The spectral efficiency of sixth-generation (6G) wireless networks is anticipated to experience large improvements through the implementation of non-orthogonal multiple access (NOMA) technology. The integration of short-packet communications (SPC) into NOMA networks enables low-latency operation and high spectral efficiency. The present study investigates the performance of multiple users in a NOMA downlink SPC system operating over an$\alpha - \kappa - \mu$shadowed fading channel. Precise and asymptotic closed-form approximations for the average block error rate (BLER), reliability, throughput, goodput, and overall BLER were derived using approximate Gaussian-Chebyshev quadrature. The analytical results were validated through numerical simulations, providing insights into the impact of fading parameters on system performance. The study's findings indicate that the proposed downlink NOMA SPC system is highly suitable for ultra-reliable and low-latency communications (URLLC), achieving reliability levels of 99.99% for multiple users. The study also determined the optimal transmission bit rate required to maximize throughput and goodput while minimizing the BLER. The proposed downlink NOMA SPC system operating with an$\alpha - \kappa - \mu$shadowed fading channel demonstrates high potential for improving Internet of Things (IoT) network performance over conventional downlink orthogonal multiple access (OMA) approaches. Most of the analysis adopts perfect successive interference cancellation (pSIC) and perfect channel state information (pCSI) as theoretical benchmarks, while additional results explicitly quantify the performance degradation caused by residual interference and channel estimation errors (CEE). The results reveal that imperfect SIC (ipSIC) dominates the BLER floor at high signal-to-noise ratio (SNR), whereas imperfect CSI (ipCSI) primarily affects the moderate-SNR regime, highlighting distinct impairment-driven performance bottlenecks. Therefore, we have extended the study by including two additional scenarios: pCSI combined with ipSIC, and ipCSI combined with ipSIC. This extension allows us to compare the performance of these systems and clearly shows that the system with pSIC and pCSI achieves the best performance. Finally, the results were validated with Monte Carlo simulations.

This article investigates the combination of active reconfigurable intelligent surfaces (aRISs) with cognitive radio networks (CRns) enabled by nonorthogonal multiple access (NOMA) to enhance the capability of aRIS-based Internet of Things (IoT) systems. The proposed system model enhances overall performance and energy allocation by combining aRIS and NOMA. In this proposed system paradigm, the secondary source (SS) controls the information transmission to two secondary users (SUs) via the aRIS element. Transmission power limitations are put in place to lessen the impression that base stations are interfering with the main purpose. This article evaluates critical system performance indicators, such as outage probability (OP), achievable ergodic rate (AER), throughput, and energy efficiency (EE). Specifically, the impact of the distance between the aRIS unit and the base station on AER is explored. The examination of the correlation among SS-aRIS-Users in the presence of the Nakagami-m fading scenario is further investigated. Such discoveries offer significant perspectives for the enhancement and configuration of aRIS-NOMA frameworks in CRn, contributing to the advancement of adaptable communication infrastructures. In contrast to the traditional method that uses orthogonal multiple access (OMA), the aRIS-NOMA system proposed in CRn appears to be a promising way to improve the performance of IoT networks based on aRIS. Simulations have demonstrated significant improvements in spectral efficiency, with gains as high as 10%–20% observed. This suggests that performance has significantly improved, particularly for OP and AER. Finally, the Monte Carlo simulation confirms and strengthens these findings.

This study investigates a two-way relaying non-orthogonal multiple access (TWR-NOMA) enabled Internet-of-Things (IoT) network, in which two NOMA users communicate via an IoT access point (IAP) relay using a decode-and-forward (DF) protocol. A power beacon (PB) is used to power the IAP to address the IAP's limited lifetime due to energy constraints. Since co-channel interference (CCI) is inevitable in IoT systems, this effect is also studied in the proposed system to improve practicality. Based on the proposed system model, the closed-form equations for the exact and asymptotic outage probability (OP) and ergodic data (ED) of the NOMA users' signals are first derived to describe the performance of TWR-NOMA systems. The system's diversity order and throughput are then evaluated according to the derived results. To further improve the system's performance, a low-complexity strategy 2D golden section search (GSS) is performed, subject to power allocation (PA) and time-switching (TS) factors, to optimize the outage performance. Finally, a deep learning design with minimal computing complexity and precision OP prediction is established for a real-time IoT network configuration. The numerical results are discussed and analyzed in terms of the effects of the CCI, the TS ratio, the PA factor, the fading parameter on the OP, system throughput, and ED.

