially for biomedical applications. Moreover, the proposed system considers non-ideal transceiver hardware that emits residual transceiver hardware impairments (RTHI) noise that notably deteriorates the performance of high-rate networks. Existing research often focuses on ideal transceiver hardware, overlooking the impact of RTHI noise. As a result, we introduce a rapidly converging semi-infinite expression for the coverage probability (CP), validated through extensive Monte Carlo simulations. The results highlight a substantial degradation in the CP performance with each distance meter. Thus, deploying devices for relaying messages and employing FAS receivers significantly enhance the CP performance.

This study delves into the capabilities of reconfigurable intelligent surfaces (RISs) in enhancing bidirectional non-orthogonal multiple access (NOMA) networks. The proposed approach partitions RIS to optimize the channel conditions for NOMA users, improving NOMA gain and eliminating the requirement for uplink (UL) power control. The proposed approach is rigorously evaluated under four practical operational regimes; 1) Quality-of-Service (QoS) sufficient regime, 2) RIS and power efficient regime, 3) max-min fair regime, and 4) maximum throughput regime, each subject to both UL and downlink (DL) QoS constraints. By leveraging decoupled nature of RIS portions and base station (BS) transmit power, closed-form solutions are derived to show how optimal RIS partitioning can meet UL-QoS requirements while optimal BS power control can ensure DL-QoS compliance. Analytical findings are validated by simulations, highlighting the significant benefits that RISs can bring to the NOMA networks in the aforementioned operational scenarios.

Reconfigurability and innovative design approaches to radio frequency components and network infrastructure are critical for the development of future communication networks, particularly beyond 5G (B5G), which aim to support the proliferation of Internet of Things (IoT) devices. Leveraging its favorable performance characteristics and potentially low cost, the fluid antenna system (FAS) has emerged as a compelling solution, garnering significant interest due to its reconfigurability, small form factor, flexibility, and transparency. This paper presents a comprehensive analysis of FAS in the context of B5G networks, with a focus on its theoretical performance and practical implementations. By deriving formulas for the semi-infinite outage probability and ergodic capacity of FAS receivers in equally correlated Nakagami-m channels, we showcase the remarkable diversity performance exhibited by FAS receivers, even with a half-wavelength antenna size. Monte Carlo simulations are employed to validate our theoretical findings in terms of the number of antenna ports and transmission power.

Millimeter-wave networks have already been successfully rolled out in many countries and now the research direction heads toward new technologies and standards to enable Tbps rates for future sixth-generation (6G) wireless communication systems. This work studies a point-to-point terahertz (THz) communication network exploiting the concept of a fluid antenna system (FAS) over correlated alpha-mu fading channels, nicely fitting the THz communication. Furthermore, the considered system is expanded to the selection-combining-FAS (SC-FAS) and maximum-gain-combining-FAS (MGC-FAS) diversity variates at the receiver side. The proposed FAS and its diversity configuration techniques are aimed to combat the high path loss, blockages, and molecular absorption effect related to the THz band. Our contribution includes comprehensive outage probability (OP) performance analysis for the THz band given the non-diversity and diversity FAS receivers. Moreover, the derived outage probability formulas are verified via Monte Carlo simulations. Numerical results have confirmed the superior performance of the MGC-FAS scheme in terms of OP. Finally, this work justifies that a higher number of antenna ports dramatically improves the system performance, even in the presence of correlation.

Intelligent surfaces have recently been presented as a revolutionary technique and recognized as one of the candidates for beyond fifth-generation wireless networks. This paper investigates the physical layer security of a large intelligent surface (LIS) aided wireless system over Nakagami-m channels. We propose a phase-based adaptive modulation scheme, where LIS’s phase-shift optimization process is effectively utilized to enhance the system’s security. Moreover, the effect of the Nakagami-m fading parameter (m), correlation parameter ($\rho$), and a number of passive LIS elements (M) on the system performance are examined. The significant improvement in confidentiality is shown while evaluating the bit error rate performance of the proposed scheme.

Reconfigurable intelligent surfaces (RISs) have sparked a renewed interest in the research community envisioning future wireless communication networks. In this study, we analyzed the performance of RIS-enabled non-orthogonal multiple access (NOMA) based device-to-device (D2D) wireless communication system, where the RIS is partitioned to serve a pair of D2D users. Specifically, closed-form expressions are derived for the upper and lower limits of spectral efficiency (SE) and energy efficiency (EE). In addition, the performance of the proposed NOMA-based system is also compared with its orthogonal counter-part. Extensive simulation is done to corroborate the analytical findings. The results demonstrate that RIS highly enhances the performance of a NOMA-based D2D network.

Fluid antenna systems (FAS) enable mechanically flexible antennas that offer adaptability and flexibility for modern communication devices. In this work, we present a conceptual model for a single-antenna N-port (SANP) FAS over spatially correlated Nakagami-m fading channels and compare it with the traditional diversity schemes in terms of outage probability. The proposed FAS model switches to the best antenna port and resembles the operation of a selection combining (SC) diversity. FAS improves the quality of service (QoS) of the network through antenna port selection. The advantage of FAS is the ability to fit hundreds of antenna ports into a half-wavelength antenna size at the cost of spatial channel correlation. Simulation results demonstrate the superior outage probability performance of FAS at several tens of antenna ports compared to the traditional diversity schemes such as maximum ratio combining, equal gain combining, and SC. Moreover, the novel probability and cumulative density functions for the land mobile correlated Nakagami-m random variates are evaluated in this paper.

