Intelligent reflecting surfaces (IRSs) are anticipated to provide reconfigurable propagation environment for next generation communication systems. In this paper, we investigate a downlink IRS-aided multi-carrier (MC) non-orthogonal multiple access (NOMA) system, where the IRS is deployed to especially assist the blocked users to establish communication with the base station (BS). To maximize the system sum rate under network quality-of-service (QoS), rate fairness and successive interference cancellation (SIC) constraints, we formulate a problem for joint optimization of IRS elements, sub-channel assignment and power allocation. The formulated problem is mixed non-convex. Therefore, a novel three stage algorithm is proposed for the optimization of IRS elements, sub-channel assignment and power allocation. First, the IRS elements are optimized using the bisection method based iterative algorithm. Then, the sub-channel assignment problem is solved using one-to-one stable matching algorithm. Finally, the power allocation problem is solved under the given sub-channel and optimal number of IRS elements using Lagrangian dual-decomposition method based on Lagrangian multipliers. Moreover, in an effort to demonstrate the low-complexity of the proposed resource allocation scheme, we provide the complexity analysis of the proposed algorithms. The simulated results illustrate the various factors that impact the optimal number of IRS elements and the superiority of the proposed resource allocation approach in terms of network sum rate and user fairness. Furthermore, we analyse the proposed approach against a new performance metric called computational efficiency (CE).

This work proposes a hybrid intelligent Deep Learning (DL)-enabled mechanism to secure IIoT infrastructure from lethal and sophisticated multi-variant botnet attacks. The proposed mechanism has been rigorously evaluated with latest available dataset, standard and extended performance evaluation metrics, and current DL benchmark algorithms. Besides, cross validation of our results are also performed to clearly show overall performance.

Time-modulated arrays (TMAs) have been found useful to construct directional modulation (DM) transmitters, offering physical-layer security. Two issues, however, exist in conventional TMA DM, which are high power loss and generation of mirror harmonic frequency signals that may compromise wireless security. In this letter, we propose to construct DM transmitters using a high efficiency TMA. By carefully designing the time sequences of the selected phase shifters, the DM symbols modulated upon multicarrier can be synthesized with suppressed mirror harmonic frequencies. It is shown that the proposed TMA DM transmitters here enjoy feeding network efficiency of 100%, and the transmit DM symbols can be synthesized at a pre-selected frequency only, significantly enhancing security performance. The effectiveness of the proposed scheme is validated via bit error rate (BER) simulations. Meanwhile, The TMA DM also can be used as a potential technique for the integrated sensing and communication (ISAC).