Van Phu Tuan

Intelligent reflecting surface has recently emerged as a cost-effective solution to overcome the deep fading and uncontrollable wireless environment. This leads to a need for studies on the wireless channels of IRS-aided wireless communication (IRSaWC). This paper proposes a novel channel modelling method for the IRSaWC by exploiting the physics characteristic of the electromagnetic (EM) field on the IRS and the modified Saleh-Valenzuela (SV) model. Firstly, the reflection on a single reflecting tile (RT) of the IRS is investigated in the presence of a misalignment between the RT’s configured incident angle and the actual incident angle, and the RT’s phase distortion. Then, the path loss and phase shift models for the reflected field are developed. Extending our study to the multiple-RT scenario and utilizing the modified SV model, the channel characteristic for the IRSaWC is determined. Our analysis shows that the information signal at the receiver experiences a Rice fading with controllable parameters. Theoretical results for the path loss, the channel’s parameters, and the received distortion power are derived; moreover, an approximate distribution for the combined signal-to-noise ratio (SNR) for IRS-aided multiple-antenna wireless systems (IRSaMAWSs) has been investigated with the aim of conducting further studies on theoretical performance for IRSaMAWSs.

This paper studies the effectiveness of intelligent reflecting surface (IRS) in enabling robust secure communications for indoor non-orthogonal multiple access (NOMA) systems. Using an IRS-control and power-allocation (PA) strategy (IRSCaPAS), the system purposely allocates its reflecting tiles (RTs) with reasonable phase shifts to the receivers, including two users and a potential eavesdropper, as well as adjusts the PA factor of NOMA. The goal of the paper is to boost the average secrecy rates (ASRs) for the users via optimizing the IRSCaPAS. The closed-form expressions for the ASR are derived for the generalized case where the successive interference cancellation (SIC) receivers for NOMA are imperfect. Using these expressions, heuristic algorithms (HA) are designed to optimize the IRSCaPAS. Numerical results show a vital role of the IRS in enhancing the system secrecy performance and the efficiency of the proposed algorithms. Moreover, these results provide useful insights into the effects of various key parameters on the secrecy performance, such as the size of the IRS, the transmit power, the NOMA PA factors, the scattering-signal power, the $K$ factors of the Rice channels, the SIC imperfection factor, and the locations of devices.

This paper studies the secrecy performance of an intelligent reflecting surface (IRS)-aided indoor wireless communication where the IRS is capable of adjusting the direction and phase shift of reflected signal on its surface and assists a source to communicate with an authenticated user in the presence of several unauthenticated users, which can be potential eavesdroppers. The goal of this paper is to design a tile-allocation-and-phase-shift-adjustment (TAaPSA) strategy for the IRS to optimize the average secrecy rate (ASR); moreover, the respective secrecy outage probability (SOP) for this TAaPSA is evaluated. To achieve this goal, the ray model and the Rice distribution are adopted to describe the propagation of the IRS’s reflected signals and the fading process, respectively. Closed-form analytical expressions for the ASR and the SOP are derived. Using these analytical results, a genetic algorithm (GA) is utilized to find an optimal TAaPSA strategy for the IRS. The accuracy of the analytical results and the improvement in ASR using GA-based TAaPSA strategy are verified by simulation results.

This paper studies the secure communication of a non-orthogonal multiple-access (NOMA) relaying system in the presence of an eavesdropper in which the NOMA communication between a source and two users is assisted by an energy-harvesting (EH) relay. The relay extracts a part of its received signal strength using a power-splitting (PS) policy then harvests energy using a non-linear EH (NLEH) circuit. A friendly jammer sends jamming signals to help secure communication. The jammer is exploited as an additional energy source. A store-and-transmit (SaT) scheme which allows the EH relay to perform energy storing and information transmitting is proposed. For performance evaluation, the closed-form expressions for three metrics, secrecy outage probability (SOP), average achievable secrecy rate (AASR) and average stored energy (ASE) are derived. These results enable studies on the effects of various system parameters, such as NOMA power-allocation factors, target secrecy rates, jammer’s location, and relay’s power levels, on the system performance.

In this paper, we investigate the secrecy outage performance of the Non-orthogonal Multiple Access system (NOMA) in an untrusted relaying energy harvesting (UEH) network with the multiple-input multiple output (MIMO) architecture using the transmit antenna selection/ maximal ratio combining (MRC) techniques. In proposed network, the source communicates with users under the help of multiple UEH network using the power-splitting (PS). In addition, to improve the secrecy outage performance and protect the confidential source signal from the untrusted relaying network, the source works as the jammer with the role generating the artificial noise (AN). For the evaluation of secrecy performance of each user we derive the closed- form expressions of the secrecy outage probability (SOP) over Rayleigh fading. Moreover, comparisons between MIMO/NOMA and MIMO/OMA systems and the effects of various system parameters are examined. The accuracy of analytical results is verified by Monte Carlo simulations.

In this paper, we investigate the secure capacity of a cooperative energy-harvesting communication via an amplify-and-forward (AF) untrusted relay, which can be a potential eavesdropper, in the presences of multiple external eavesdroppers. The eavesdropper network chooses an eavesdropper which possesses the highest source-eavesdropper channel gain for overhearing the source’s confidential signal. To degrade the signal quality at the untrusted relay and the best eavesdropper while maintaining signal quality at the destination, the destination sends artificial noise (AN) during the communication. Both the source signal and AN can be exploited as energy sources. We derive the analytical expression for the average secrecy capacity (ASC) for evaluating the secure capacity. The accuracy of analytical results is verified by Monte Carlo simulations.