## 3 5G-Related Work  
This section provides an overview of the development of 5G network service orchestration. Currently, in addition to International Telecommunications Union (ITU), 5G standardization is being detailed by other entities, such as 5G-PPP, 3 rd Generation Partnership Project (3 GPP), European Telecommunications Standards Institute (ETSI), and 5G Brasil, in collaboration with several international research projects [35; 36; 37; 38; 39; 40]. A number of companies and entities integrate testing projects in 5G transmissions to overcome deficiency problems in mobile communications coverage [41]. Nevertheless, studies on 5G technology [39] are not yet entirely conclusive, and there are some researchers in partnerships with companies that have worked on the topic in Asia, Europe, and the USA, among them [42; 43; 44]; however, little exploring the layers above the network layer of the 5G architecture [31]. Thus, based on the elements presented, the performance evaluation model and Orchestrator, an entity that implements the NSs for each service and guarantees the QoS E2E, the 5G network must concomitantly and transparently consider and meet all bands present in the characteristics of the frequency bands below 1 GHz, between 1 GHz and 6 GHz, and above 6 GHz [45; 46]. An issue that has arisen in some countries is whether the slicing of the 5G network will be consistent with the _network neutrality_ regulation. Some say that the practical implications for current open Internet rules are speculative at this stage concerning 5G. This is because the evolution of the different 5G elements, such as network slicing, depends not only on the occasional technological capabilities but also on the market demand, the degree of competition, the commercial strategies, and so on [14]. The design of a 5G Orchestrator must consider vertical applications under the service requirements appropriate to 5G use cases and indicators defined by the regulator. In this sense, the ITU specified several challenges at IMT-2020. According to the preliminary report on _Minimum requirements related to technical performance for IMT-2020 radio interfaces_, performance indicators must be obtained in each 5G use case [47; 48]. Thus, studies and developments at a global level have been carried out for vertical (single-domain) Orchestrators, that is, those who attend to a Telecommunications Infrastructure Provider (TIP) or Mobile Network Operator (MNO) specifically, by entities and researchers, such as Ericsson, Nokia, ETSI, and others [40, 49, 50, 51, 52, 53, 54, 55]. TIP is a provider of wireless communications infrastructures that owns all the elements necessary to sell and deliver services to an end-user, including radio spectrum allocation, as well as wireless and backhaul network infrastructures. MNO is a provider of wireless communications services that operates or controls all those elements to offer services to an end-user, including wireless and backhaul network infrastructures, customer care, provisioning computer systems, and repair organizations. 3 GPP introduced an orchestration and management architecture in [25], composed of a service management function that analyzes incoming slice requests. Thereby, converting service requirements into networking ones and an NS management function, which performs the mapping onto network resources and takes care of the Life-Cycle Management (LCM). Although the resource mapping process is carried out across different technology domains, including the RAN, transport, and core, the current 3 GPP efforts concentrate only on NSIs deployed and managed by a single administrative entity. The authors in [56] present the status of the access networks and 5G radio core defined by software and a wide range of future research challenges in terms of orchestration and control.