Millimeter-wave rate-splitting multiple access (mmWave-RSMA) technology combines the wideband characteristics of millimeter waves with the rate-splitting mechanism of RSMA, significantly improving the communication efficiency of the system. However, this feature also poses greater challenges to its secure transmission, especially in networks with dual-identity nodes which act as legitimate users while also being able to eavesdrop on information from other users. This behavior will simultaneously weaken the security of both public and private streams. In this regard, the active reconfigurable intelligent surface (RIS) offers a promising method by suppressing eavesdropper channels and enhancing the quality of legitimate links. Focusing on the physical layer security (PLS) challenge posed by dual-identity users in mmWave-RSMA networks, this paper proposes an active RIS assisted secure beamforming scheme integrated with resource allocation optimization. Specifically, while ensuring the quality of service (QoS) for dual-identity user and power amplification constraints of the active RIS, the sum secrecy rate is maximized by jointly optimizing the transmit beamforming vector, reflection coefficient matrix, common rate allocation, and power allocation coefficients. To solve this non convex problem, we divide it into three subproblems. Then, successive convex approximation (SCA) and semidefinite relaxation (SDR) are used to solve these subproblems. Simulation results validated the critical role of active RIS in reducing eavesdropping, and emphasized the importance of joint resource allocation for secure beamforming in mmWave-RSMA.

Fluid antennas (FA) offer a revolutionary breakthrough in wireless communications by dynamically regulating antenna positions within confined spaces to significantly enhance system capacity and link reliability. In this paper, a FA integrated and reconfigurable intelligent surface empowered receive spatial modulation (FA-RIS-RSM) scheme is proposed. Specifically, due to the unique physical properties of FA, we propose two port selection strategies, namely the random port selection (RPS) and optimal port selection (OPS), to assist the transmission achieving with distinct extents of reliability. Furthermore, we derive closed-form expressions for the average bit error probability (ABEP), via utilizing the Gamma approximation analysis and correlated fading analogism analysis methods, respectively. Simulated and numerical performance results corroborate the correctness of the derivations, as well as demonstrate the superiority and effectiveness of the proposed FA-RIS-RSM in enhancing the wireless transmission reliability.

To address the physical layer security issues for the next generation wireless, we introduce and investigate a novel fluid antenna assisted secure joint transmitter-spatial and receiver-port index modulation (FA-SJIM) system. Specifically, we detail two schemes to enhance both the transmission efficiency and secrecy. The schemes are based on the continuous random phase and discrete random phase distortions at the transmitter and the constructive phase-aligning manipulations at the RIS, respectively. Furthermore, we derive the semi-closed-form secrecy outage probability (SOP) results of the proposed schemes with the maximum likelihood detection, so as to facilitate the evaluation of the system secrecy. Finally simulated and numerical performance results are characterized to reveal the high accuracy of SOP derivations, and the superiority of the FA-SJIM in terms of transmission efficiency and secrecy.

To address the increasing demand for transmission systems with enhanced efficiency and flexibility, two-way (TW) full-duplex (FD) systems have become a vital research focus in wireless communications. In this paper, a novel reconfigurable intelligent surfaces (RISs) assisted TW-FD spatial modulation (SM) model is proposed to improve the transmission reliability performance. With this proposal, we introduce the transmit-side SM to activate single antenna for fulfilling the transmission of amplitude and phase modulated symbols. The transmission is then reflected by the corresponding RIS to the antenna at the receiver end. Moreover, the prewired phase-offset (PPO) is included in the transmission process for attaining enhanced detecting reliability. To evaluate the performance boundaries of the proposed system, we consider the maximum likelihood detection based analytical derivations. More specifically, upon utilizing the moment generating function method, we derive the closed-form results for the system average bit error probability. Finally, with the simulation based comparative analysis, we verify the reliability and efficiency of the proposed TW-FD-RIS-PPOSM system.

In this paper, we investigate a hybrid reconfigurable intelligent surface (RIS) enabled integrated sensing and commu-nication (ISAC) system, in which a hybrid RIS is employed to assist a base station (BS) to sense a specified target, while interacting with multiple communication users (CUs) simultaneously. In particular, a hybrid RIS is introduced such that each of its surface module is able to switch between active and passive modes, reducing the system's power consumption. Subsequently, an optimization problem is formulated with the aim of maximizing the radar output signal-to-noise ratio while satisfying communication requirement for each CU, transmit power constraint for BS and the active RIS elements, by jointly optimizing radar recieve filter, BS's transmit beamforming matrix, RIS reflection coefficients, and the selection matrix that determines the working modes for each unite of the hybrid RIS. Since this design problem is not convex, we propose an alternating optimization based method to solve this problem. Eventually, upon the simulation analysis, we demonstrate that the performance achievable by the proposed scheme is significantly better than the counterparts assisted solely by the active or passive RIS.

