Recent Advances in Electrical & Electronic Engineering - Volume 18, Issue 6, 2025

Nowadays, the communication industry is looking for a cognitive radio platform that can be used to handle multiple frequency bands, utilize various transmission protocols and be reconfigurable. For spectrum allocation, two methodologies have been adopted for CR between users who are licensed (PU) and those who are not (SU). They are spectrum overlay and spectrum underlay. Secondary users need to operate below the principal users' noise level therefore, significant restrictions resisted on the strength of their transmission in spectrum underlay methodology. Spectrum underlay is a type of underlay that is used in the construction of the unoccupied section of the spectrum searched by CR in the spectrum overlay process. A reconfigurable antenna is needed on RF front-end side of CR, which will a range of completely to span a vast array of frequencies specified sub-bands of frequency, and this is often a major design challenge. An antenna with a flexible monopole for Ultra-wideband equipment competent to function between the frequency range of 3.1 GHz to 10.6 GHz. Designs of reconfigurable antennas reported in the literature are mostly observed to be capable of manual tuning or switching between two or a few frequency bands. Hence, the requirement of new designs of integrated UWB and reconfigurable narrowband antennas that operate from 2 GHz and up to 12 GHz frequency range with a high degree of automated tunability or switching facility into different narrow bands would have a strong application potential for CRs.

The use of computationally intensive applications requiring substantial storage resources in vehicular adhoc networks is on the rise due to the technology shift from smart, intelligent vehicles to autonomous vehicles. Cloud computing addresses this problem to some extent by providing computational and storage facilities for the significant amount of data generated by vehicular nodes. However, it still cannot meet the stringent requirements of highly dynamic vehicular nodes in a real-time environment. The delay-sensitive applications of vehicular ad hoc networks instill the need for computing facilities in the closest possible proximity to the vehicular nodes. Therefore, fog computing has found potential in vehicular ad hoc network applications. Fog computing brings storage and computing resources closer to vehicles. Fog-based vehicular ad hoc networks can help improve the issues of first-generation vehicular ad hoc networks, such as latency, location perception, and concurrent response. Based on existing research, using fog computing decreased the delay by 50-60% and 60-70% in vehicular ad hoc network safety and entertainment and commercial applications, respectively, compared to cloud computing. An extensive study of the amalgamation of fog computing and vehicular ad hoc networks should be conducted to understand the underlying challenges of fog-based vehicular ad hoc networks. Existing surveys only include specific applications of this technology. However, we present an extensive survey focusing on the architecture of these two technologies, their integration, use cases of fog vehicular ad hoc networks, simulation tools, important performance metrics, the challenges in multiple contexts, and the gaps that need to be addressed, as well as suggest prominent journals in this field. This paper will not only impart knowledge to researchers in this area but also provide them with insights to identify the challenges and pursue their work further in fog-based vehicular ad hoc networks.

This paper delves into the potential of Fault Current Limiters (FCLs) as a transformative technology within power systems. FCLs assume a pivotal role in streamlining network expansion efforts, sustaining fault current levels, and augmenting the overall performance of power systems. The classification of FCLs is outlined, encompassing superconducting FCLs (SFCLs), Solid-State FCLs (SFCLs), and non-superconducting FCLs (Non-SFCLs). The core of this study lies in an exhaustive review of relevant literature, with a keen focus on optimal allocation strategies for FCLs. The primary objective of this paper is to function as an all-encompassing reference for both researchers and engineers, providing optimal FCL allocation studies. This paper discusses various techniques for the optimal allocation of FCLs within power systems. These allocation methods are categorized based on multiobjective functions such as cost, fault current reduction, stability, protection coordination, reliability, and power quality. This search presents an overview of the FCL survey structured around key components, including objective functions, design variables, constraints, optimization methods, network types, FCL types, and research contributions. This work aims to empower professionals in the field with a robust understanding of FCL allocation, ultimately contributing to the efficient and sustainable evolution of power systems. FCLs represent a promising technology for enhancing the performance and reliability of power systems, and this paper serves as a comprehensive resource for those interested in optimizing their allocation within these systems.

Recently, many researchers have studied its performance within Mobile Ad-hoc Networks (MANETs). Every ad hoc network protocol focuses on a different set of measurements and traits. The majority of the currently utilized mobility models are employed to provide realistic movement patterns for MANET scenarios. A crucial element in the creation of MANET protocols is simulation. The future topology of a network can be predicted, which enables Quality of service-aware routing to choose a dependable link for data transmission. Ant algorithms, also known as swarm intelligence, are a wider field of study that deals with algorithmic approaches that are motivated by the behaviour of ant colonies and other insects. Ant Colony Optimization (ACO) is a subset of this larger topic. Based on the pheromone value deposited over the link, we identified two categories for the link quality in the proposed approach. We have demonstrated how the network's performance is enhanced by the suggested technique. The nodes are moving in the specified terrain dimensions through the Enhanced Manhattan Mobility Model (EMMM). The five QoS performance metrics are analyzed over three MANET routing protocols. The comparison is made over two important factors-mobility and pause time with the proposed ACO technique of reliable links. In the first experiment of different speeds, DSR is 25.5% better than AODV and 5.3% better than DSDVin metric packet dropping, 1.15% better than AODV and 1.01% better than DSDV in Packet Delivery Ratio, 1.5% better than AODV and 1.04% better than DSDV in packet overhead, and 62.7% better than AODV and 73.1% better than DSDV in average end-to-end delay. In the second experiment of pause times, DSR is 25.05% better than AODV and 4.5% better than DSDV in packet dropping, 1.18% better than AODV and 1.01% better than DSDV in packet delivery ratio, 1.01% better than DSDV in throughput, 0 to 0.002% in packet overhead, and 0.02% to 0.005% shorter delay.

Switched Reluctance Motors (SRMs) are renowned for their robustness, wide speed range, and high fault-tolerant capability, making them highly suitable for high-speed and safety-critical applications. Research has indicated that power converters are particularly susceptible to failure in switched reluctance motor drive systems (SRD). Open-circuit faults in the power converter or winding can result in phase-deficient operation, leading to decreased output torque and significant torque ripple in SRMs. On the other hand, a short-circuit fault in the power converter can cause a substantial increase in circuit current, potentially generating a large reverse braking torque that can destabilize the drive system and damage the entire system, thereby impacting the normal operation of the SRD. Consequently, it is imperative to conduct fault diagnosis and fault tolerance studies on power converters for SRD. In this article, the fault diagnosis of a switched reluctance motor power converter is summarised and described in four aspects, namely current detection methods, gate signals auxiliary, and mathematical analysis. Fault tolerance of switched reluctance motor is summarised and described in two aspects, namely improvement of power converter topology, fault tolerance, and control strategy. A new switched reluctance motor fault-tolerant power converter structure is proposed.