The third paper in this special issue [3] focuses on the problem of placing the different baseband processing units on processing pool facilities spread over the network, taking into account the latency requirements of the traffic flows. [PERSON] presents a mixed integer linear programming (MILP) formulation to optimally solve this problem. As stated by the author, his formulation is feasible for network instances with few units and nodes where good-quality solutions are found; the development of heuristics or more advanced MILP techniques is required for larger network scenarios. The routing and spectrum allocation (RSA) planning problem related to designing optical networks has been the focus of many studies in the last 10 years. Since the complexity of the optimization problem is NP-complete, heuristic and meta-heuristic solutions have been proposed to solve it in a reasonable period of time with good-quality results. In the fourth paper, [PERSON] et al. [4] compare several nature-inspired metaheuristic optimization algorithms to minimize the capital expenditure in optical networks. The comparison is performed using the same solution model for different network topologies. [PERSON] et al. [5] propose a collaborative decision-making process for cognitive radio networks. The novelty of this work is the proposal and structure of the developed collaborative model that acts as a bidirectional source of information. The decision-making process was carried out with multi-criteria techniques, namely Feedback Fuzzy, the Analytical Hierarchical Process, and Simple Additive Weighting, which have shown excellent results. [PERSON] et al. [6] contribute to this special issue with a paper dealing with the Virtual Network Function (VNF) placement problem in Micro Data Center (MDC)/Cloud Data Center (CDC) edge computing networks. In particular, the authors propose a VNF placement solution that takes into account the latency and resource requirements imposed by the service function chains (SFC), the bandwidth and resource restrictions imposed by the network and micro data centers, and the instantiation cost of VNFs. The authors formulate a formal Integer Linear Programming (ILP) model and propose a heuristic solution, obtaining the target cost similarly to state-of-the-art approaches and, at the same time, a better performance in terms of non-allocated SFCs. In the context of next-generation wireless communications systems, [PERSON] et al. [7] propose a distributed cell clustering algorithm that maximizes the overall downlink throughput of the Joint Processing Coordinated Multipoint Transmission (JP-CoMP) scheme. The proposed algorithm consistently provides a higher performance compared to conventional methods in terms of both average user equipment throughput and average edge user throughput. Despite all of the advantages, the message update procedure in the proposed algorithm causes latency issues; however, for most typical applications of JP-CoMP, the latency issue would not be critical. Blockchain technology is essentially a decentralized database maintained by the collective, and it is now widely applied in various fields. [PERSON] et al. [8] propose a blockchain-based secure inter-hospital Electronic Medical Report (EMR) sharing system. Through the programmatic authorization mechanism by smart contracts, the security of EMR is guaranteed. In addition to the essential mutual authentication, the proposed scheme also provides and guarantees data integrity, nonrepudiation, user un-traceability, forward and backward secrecy, and resistance to replay attacks. The spectrally-spatially flexible optical network (SS-FON) combines the adaptive use of different modulation formats and multi-carrier transmission with the parallel transmission of a number of co-propagating spatial modes in appropriately designed optical fibers. In the context of this new evolution of optical networks, [PERSON] et al. [9] address the problem of the optimal placement of transponders operating in a so-called back-to-back configuration.