Fifth Generation (5G) is here to accelerate the digitization of economies and society, and open up innovation opportunities for verticals. A myriad of 5G-enabled use cases has been identified across disparate sectors like tourism, retail industry, and manufacturing. Many of the networks of these use cases are expected to be private networks, that is, networks intended for the exclusive use of an enterprise customer. This article provides an overview of the technical aspects in private 5G networks. We first identify the key requirements and enabling solutions for private 5G networks. Then, we review the latest 3rd Generation Partnership Project (3GPP) Release 16 capabilities to support private 5G networks. Next, we provide architecture proposals for single site private networks, including the scenario in which the radio access network (RAN) is shared. Afterwards, we address mobility and multi-site private 5G network scenarios. Finally, we identify key challenges for private 5G networks.

Radio Access Network (RAN) slicing involves several challenges. In particular, the Mobile Network Operator (MNO) must ensure —before deploying each slice—that corresponding requirements can be met throughout its lifetime. For ultra-Reliable Low Latency Communication (uRLLC) slices, the MNO must guarantee the packet transmission delay within a delay budget with a certain probability. Most existing solutions focus on allocating dynamically radio resources to maximize the number of packets, whose transmission delay is within the delay budget. However, these solutions do not ensure the violation probability is below a target value in the long term. In this paper, we focus on slicing from a planning perspective. Specifically, we propose a Stochastic Network Calculus (SNC)-based model, which given the amount of radio resources allocated for a uRLLC slice, the target violation probability and the traffic demand distribution, provides the delay bound for such conditions. Additionally, we propose heuristics for planning uRLLC slices. Interestingly, such heuristics benefit from the proposed SNC-based model to compute the amount of radio resources to be assigned to each slice while its delay bound, given a target violation probability, is within the delay budget. We validate the SNC-based model and demonstrate the effectiveness of the heuristics.

Next-generation systems are anticipated to be digital platforms supporting innovative services with rapidly changing traffic patterns. To cope with this dynamicity in a cost-efficient manner, operators need advanced service management capabilities such as those provided by NFV. NFV enables operators to scale network services with higher granularity and agility than today. To this end, automation is key. In search of this automation, ETSI has defined a reference NFV framework that makes use of model-driven templates called NSDs to operate network services. For the scaling operation, an NSD defines a discrete set of instantiation levels among which a network service instance can be resized throughout its life cycle. Thus, the design of these levels is key for ensuring effective scaling. In this article, we provide an overview of the automation of the network service scaling operation in NFV, addressing the options and boundaries introduced by ETSI normative specifications. We start by providing a description of the NSD structure, focusing on how instantiation levels are constructed. For illustrative purposes, we propose an NSD for a representative network service. This NSD includes different instantiation levels that enable different ways to automatically scale this network service. Then we show the different scaling procedures the NFV framework has available, and how it may automate their triggering. Finally, we propose an ETSI-compliant workflow to describe in detail a representative scaling procedure. This workflow clarifies the interactions and information exchanges between the functional blocks in the NFV framework when performing the scaling operation.

Requirements for 5G mobile networks includes a higher flexibility, scalability, cost effectiveness and energy efficiency. Towards these goals, Software Defined Networking (SDN) and Network Functions Virtualization have been adopted in recent proposals for future mobile networks architectures because they are considered critical technologies for 5G. In this paper, we propose an X2-based handover implementation in an SDN-based and partially virtualized LTE architecture. Moreover, the architecture considered operates at link level, which provides lower latency and higher scalability. In our implementation, we use MPLS tunnels for user plane instead of GTP-U protocol, which introduces a significant overhead. To verify the correct operation of our system, we developed a simulator. It implements the messages exchange and processing of the primary network entities. Using this tool we measured the handover preparation and completion times, whose estimated values were roughly 6.94 ms and 8.31 ms, respectively, according to our experimental setup. These latencies meet the expected requirements concerning control plane delay budgets for 5G networks.

Network slicing is considered a key mechanism to serve the multitude of tenants (e.g. vertical industries) targeted by forthcoming 5G systems in a flexible and cost-efficient manner. In this paper, we present a SDN/NFV architecture with multi-tenancy support. This architecture enables a network slice provider to deploy network slice instances for multiple tenants on-the-fly, and simultaneously provision them with isolation guarantees. Following the Network Slice as-a-Service delivery model, a tenant may access a Service Catalog, selecting the slice that best fits its needs and ordering its deployment. This work provides a detailed view on the stages that a network slice provider must follow to deploy the ordered network slice instance, accommodating it into a multi-domain infrastructure, and putting it operative for tenant's consumption. These stages address critical issues identified in the literature, including (i) the mapping from high-level service requirements to network functions and infrastructure requirements, (ii) the admission control, and (iii) the specific information a network slice descriptor should have. With the proposed architecture and the recommended set of stages, network slice providers can deploy (and later operate) slice instances with great agility, flexibility, and full automation.

The standardization of radio access networks (RANs) in mobile networks has traditionally been led by the 3rd Generation Partnership Project (3GPP). However, the emergence of RAN slicing has introduced new aspects that fall outside the 3GPP scope. Among them, network virtualization enables the particularization of multiple behaviors over a common physical infrastructure. Using virtualized network functions (VNFs) that comprise customized radio functionalities, each virtualized RAN (i.e., RAN slice) could meet its specific requirements. Although the 3GPP specifies the description model to manage RAN slices, it can neither particularize the behavior of a RAN slice nor leverage the network function virtualization (NFV) descriptors to define how its VNFs can accommodate its spatial and temporal traffic demands. In this article, we propose a description model that harmonizes 3GPP and the European Telecommunication Standard Institute (ETSI)-NFV Group viewpoints to manage RAN slices. The proposed model enables the translation of RAN slice requirements into customized, virtualized radio functionalities defined through NFV descriptors. To clarify this proposal, we provide an example describing three RAN slices with disruptive requirements following our solution.