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Radio resource management (RRM) for future fifth-generation (5G) heterogeneous networks (HetNets) has emerged as a critical area due to the increased density of small-cell networks and radio access technologies. Recent research has mostly concentrated on resource management, including spectrum utilization and interference mitigation, but the complexities of these resources have been given little attention. This paper provides an overview of the issues arising from future 5G systems and highlights their importance. The different approaches used in recently published surveys categorizing RRM schemes are discussed, and the survey method is presented. We report on a survey of HetNet RRM schemes that have been studied recently, with a focus on the joint optimization of radio resource allocation with other mechanisms. These RRM schemes were subcategorized according to their optimization metrics and qualitatively analyzed and compared. An analysis of the complexity of RRM schemes in terms of implementation and computation is presented. Several potential scopes of research for future RRM in 5G HetNets are also identified.

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In mobile ad hoc networks, limited energy resources and traffic congestion at the nodes are crucial issues due to the nodes being battery operated and flooding the network with packets, respectively. These issues degrade network routing performance in terms of quality of service. In this study, we proposed a contention window and residual battery-aware multipath routing scheme to enhance network performance. Our proposed routing scheme has successfully diverted the traffic load from a low energy node to a high energy node while also controlling congestion among intermediate nodes. A multi-criteria decision-making technique was also used for the selection criteria of an intermediate node in the optimal path, based on the mobility and window size contention of nodes. Eventually, the contention window and residual battery-aware multipath routing scheme has enhanced throughput, attenuated the packet loss ratio, and reduced the energy consumption in comparison to a conventional multipath optimized link state routing protocol routing scheme.

Common power system restoration planning strategy is based on a 'build up' approach, where a blackout system is sectionalized among several islands for parallel restoration prior to resynchronization. In order to speed up the resynchronization of the islands, each island must have similar energizing times. However, there is a huge number of possible combinations of islands that can be formed. Thus, this paper proposes a method to determine optimal islands that have similar energizing times. The method involves identifying transmission lines that should not be connected to form the islands. The proposed method is based on the combination of heuristic and discrete optimization methods. The heuristic technique is proposed to find initial solution that is close to the optimal solution. This solution will guide the optimization technique, which is the discrete Artificial Bee Colony optimization method, to find the optimum solution. The proposed method also considers restoration constraints including black start generator availability, load-generation balance, and the maintenance of acceptable voltage magnitude within each island. The proposed method is validated via simulation using IEEE 39, 118-bus and 89-bus European systems. The advantage of the proposed method in terms of restoration time is demonstrated through a comparison with other literature.

A multibeam array antenna employing a Butler matrix is a promising solution for fifth generation (5G) base stations. Due to inaccurate phase differences between output ports in the Butler matrix, the radiation characteristics could show incorrect main beam directions. In addition, the literature has also reported the issue of high amplitude imbalance in the Butler matrix. This paper presents a single-layer multibeam array antenna fed by an 8 × 8 Butler matrix operating at 28 GHz for 5G base station applications-a more cost-effective solution for large-scale production.The Butler matrix consists of twelve quadrature hybrids, sixteen crossovers, and eight phase shifters. This circuit was integrated with eight antenna elements at the output ports of the Butler matrix. The proposed multibeam array antenna was fabricated using a low dielectric constant and a low loss tangent substrate. The dimensions of the multibeam array antenna were 88 × 106 × 0.254 mm 3 . The Butler matrix achieved low insertion losses and low phase error with average values of 2.5 dB and less than ±10 • at 28 GHz, respectively. The measured return losses were less than −10 dB at 28 GHz. The measured radiation patterns were obtained and eight main beams were pointed at ±6 • , ±18 • , ±30 • , and ±44 • with measured gains between 9 dBi and 14 dBi.

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