This article investigates the covert performance of the finite block length device-to-device (D2D) transmission between the multiantenna transceivers assisted by a decode-and-forward (DF) relay node, where the adversary in covert communication, the warden, also employs a multiantenna maximum likelihood detector which observes the covert signals from the source and the relay for joint detection. The relay periodically transmits reference signals to improve the throughput rate over the fading channels while the source and destination estimate the channel coefficients for beamforming. The nonideal beamforming performance with limited reference signals is analyzed, the covert performances measured by the expected relative entropies of the warden’s joint detection are derived, and the optimal power allocation strategy to achieve the highest covert performance under the required throughput rate and outage probabilities is formulated in this article. The theoretical analysis and the numerical results illustrate that the communication side will achieve higher covertness if the relay and the source adopt uncorrelated codes, and the increase in the warden’s antenna number would rapidly improve its detection performance. The numerical results also depict that enhancing the source-to-relay covert transmission brings more improvements for the covertness than the relay-to-destination link, showing the asymmetry between the different links of the DF-relay-assisted covert communication.

With the emergence of the fifth generation (5G) era, the development of the Internet of Things (IoT) network has been accelerated with a new impetus, making it imperative to strive for a more reliable and efficient network environment. To accomplish this, we introduce and investigate a novel proposal for the intelligent reflecting surface (IRS) enabled uplink secure receive spatial modulation (SM), named IRS-USRSM, to resolve the security issues arising from the open wireless transmission environment in the 5G IoT network. In the IRS-USRSM scheme, we assume that the passive eavesdropper is directly connected to the uplink user and occasionally connected to the IRS. To achieve enhanced secrecy with finite alphabet inputs, a joint transmitter perturbation and IRS reflection design for physical layer security is proposed to guarantee secure and reliable transmission of IRS-USRSM. Specifically, two categories of IRS-based random phase compensation strategies, namely, random perturbation compensation and random path synthesize, along with maximum likelihood detection and suboptimal detection are proposed to meet the variant design requirements between achieved performance and system cost. Furthermore, in order to evaluate the performance limits of the IRS-USRSM, the closed-form results of average bit error probabilities and discrete-input continuous-output memoryless channel capacities are derived using the method of moment generating function. Simulation results are presented to verify the correctness of our theoretical analyses, as well as to demonstrate the efficiency and superiority of the proposed IRS-USRSM scheme.

Covert wireless communication intends to prevent hostile surveillance but is threatened by the powerful multi-antenna detection technique. In this paper, we investigate finite blocklength covert communication assisted by a multi-antenna relay station and a multi-antenna destination to fight against hostile detection from a warden also equipped with multiple antennas and interference from an uninformed jammer. In order to achieve optimal covert communication performance, we formulate the optimization problems in the single-user and the frequency division multiple access (FDMA) multi-user scenarios separately. In the single-user scenario, we design a cooperative beamforming strategy for the relay and the destination to maximize their received signal-to-interference-plus-noise (SINR). Then in the multi-user scenario, we utilize the above beamforming strategy and propose a majorization-minimization-based relay’s power allocation algorithm to maximize the total covert throughput rate. The numerical results are provided to depict the effectiveness of the proposed scheme, and we address how the jamming power and the numbers of antennas affect covert communication based on these numerical results and theoretical analysis.

In this paper, we address finite block-length covert wireless communication against an adversary that not only detects the signals but also localizes the source. Because of the probability of failed localization, the adversary’s detection strategy differs greatly from the former works. In the free space propagation model, we discuss the surveillance strategy of an adversary equipped with a uniform linear antenna array and the legitimate users’ resources optimization scheme for achieving covert communication. The theoretical analysis and the numerical results illustrate the properties of the adversary’s surveillance and the achievable covert communication performance, showing that the randomness in the source’s transmission time may also improve the covertness.

To address the security issues in wireless transmission communication systems with finite-alphabet inputs, a secure uplink reception scheme based on receiver spatial modulation is proposed to ensure high security of the wireless transmission system while achieving high spectrum efficiency. The proposed scheme introduces disturbance phase updates at the transmitter end and disturbance compensation at the intelligent reflecting surface (IRS) to ensure both the spectrum efficiency and physical layer security of the wireless transmission system. This enables the legitimate receiver to correctly receive the signal at maximum power while preventing eavesdroppers from accurately intercepting the signal. In this paper, we propose two phase compensation schemes, namely, element-wise random disturbance compensation (ERDC) and group-wise random disturbance compensation. Furthermore, two eavesdropping scenarios, referred to as ideal eavesdropping and jamming eavesdropping, are thoroughly investigated and considered. We introduce the maximum likelihood detection to reliably detecte the indices of the designed receive antenna and the based-band modulated signal, and the closed-form expressions of error performance with ERDC scheme are deduced. Finally, in the simulated and numercial results, the performance analysis verifies error performance discrepancy based security performance evaluation of the proposed scheme, demonstrating its effectiveness and superiority.