In this paper, we investigate a non-orthogonal multiple access (NOMA) assisted cognitive satellite-terrestrial network under practical system conditions, such as transceiver hard-ware impairments, channel state information mismatch, imperfect successive interference cancellation and interference noises. Generalized coverage probability formulas for NOMA users in both primary and secondary networks are derived considering the impact of interference temperature constraint. Moreover, the numerical results demonstrate superior outperformance compared to the ones obtained for an orthogonal multiple access scheme. Finally, the derived analytical findings are fully supported by thorough Monte Carlo simulations.

In this paper, we study a cognitive hybrid satellite-terrestrial relay network with imposed practical limitations, such as channel state information mismatch and transceiver-induced hardware impairments. Moreover, it is assumed that the network undergoes multiple independent and non-identically distributed interference noises arising from neighboring transmitters. Generalized closed-form expressions of the outage probability for a terrestrial user are obtained while taking into account the effect of an interference temperature constraint. Finally, analytical derivations are verified through Monte Carlo simulation and the impact of impairments is examined.

In this paper, we analyze the system performance of a large intelligent surface (LIS) enabled wireless system over Nakagami-m channels. We derive closed-form expressions of the outage probability, ergodic capacity, and average bit error rate using different approximation methods, namely, central limit theorem (CLT), Gamma and generalized-K$(K_{\mathrm{G}})$. The effects of a number of passive LIS pixels$(N)$and fading parameters on the system performance are examined. Results show that the Gamma and$K_{\mathrm{G}}$approximations are precise given different values of$N$, while the CLT approximation's accuracy depends on the number of LIS elements implemented. Finally, analytical findings are validated by thorough Monte Carlo simulations.

In this paper, the outage probability (OP) of the two-hop cooperative non-orthogonal multiple access network with an energy-constrained cooperative agent is evaluated over generalized α-µ and κ-µ fading models. The power splitting relaying protocol is implemented at the cooperative agent, acting as a relay in amplify-and-forward mode. The effect of hardware impairments (HIs) at the radio frequency front-ends of transceivers are incorporated during the performance evaluation. The results based on the derived analytical expressions suggest the importance of considering HIs for given network architecture and allow one to evaluate the OP over various statistical models.

This paper investigates a non-orthogonal multiple access (NOMA) assisted cognitive satellite-terrestrial network which is practically limited by interference noises, transceiver hardware impairments, imperfect successive interference cancellation, and channel state information mismatch. Generalized outage probability expressions for NOMA users in both primary and secondary networks are derived considering the impact of interference temperature constraint. Finally, obtained results are corroborated by Monte Carlo simulations and compared with the orthogonal multiple access to show the superior performance of the proposed network model.

This paper provides a performance evaluation of two-hop non-orthogonal multiple access (NOMA) architecture with energy harvesting (EH) cooperative agent and channel gains following the k-m fading, through analysis of ergodic capacity with respect to hardware impairments and channel conditions. The performance results of the distant user over two EH protocols, namely power splitting and time-switching relaying, are obtained and compared with simulation outcomes. The developed framework allows to evaluate the network under a range of external conditions and infers the importance of considering the hardware impairments.

Non-orthogonal multiple access (NOMA) is considered to be one of the promising multiple access techniques for 5G networks. This paper studies a decode-and-forward cooperative underlay cognitive radio NOMA network. Closed-form expressions for the outage probability of two NOMA secondary destination users (D1and D2) are evaluated. Furthermore, optimal power allocation factors for different distances of D1are found to satisfy the outage probability (OP) fairness for both users. Moreover, the OP for NOMA compared to that of conventional multiple access. Finally, the obtained analytical expressions are corroborated by Monte Carlo simulation.

In this paper, a two-hop decode-and-forward wireless powered relaying cognitive radio network with interference alignment over Rayleigh fading channels is investigated. The energy-constrained secondary relay node harvests energy from both the information and interference signals. Then, the harvested energy is used by the relay to forward the information signal from the source to the destination node. By applying beamforming matrices to primary and secondary networks, the performance metrics, such as outage probability, capacity, and bit error rate are studied under perfect and imperfect channel state information scenarios for both power-splitting relaying (PSR) and time-switching relaying (TSR) protocols. In addition, the optimal network performance is achieved by calculating the optimal energy harvesting time-switching and power-splitting coefficients. Finally, closed-form expressions for the outage probability of primary and secondary users are derived. Monte Carlo simulation results corroborate the analytical ones and show that the PSR technique outperforms TSR in the considered system model.

In this paper, a two-hop decode-and-forward cognitive radio system with deployed interference alignment is considered. The relay node is energy- constrained and scavenges the energy from the interference signals. In the literature, there are two main energy harvesting protocols, namely, time-switching relaying and power-splitting relaying. We first demonstrate how to design the beamforming matrices for the considered primary and secondary networks. Then, the system capacity under perfect and imperfect channel state information scenarios, considering different portions of time-switching and power-splitting protocols, is estimated.

This paper studies a two-hop decode-and-forward underlay cognitive radio system with interference alignment technique. An energy-constrained relay node harvests the energy from the interference signals through a power-splitting (PS) relaying protocol. Firstly, the beamforming matrices design for the primary and secondary networks is demonstrated. Then, a bit error rate (BER) performance of the system under perfect and imperfect channel state information (CSI) scenarios for PS protocol is calculated. Finally, the impact of the CSI mismatch parameters on the BER performance is simulated.