Radio-frequency (RF) energy harvesting (EH) in wireless relaying networks has attracted considerable recent interest, especially for supplying energy to relay nodes in the Internet of Things (IoT) systems to assist the information exchange between a source and a destination. Moreover, limited hardware, computational resources, and energy availability of IoT devices have raised various security challenges. To this end, physical-layer security (PLS) has been proposed as an effective alternative to cryptographic methods for providing information security. In this study, we propose a PLS approach for simultaneous wireless information and power transfer (SWIPT)-based half-duplex (HD) amplify-and-forward (AF) relaying systems in the presence of an eavesdropper. Furthermore, we take into account both static power splitting relaying (SPSR) and dynamic power splitting relaying (DPSR) to thoroughly investigate the benefits of each one. To further enhance secure communication, we consider multiple friendly jammers to help prevent wiretapping attacks from the eavesdropper. More specifically, we provide a reliability and security analysis by deriving closed-form expressions of outage probability (OP) and intercept probability (IP), respectively, for both the SPSR and DPSR schemes. Then, simulations are also performed to validate our analysis and the effectiveness of the proposed schemes. Specifically, numerical results illustrate the nontrivial tradeoff between reliability and security of the proposed system. In addition, we conclude from the simulation results that the proposed DPSR scheme outperforms the SPSR-based scheme in terms of OP and IP under the influences of different parameters on system performance.

Mobile-edge computing (MEC) has emerged as a prominent technology to overcome sudden demands on computation-intensive applications of the Internet of Things (IoT) with finite processing capabilities. Nevertheless, the limited energy resources also seriously hinder IoT devices from offloading tasks that consume high power in active RF communications. Despite the development of energy harvesting (EH) techniques, the harvested energy from surrounding environments could be inadequate for power-hungry tasks. Fortunately, backscatter communications (Backcom) is an intriguing technology to narrow the gap between the power needed for communication and harvested power. Motivated by these considerations, this article investigates a backscatter-assisted data offloading in OFDMA-based wireless-powered (WP) MEC for IoT systems. Specifically, we aim at maximizing the sum computation rate by jointly optimizing the transmit power at the gateway (GW), backscatter coefficient, time-splitting (TS) ratio, and binary decision-making matrices. This problem is challenging to solve due to its nonconvexity. To find solutions, we first simplify the problem by determining the optimal values of transmit power of the GW and backscatter coefficient. Then, the original problem is decomposed into two subproblems, namely, TS ratio optimization with given offloading decision matrices and offloading decision optimization with given TS ratio. Especially, a closed-form expression for the TS ratio is obtained which greatly enhances the CPU execution time. Based on the solutions of the two subproblems, an efficient algorithm, termed the fast-efficient algorithm (FEA), is proposed by leveraging the block coordinate descent method. Then, it is compared with exhaustive search (ES), the bisection-based algorithm (BA), edge computing (EC), and local computing (LC) used as reference methods. As a result, the FEA is the best solution which results in a near-globally-optimal solution at a much lower complexity as compared to benchmark schemes. For instance, the CPU execution time of FEA is about 0.029 s in a 50-user network, which is tailored for ultralow latency applications of IoT networks.

In this paper, we evaluate and compare performance of multi-hop relaying (MR) protocols under impact of hardware impairments, in terms of outage probability (OP) and throughput (TP). By applying non-orthogonal multiple access (NOMA) technique at each hop, the end-to-end data rate/throughput of the MR protocol can be enhanced, as compared with the conventional one. Particularly, the transmitter at each hop combines two signals, and forwards the combined signal to the receiver which uses successive interference cancelation (SIC) to extract the data. For performance evaluation and comparison, we derive exact closed-form expressions of OP and TP for the considered protocols over Nakagami-m channel. Monte Carlo simulations are then performed to verify the theoretical derivations.

In this paper, we derived the analytical expressions of the system performance (in term outage probability and throughput) of the power splitting half-duplex power beacon-assisted energy harvesting relay network in both amplify-and-forward and decode-and-forward modes. Moreover, the analytical results are also demonstrated and convinced by using Monte-Carlo simulation. The numerical results demonstrated and convinced the analytical and the simulation results are matched well with each other in connection with all possible system parameters.

Thanks to the benefits of deploying non-orthogonal multiple access (NOMA) in wireless communications, i.e, wireless sensor networks, we evaluate an energy harvesting wireless sensor network (EH-WSN) deploying NOMA, where the destination can receive two data symbols the whole transmission process with two time slots. To be more clear, we derive expressions for the achievable data rate and outage probability. In addition, we present Monte-Carlo simulations to prove the performance and the correctness of the obtained numerical results.

The energy harvesting amplify-and-forward full-duplex relaying network over the dissimilar fading environments in imperfect CSI condition is investigated. In this system model, the energy, and information are transferred from the source to the relay nodes by the power splitting protocol with helping of the full-duplex relay node. Firstly, the outage probability, achievable throughput, and the optimal power splitting factor in terms of the analytical mathematical expressions were proposed, analyzed, and demonstrated. Furthermore, the system performance of the proposed model on the connection with all system parameters is rigorously studied. Finally, the numerical results demonstrated and convinced one that the analytical and the simulation results are matched well with each other for all system parameter values using Monte-Carlo simulation. The results show that the system performance degrades significantly but is still in a permissible interval while the channel estimation error increases and the system performance of the mixing scenarios is better in comparison with the Rayleigh-Rayleigh scenario.