The explosive popularity of small-cell and Internet of Everything devices has tremendously increased traffic loads. This increase has revolutionised the current network into 5G technology, which demands increased capacity, high data rate and ultra-low latency. Two of the research focus areas for meeting these demands are exploring the spectrum resource and maximising the utilisation of its bands. However, the scarcity of the spectrum resource creates a serious challenge in achieving an efficient management scheme. This work aims to conduct an in-depth survey on recent spectrum sharing (SS) technologies towards 5G development and recent 5G-enabling technologies. SS techniques are classified, and SS surveys and related studies on SS techniques relevant to 5G networks are reviewed. The surveys and studies are categorised into one of the main SS techniques on the basis of network architecture, spectrum allocation behaviour and spectrum access method. Moreover, a detailed survey on cognitive radio (CR) technology in SS related to 5G implementation is performed. For a complete survey, discussions are conducted on the issues and challenges in the current implementation of SS and CR, and the means to support efficient 5G advancement are provided.

Traditional electrical power grids are transitioning from centralised operation with unidirectional energy and information flows (from the generation domain to customers) to smart grids with decentralised mode of operation and bidirectional flows. This reversal of traditional power flow direction is due to the connections of active loads such as distributed energy resources (DERs) and renewable energy sources close to the distribution network. Through advanced and sophisticated information and communication technologies (ICTs), efficient DER management and various applications for reliable and secure power delivery are enabled. However, before the adoption of any ICT solution in the grid, several challenges remain, which include interoperability, security and privacy concerns, and the ever-increasing demands to support various services and applications. Although the information within the grid is becoming more visible because of bidirectional communication flow, this only applies to transmission networks and not active distribution networks, which house numerous smart grid applications. There is also little research that supports the automatic operation of active distribution networks. Hence, this article explores and reviews active distribution network communication technologies, as well as the applications and communication standards. This review paper also highlights issues and challenges with active distribution networks and opportunities and research trends in the distribution domain from an ICT perspective.

A smart grid provides a bidirectional flow of electricity and information whilst ensuring well-balanced electricity supply and demand. The key enabler for the smart grid is its robust communication infrastructure. Choosing the best communication technology for the smart grid is crucial as it involves a mixture of critical and non-critical traffic. This study provides a comprehensive review on smart grid communication and its possible solutions for a reliable two-way communication toward supporting diversified power grid applications. Existing networking methods along with their advantages and weaknesses are highlighted for future research directions. The communication network architecture in the smart grid, with details on each networking technology, switching methods and medium for data communication, is critically reviewed to identify the existing research gaps. A discussion on issues and challenges encountered in smart grid communication for current implementation is highlighted together with the recommendations for further improvement. Overall, the highlighted issues and recommendations from this study are useful to researchers, technology providers and industries to develop new communication technologies for the smart grid that will provide reliable, robust, and suitable two-way communication in the future.

Multi Criteria Decision Making (MCDM) helps decision makers (DMs) solve highly complex problems. Accordingly, MCDM has been widely used by DMs from various fields as an effective and reliable tool for solving various problems, such as in site and supplier selection, ranking and assessment. This work presents an in-depth survey of past and recent MCDM techniques cited in the literature. These techniques are mainly categorised into pairwise comparison, outranking and distance-based approaches. Some well-known MCDM methods include the Analytical Hierarchy Process (AHP), Analytical Network Process (ANP), Elimination et Choix Traduisant la Realité (ELECTRE), Preference Ranking Organization METHod for Enrichment of Evaluations (PROMETHEE), Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR). Each of these methods is unique and has been used in a vast field of interest to support DMs in solving complex problems. For a complete survey, discussions related to previous issues and challenges and the current implementation of MCDM are also presented.

Communication networks are expanding rapidly and becoming increasingly complex. As a consequence, the conventional rule-based algorithms or protocols may no longer perform at their best efficiencies in these networks. Machine learning (ML) has recently been applied to solve complex problems in many fields, including finance, health care, and business. ML algorithms can offer computational models that can solve complex communication network problems and consequently improve performance. This paper reviews the recent trends in the application of ML models in communication networks for prediction, intrusion detection, route and path assignment, Quality of Service improvement, and resource management. A review of the recent literature reveals extensive opportunities for researchers to exploit the advantages of ML in solving complex performance issues in a network, especially with the advancement of software-defined networks and 5G.