Visible light communication (VLC) with energy harvesting (EH) has emerged as a promising enabler for sustainable, batteryless, and autonomous Internet of Things (IoT) networks. By leveraging the dual role of optical signals for communication and power transfer, EH-VLC links can significantly enhance the energy efficiency and lifetime of autonomous, low power IoT deployments. In this work, we consider a line-of-sight (LoS) simultaneous lightwave information and power transfer (SLIPT)-enabled EH-VLC system. For it, we analyze energy-centric performance measures useful for autonomous optical EH-IoT deployments. Specifically, we derive closed form expressions for the bounds of the amount of fading (AoF) and for the fading statistics-averaged energy efficiency (FSAEE). To gain additional insights, we derive an upper bound for the energy harvested outage probability (EHOP). Throughout the performance analysis, we assume two different turbulence effects, modeled by Gamma-Gamma and log-normal (Gaussian in the log domain) fading. The closed form analytical expressions are validated through simulations and benchmark comparisons, and the analysis is further extended to anL-branch diversity receiver, which significantly reduces the EHOP while improving link robustness. The performance analysis and simulation results provide valuable design directions for the deployment of SLIPT-enabled, EH-VLC-based next generation sustainable IoT networks.

With exponential growth and associated milestones set in quantum information and quantum computing (QC) technologies, QC is becoming a threat to existing key encryption strategies that leverage asymmetric cryptographic algorithms like RSA (Rivest, Shamir, Adleman) encryption. Since these algorithms form the backbone of Internet communication, it becomes essential to utilize secure quantum methods for key generation and distribution. The quantum key distribution (QKD) networks have since been extensively researched and implemented with various communication protocols, primarily utilizing the Quantum Entanglement and Quantum Key Correction paradigms. Efficient routing is one of the significant problems in classical and hybrid networks. It is important to propose novel hybrid and efficient routing protocols based on modern optimization approaches to design secure, fidelitous, and efficient quantum information networks. We perform this optimization by generating a cost function to implement quantum optimization algorithms, namely the Quantum Approximate Optimization Algorithm (QAOA). We further draw a comparison with the state-of-the-art graph theory-based optimization techniques. The primary objective of this paper is to fabricate a robust quantum communication network and to subsequently analyze the effectiveness of quantum based techniques to carry out network routing and link optimization, generating scope for the utilization of quantum architecture to enhance security in Q KD networks.

We consider a two-hop, hybrid collaborative radio communication system having regenerative and non-regenerative energy harvesting (EH) relays. The regenerative or non-regenerative relay harvests energy from its received radio frequency (RF) signals transmitted by the collaborative EH radio system's source node. We employ simultaneous wireless information and power transfer (SWIPT) with the time-switching EH protocol. We propose an insightful hybrid cooperative relaying protocol and its performance analysis. Specifically, we formulate an ergodic capacity optimization problem with average power constraint on relay transmissions. The proposed hybrid relaying protocol analysis and numerical results provide valuable insights into the effect of various hybrid EH collaborative radio system parameters. These parameters include EH time and non-regenerative relay's amplification factor on system performance in terms of normalized capacity. Furthermore, a comparison between multiple relaying protocols shows that hybrid relaying provides better fading-averaged capacity performance.

Abstract In this work, the authors consider a two‐hop cooperative radio communication system that consists of energy harvesting relays. The EH relays harvest energy from its received radio frequency signal. The EH relay nodes adopt the time‐switching protocol for simultaneous EH and information processing. For the system model, the authors propose an energy‐efficient, outage‐constrained relaying policy. In it, the EH relay that harvests maximum energy forwards the information to the destination. However, the selected EH relay transmissions are outage‐constrained. For the proposed outage‐constrained collaborative EH system model, the authors present insightful analysis. Specifically, the authors derive a single integral expression for the expectation of maximum energy harvested over frequency‐flat Rayleigh fading and shadowing channel. The authors also present an insightful link outage probability analysis and asymptotic analysis in a useful scaling regime. Besides outage analysis, the authors investigate the proposed policy's performance in terms of average spectral efficiency and average energy efficiency. To validate the analytical results, the authors conduct numerical simulations. Using the numerical plots, the authors quantify the proposed policy's link outage and energy efficiency performance gains compared with benchmark policies. The proposed outage‐constrained, green cooperative communication policy and its analysis are useful for green collaborative EH systems.

