5G is no longer something that is coming down the line, it is here and it will impact consumers and enterprises alike. In simple terms, 5G will be up to 100x faster than current 4G and 10x faster than the broadband connectivity that we are used to. With this speed the promise of other technology trends like IoT, AR, VR, Edge Computing and more really become possible.
One of the distinct key features of the 5G system architecture is network slicing. 4G supported certain aspects of this with the functionality for dedicated Core Networks. Compared to this 5G network slicing is a more powerful concept and includes the whole PLMN. Within the scope of the 3GPP 5G system architecture, a network slice refers to the set of 3GPP defined features and functionalities that together form a complete PLMN for providing services to UEs. Network slicing allows for controlled composition of a PLMN from the specified network functions with their specifics and provided services that are required for a specific usage scenario.
Earlier system architectures enabled what was typically a single deployment of a PLMN to provide all features, capabilities and services required for all wanted usage scenarios. Much of the capabilities and features provided by the single, common deployment was in fact required for only a subset of the PLMN’s users/UEs. Network slicing enables the network operator to deploy multiple, independent PLMNs where each is customized by instantiating only the features, capabilities and services required to satisfy the subset of the served users/UEs or a related business customer needs.
The very abstract representation below shows an example of a PLMN deploying four network slices. Each includes all that is necessary to form a complete PLMN. The two network slices for smartphones demonstrate that an operator may deploy multiple network slices with exactly the same system features, capabilities and services, but dedicated to different business segments and therefore each possibly providing different capacity for the number of UEs and data traffic. The other slices present that there can be the differentiation between network slices also by the provided system features, capabilities and services. The M2M network slice could, for example, offer UE battery power saving features unsuitable for smartphone slices, as those features imply latencies not acceptable for typical smart phone usages.
The service-based architecture together with softwarization and virtualization provides the agility enabling an operator to respond to customer needs much more quickly. Dedicated and customized network slices can be deployed with the functions, features, availability and capacity as needed. Typically, such deployments will be based on a service level agreement. Further, an operator may benefit by applying virtualization, platforms and management infrastructure commonly for 3GPP-specific and for other network capabilities not defined by 3GPP, but that a network operator may need or want to deploy in his network or administrative domain. This allows for a flexible assignment of the same resources as needs and priorities change over time.
Deployments of both the smaller scope of the 3GPP defined functionality but also those of the larger scope of all that is deployed within an operator’s administrative domain are both commonly termed a “network”. Because of this ambiguity and as the term “slicing” is used in industry and academia for slicing of virtually any kind of (network) resources, it is important to emphasize that the 3GPP system architecture specifications define network slicing only within the scope of 3GPP specified resources, i.e. that what specifically composes a PLMN. This doesn’t hinder a PLMN network slice deployment from using e.g. sliced transport network resources. Please note, however, that the latter is fully independent of the scope of the 3GPP system architecture description. Pursuing the example further, PLMN slices can be deployed with as well as without sliced transport network resources.
The above figure presents more specifics of 3GPP network slicing. In that figure, network slice #3 is a straightforward deployment where all network functions serve a single network slice only. The figure also shows how a UE receives service from multiple network slices, #1 and #2. In such deployments, there are network functions in common for a set of slices, including the AMF and the related policy control (PCF) and network function services repository (NRF). This is because there is a single access control and mobility management instance per UE that is responsible for all services of a UE. The user plane services, specifically the data services, can be obtained via multiple, separate network slices. In the figure, slice #1 provides the UE with data services for Data Network #1, and slice #2 for Data Network #2. Those slices and the data services are independent of each other apart from interaction with common access and mobility control that applies for all services of the user/UE. This makes it possible to tailor each slice for e.g. different QoS data services or different application functions, all determined by means of the policy control framework.
Above discussion has highlighted one of the advancements of the 3GPP system architecture introduced with Phase 1 of 5G. Studies concerning Phase 2 of 5G will begin in the first quarter of 2018
References & specifications
- TS 23.501 – System Architecture for the 5G System; Stage 2
- TS 23.502 – Procedures for the 5G System; Stage 2
- TS 23.503 – Policy and Charging Control Framework for the 5G System; Stage 2
