5G End to End Network Slicing

Introduction

5G will empower new verticals, new services, and new business models that aren’t possible or practical with LTE and other legacy mobile technologies. Examples include wearables for advanced telemedicine applications, virtual/augmented reality (AR/VR), UHD video, and machine-to-machine (M2M) applications that require few millisecond latencies such as driverless cars.
These services are enabled through a key technology called network slicing and managed by an End-to-End (E2E) service orchestration.

Network Slicing will allow carriers to create virtual data pipelines for each of its data type services, thereby assuring the QoS for each service. It will also ensure the quality of data transmission for time-sensitive, mission-critical services such as connected cars.

Network Slicing Concept

The network slicing concept enables the network elements and functions to be easily configured and reused in each network slice to meet a specific requirement. The implementation of network slicing is conceived to be an end-to-end feature that includes the core network and the RAN. Each slice can have its own network architecture, engineering mechanism, and network provisioning.

Network Slicing Concept

Network slicing leverages the latest innovations in cloud mobile access and core. Combining cloud technologies with the capabilities of software-defined networking (SDN) and network function virtualization (NFV) provides the necessary tools to enable network slicing.
Virtualization technologies provide a key foundation for network slicing by enabling the use of both physical and virtual resources to create the service they are designed for.
Network slicing implementation is end-to-end from the core through the RAN. In the core, NFV and SDN virtualize the network elements and functions in each slice to meet its own requirement. In the RAN, slicing can be built on physical radio resources (e.g., a transmission point, spectrum, time) or on logical resources abstracted from physical radio resources.

Network Slicing Architecture

The network slicing architecture contains access slices (both radio access and fixed access), core network (CN) slices, and the selection function that connects these slices into a complete network slice comprised of both the access network and the CN. The selection function routes communications to an appropriate Core Network slice that is fitted to provide specific services.
The criteria for defining the access slices and CN slices include the need to meet different service/application requirements and to meet different communication requirements.
Each CN slice is built from a set of network functions (NFs). An important factor in slicing is that some NFs can be used across multiple slices, while other NFs are tailored to a specific slice.

Network Slicing Architecture

To support Network Slicing, the management plane creates a group of network resources (whereby network resources can be physical, virtual or a combination thereof), it connects with the physical and virtual network and service functions as appropriate, and it instantiates all of the network and service functions assigned to the slice.
For slice operations, the control plane takes over the governing of all the network resources, network functions, and service functions assigned to the slice. It (re-) configures them as appropriate and as per elasticity needs, in order to provide an end-to-end service.

Status of Network Slicing in 5G Standards

Identification of a Network Slice is done via the Single Network Slice Selection Assistance Information (S-NSSAI). The NSSAI (Network Slice Selection Assistance Information) is a collection of S-NSSAIs. Currently, 3GPP allows up to eight (8) S-NSSAIs in the NSSAI sent in signaling messages between the UE and the Network. This means a single UE may be served by at most eight Network Slices at a time. The S-NSSAI signaled by the UE to the network, assists the network in selecting a particular Network Slice instance.
An S-NSSAI is comprised of:

A Slice/Service type (SST), which refers to the expected Network Slice behavior in terms of features and services;
A Slice Differentiator (SD), which is optional information that complements the Slice/Service type(s) to differentiate amongst multiple Network Slices of the same Slice/Service type.

The S-NSSAI may be associated with a PLMN (e.g., PLMN ID) and have network-specific values or have standard values. An S-NSSAI is used by the UE in the access network in the PLMN that the S-NSSAI is associated with.

Network Slicing in Core Network

Network slicing allows core networks to be logically separated, with each slice providing customized connectivity, and all slices running on the same, shared infrastructure, or on separate infrastructures as the operator requires.
It is likely that networks will need to be deployed using different hardware technologies, with different feature sets placed at different physical locations in the network, depending on the use case.
To support a specific set of services efficiently, a network slice should have access to different types of resources, such as infrastructure—including VPNs, cloud services, and access—as well as resources for the core network in the form of VNFs. The flexibility of 5G core networks will improve significantly by supporting a full separation of control plane and user plane, and through adopting selected SDN principles and technologies.

Example of Network Slices

Network Slicing in the RAN

When considering how network slicing is supported in the RAN, it’s important to consider two aspects:

The radio access type (RAT) that supports the network services provided by the slice.
The configuration of RAN resources to appropriately interface with and support the network slice.

Network Slicing Challenges for 5G Networks

In order to implement and use network slice functions and operations, there is a clear need to look at the complete life-cycle management characteristics of Network Slicing solutions based on the following architectural tenets:

Underlay tenet: support for an IP-based underlay data plane the transport network uses to carry that underlay.
Governance tenet: a logically centralized authority for all of the network slices in a domain.
Separation tenet: slices may be independent of each other and have an appropriate degree of isolation from each other.
Capability exposure tenet: allow each slice to present information regarding services provided by the slice (e.g., connectivity information, mobility, automaticity, etc.) to third parties, via dedicated interfaces and /or APIs, within the limits set by the operator.