In this paper, the author investigates the positioning outage probability performance of navigation satellite link. For the analysis, the author considers the satellite downlink wherein the user has a mobile navigation receiver. The author presents an insightful analysis which comprises of analytical results for positioning outage probability (POP). Specifically, the author derives tractable expressions for POP as functions of link parameters in various fading scenarios, namely, small scale Rayleigh fading, Rician fading, Shadow fading, and combined Rician and shadow fading. To numerically evaluate the POP performance of the derived analytical results, the author plots the POP for various simulation parameters. From the numerical plots, the author observes that the POP improves as the average signal power to interference plus noise power ratio (SINR) and bandwidth. However, this dependence on model parameters is not the same for all the fading scenarios. Finally, the author suggests multi-antenna receive diversity and combining technique to improve POP performance.

Free space optical (FSO) inter‐satellite links could often be non‐reliable due to the imperfect line of sight (LOS) links. To achieve more reliable communication, the authors propose hybrid inter‐satellite links. However, this leads to new challenges like switching physical (PHY) layers at the satellite's transmitter. In this work, they propose a novel hybrid radio frequency‐FSO (RF/FSO) satellite system. For it, they develop a novel best beam selection policy (BBSP) and switching of FSO and RF to improve the reliability of the inter‐satellite links. To obtain more insights, they investigate the performance of BBSP by deriving expressions for the outage probability, average spectral efficiency, and average bit error rate of the BBSP. For the PHY switching, they compare the instantaneous error probabilities of RF and FSO links and find the signal‐to‐noise ratio threshold at which it is more efficient to switch to RF. They further improve this threshold by considering a satellite transmitting multiple beams and choosing the best source beam. To validate the analytical findings, they simulate the proposed model with CubeSat level parameters. They and that the BBSP delivers superior performance in terms of various performance measures, which shows its applicability in next‐generation satellite systems.

Cooperative device‐to‐device (D2D) wireless systems use relays such as amplify‐and‐forward (AaF) and decode‐and‐forward (DaF). The AaF relay is simple to implement but amplifies noise as well. Conventional DaF relay does decoding and acts as a regenerative relay, hence deliver better noise performance. In this study, the authors generalise the cooperative D2D model by designing power adaptive decode‐and‐forward relays. In it, the probabilistically selected relay subject to an average relay transmit power constraint does decoding and jointly adapt its gain and transmit power as a function of the channel gains to the destination link. For the proposed cooperative D2D system model, the authors derive the optimal relaying policies which set relay gains to (i) minimise the fading averaged symbol error rate; (ii) maximise fading averaged spectral efficiency and (iii) maximise fading averaged energy efficiency. Then they present a comprehensive performance analysis of the optimal policies. The mathematical analysis includes derivations of exact expressions and their upper bound expressions. To further extend the FAvSER analysis, they investigate diversity order in an insightful scaling regime. Then they present extensive numerical results to validate the derived analytical expressions and to show that the proposed optimal relaying policies outperform the benchmark policies.

The author consider a relay‐assisted, two hop, cooperative device‐to‐device (D2D) communication system where a source device S transmits data to a destination device D using a non‐regenerative cooperative relay whose average transmit power is constrained. For the cooperative D2D system, the author consider the problem of optimally adapting the relay gain as a function of fading gains of S – R and R – D links to maximise fading‐averaged spectral efficiency. The author derive the spectral efficiency‐optimal relay gain adaptation policy (SERGAP), which determines optimal gain for the relay, and, analyse the fading‐averaged spectral efficiency of SERGAP. To gain more insights, the author derive upper bounds on the average spectral efficiency, and, also investigate its asymptotic behaviour using an insightful analysis. Furthermore, the author extend the fading‐averaged analysis to a system having multiple relays. The author also present numerical results for single relay and multiple relay systems and benchmark the proposed policy's performance with conventional and suboptimal relaying policies. The author show that SERGAP delivers higher average spectral efficiency than conventional relaying policies. Finally, spectral efficiency‐optimal relay placement for the proposed policy is also investigated via simulations, and, the author find that it is different from the suboptimal relaying policies.