In this paper, we propose a robust secure communication scheme for a two-Unmanned Aerial Vehicle (UAV) scenario with the assistance of Intelligent Reflecting Surface (IRS), in which one legitimate user and one eavesdropper are considered. In the proposed scheme, the information is transmitted from one UAV named information UAV to the user via the assistance of the IRS, while the jamming information is transmitted by the other UAV named jamming UAV equipped with multi-antenna to interfere with the eavesdropper and safeguard the communication between information UAV and legitimate receiver. For the considered communication system, we assume that the Channel State Information (CSI) of the eavesdropping channels are imperfect. In this imperfect CSI case, we formulate a robust non-convex optimization problem. By jointly optimizing UAV transmit power, trajectory, and IRS phase shifters, the suboptimal average secrecy rate of the proposed scheme can be obtained. Specifically, Lagrangian dual transform and quaduratic transform are introduced to convert the objective function into more tractable form; S-Procedure is used for handling CSI uncertainty; and a two-stage penalty function algorithm is applied to obtain rank-one phase shifters solution. Numerical simulation results validate some interesting insights: (1) The IRS can bring strong robustness to the two-UAV security communication system; (2) Deploying jamming UAV in the IRS-UAV security communication system can greatly improve security performance, especially employing more antennas at the jamming UAV.

Unmanned aerial vehicles (UAVs) could acquire strong line-of-sight (LoS) channels for terrestrial nodes, which means UAV communications are more vulnerable to jammers and eavesdroppers. Thanks to the reconfigurable intelligent surface (RIS), it is capable of reconfiguring the propagation environment and has good prospects for forthcoming secure transmission in combination with UAV wireless network. In this paper, we facilitate RIS to aid the uplink communication between the ground user and the UAV in the existence of a malevolent jammer and an eavesdropper by maximizing the average secrecy rate (ASR) of the proposed scheme. In order to achieve this goal, we jointly optimize the transmission power of the ground user, the RIS phase shift, and the trajectory of the UAV. Nevertheless, the proposed problem cannot be solved directly because of the coupled optimization variables and the non-convexity. Consequently, we tackle it by decomposing the original problem into three achievable sub-problems, in which formulated problem could be handled by using alternative optimization, the successive convex approximation, and semidefinite relaxation. Finally, we continuously optimize three variables and iterate over three sub-problems until the ASR converges to a stationary value. Simulation results show that the proposed scheme effectively boost the ASR compared with other baselines.

Due to the broadcasting characteristics of wireless channels, both jammers and eavesdroppers pose a serious threat to wireless communications. In this article, we propose a scheme using active reconfigurable intelligent surface (RIS) to assist secure communication and prevent simultaneous jamming and eavesdropping. In this scheme, we assume that the jammer only interferes with the legitimate user, due to the potential cooperation between the eavesdropper and the jammer. To maximize the secrecy rate, a design problem of joint optimization of base station beamforming, and amplification factor and phase shifts matrices at the active RIS is proposed. Due to the non-convexity and coupling variables of this problem, we propose to use alternating optimization and semidefinite relaxation techniques to solve this optimization problem. Simulation results show that active RIS leads to a higher system secrecy rate compared to existing schemes in the presence of both jamming and eavesdropping.

The application of Internet of Things (IoT) may suffer from serious security issue, such as the attack and wiretap from jammers and eavesdroppers, which results in the degradation of reception of useful signals at the IoT devices (users), affecting the secrecy performance for the IoT application. In this work, we propose to introduce an active simultaneously transmitting and reflecting reconfigurable intelligent surface (ASTAR-RIS) to resist jamming and eavesdropping caused by multiple jammers and eavesdroppers, respectively. For the security purpose, we formulate a sum rate maximization problem subject to the imperfect channel state information (CSI) and maximum tolerable leakage rate at the eavesdroppers. By jointly optimizing beamformers at the base station (BS) and that at the ASTAR-RIS including phase shifts and amplification factors, simulation results show that the proposed robust scheme is able to provide significant improvement as compared with other baselines.

The integration of the sixth-generation (6G) communication technology with the Internet of Things (IoT) is one of the directions in achieving a digitalized world, aiming to provide ultrahigh-speed communication services that exhibit higher energy-efficiency, lower latency, and heightened reliability and availability. In this article, we investigate the use of the simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS), one of the candidate technologies for 6G communication, along with the index modulation (IM) in multiantennas ambient backscatter communication system (ABCS) to form the STAR-RIS-assisted ABCS with spatial modulation (STAR-RIS-ABCS-SM). In particular, through the utilization of STAR-RIS and backscatter communication, we meet the demand for low-power wireless communication devices in the green communication, which is also a crucial characteristic of the IoT. Specifically, we introduce STAR-RIS into ABCS, which not only significantly boost the signal strength but also achieve full communication coverage. Meanwhile, we apply the spatial modulation (SM) technology in the multiantennas backscatter tags (BTs), located on both sides of the STAR-RIS, and use joint detection at the reader to enhance the system’s spectral efficiency (SE) as well as its bit error rate (BER) performance. Furthermore, we divide the STAR-RIS into various subsurfaces to form patterns that further enhance SE, which is termed STAR-RIS-assisted ABCS with pattern index and SM (STAR-RIS-ABCS-PISM) scheme. Finally, theoretical BER analytical expressions for both schemes are derived and presented. Simulation and theoretical results demonstrate the enhanced performance of the proposed schemes as well as the validity of the system model.

Intelligent reflecting surface (IRS) has been proposed as a promising candidate technology for next generation communication network, due to its superiority in reliable and high quality communication. In this letter, we propose a novel communication scheme that combines IRS with index modulation (IM) to achieve high spectral efficiency (SE), which is named IRS-assisted extended variable spatial modulation (IRS-EVSM). In the proposed scheme, the number of active antennas is determined by different transmission modes in each time slot, while IRS is divided into a number of sub-surfaces. To avoid the detection ambiguity at the detector, each transmission mode has its own modulation orders. Meanwhile, the theoretical upper bound of average bit error rate (ABER) based on maximum likelihood (ML) detector is proposed. Moreover, the impact of imperfect channel state information (CSI) on the system performance is investigated. Simulation results show the bit error rate (BER) performance of IRS-EVSM is better than those of IRS-RSM and IRS-RGSM schemes, and it can achieve higher SE under the same antenna setting.