Reconfigurable intelligent surface (RIS) assisted spatial-domain pattern index modulations (PIMs) are recently emerged as promising transmission candidates for the next generation wireless. In this research, we are motivated to investigate a novel augmented PIM (APIM) framework empowered by RIS, such that the potentials of PIM and RIS can be merged for realizing energy efficient high data rate transmissions. In contrast to the spatial-domain PIM, the proposed APIM is implemented by utilizing the indices of activated patterns of the transmitter, receiver and the RIS to modulate information. To maximize the signal power observed with the desired receive pattern, the element-wise and subset-wise phase alignment based reflection designs are provided for the RIS, which may be imposed with different requirements regarding the reflection implementation complexity. Based on the principle of maximum-likelihood estimation, we introduce the optimal joint detection (OJD) to accomplish detecting of APIM signals. Furthermore, we analyze the error and capacity performance of the APIM systems employing the OJD, so as to evaluate the performance limits achievable by the proposed APIM. Finally, simulation results demonstrate the efficiency of our APIM scheme and verify the accuracy of the performance evaluation.

In order to enhance the secrecy performance of the generalized space shift keying (GSSK) visible light communication (VLC) system, in this paper, an optical jamming-aided secrecy enhancement scheme is proposed, in which the source transmitter (S) simultaneously sends both the confidential desired signal and optical jamming signals under the amplitude and power constraints. The optical jamming signals obey the truncated Gaussian distribution for satisfying the constraints. Given the discrete set of channel inputs, the optical jamming-aided GSSK-VLC system's secrecy performance is analyzed. Explicitly, the average mutual information (AMI), the lower bound of AMI and its closed-form approximation as well as the achievable secrecy rate are formulated analytically. Furthermore, the optimal power sharing strategy of the proposed GSSK-VLC systems relying on optical jamming is derived. Closed-form expressions are provided for the optimal power sharing in both the low- and high-SNR regions. Finally, the extensive simulation results are presented to validate our analytical results.

In this paper, we investigate the secrecy performance of matched-filter (MF) and zero-forcing (ZF) precoding in a multiuser massive multiple-input multiple-output (MIMO) system with a multi-antenna passive eavesdropper. For the two precoding schemes, we find that the equivalent wiretap channels are similar and thus the eavesdropper achieves the approximate same sum-rate. Closed-form expressions of ergodic secrecy sum-rate (ESSR) are derived for the both schemes in the low and high signal-to-noise ratio (SNR) regimes. We show that a positive ESSR of MF scheme may be not achieved when the BS simultaneously serves more than two users with high transmit power, while the ESSR of ZF scheme always grows with the number of the served users. On the contrast, MF scheme is better than ZF scheme in the low SNR regime. Simulation results corroborate the analytic results.

This paper investigates the physical-layer security of a multiuser peer-to-peer (MUP2P) relay network for amplify-and-forward (AF) protocol, where a secure user and other unclassified users coexist with a multi-antenna eavesdropper and the eavesdropper can wiretap the confidential information in both two cooperative phases. Our goal is to optimize the transmit power of the source and the beamforming weights of the relays jointly for secrecy rate maximization subject to the minimum signal-to-interference-noise-ratio (SINR) constraint at each user, and the individual and total power constraints. Mathematically, the optimization problem is non-linear and non-convex, which does not facilitate an efficient resource allocation algorithm design. As an alternative, a null space beamforming scheme is adopted at the relays for simplifying the joint optimization and eliminating the confidential information leakage in the second cooperative phase, where the relay beamforming vector lies in the null space of the equivalent channel of the relay to eavesdropper links. Although the null space beamforming scheme simplifies the design of resource allocation algorithm, the considered problem is still non-convex and obtaining the global optimum is very difficult, if not impossible. Employing a sequential parametric convex approximation (SPCA) method, we propose an iterative algorithm to obtain an efficient solution of the non-convex problem. Besides, the proposed joint design algorithm requires a feasible starting point, we also propose a low complexity feasible initial points searching algorithm. Simulations demonstrate the validity of the proposed strategy.

This paper studies a single-input multi-output multi-eavesdropper (SIMOME) wiretap channel with multiple friendly single-antenna jammers. We consider random networks where the jammers and the eavesdroppers are distributed according to independent two-dimensional homogeneous Poisson point processes (PPP). We propose an opportunistic jammer selection scheme for the physical layer security enhancement, where the jammers whose channels are nearly orthogonal to the channel direction information (CDI) of the legitimate channel are selected to transmit independent and identically distributed (i.i.d.) Gaussian jamming signals to confound the eavesdroppers. The proposed scheme does not require a centralized design and signal coordinations among multiple jammers are not needed anymore. Furthermore, we analyze both the achievable secrecy throughput and the ergodic secrecy rate of the proposed jammer selection scheme. Based on the analysis results, we optimize the selection threshold for the secrecy throughput maximization and ergodic secrecy rate maximization. Simulation results show that the proposed jammer selection scheme can achieve a substantial performance gain.