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An overview of the 5G mobile network architecture

V. Network  Slicing

Next-generation 5G networks will cater to a wide range of new business verticals. It will facilitate
autonomous driving, e-health-care, IoT usage for smart cities, and remote operation of machinery. All such applications require connectivity, but with varying network service characteristics. For instance, the mobile broadband requires high data rates to be supported, whereas a mission-critical service like telesurgery focuses on low latency as a service requirement. The network performance is characterized in terms of latency, availability, data rate, QoS, security and many other parameters. One of the key technical challenges faced by service providers is to deliver this whole spectrum of network performance characteristics, as the requirements vary across services. The ability to customize the network depending on the service specifications is desired.

These services also pose a business challenge. The need to strike the right balance between cost-optimized and performance-optimized implementations will be crucial to profitability. It will enable industries to introduce new services and products into the market rapidly, along with expanding upon their existing services.

Such notions of customization, flexibility and scalability could be introduced in the network using the
concept of Network Slicing [31].

A. Concept of Network Slicing

Network slicing is a way of abstracting the network into slices, each forming an end-to-end logically
isolated network, dedicated to various types of services. Each slice is composed of network functions, the network resources to run these functions and other policy information. For instance, a network can be sliced into a slice for autonomous cars, a slice for smartphones, a slice for IoT devices etc.

Network slicing is driven by the techniques of Software Defined Networking (SDN) [32] and Network Function Virtualization (NFV) [33]. NFV is a network architecture which virtualizes the network functions previously realized on costly hardware platforms as software functions by installing them on a cloud computing environment or on lowcost hardwares. SDN is used in separating the control plane and the user plane, and to enable the control of data.

eq17Figure 8: Network Slicing, adapted from [34].


Figure 8 shows various entities involved and the roles they play in network slicing. Network function such
as MME, PCRF and S/P GW in the packet core and DU in RAN are virtualized (NFV) by installing them on Virtual Machines (VMs) which are deployed on a commercial server and not on a dedicated network equipment. SDN helps in the network connectivity between VMs in edge cloud and core clouds. There lies a virtualized server in the core cloud. In the Hypervisor of that server, a router is run. SDN controller creates SDN tunnels between the VMs of core cloud and the router. Similarly tunnels are also created between the VMs of the edge cloud and the router. The mapping of the two tunnels is also handled by the SDN controller thereby, creating an end-to-end network slice.

The combination of NFV and SDN, makes it possible to move parts of the core network closer to the edge or users, thus reducing the end-to-end network latency. In a different use-case of massive IoT slice, the core cloud is made without the mobility management feature which makes it light duty and simpler to support massive connections. The UHD slice is configured such that the 5G core (UP) and the cache server are moved in the edge cloud, enabling high performance video cache.

For different services, the slices could be assigned different types of resources. This provides flexibility in terms of placement of these virtualized network functions as well, allowing the design of slices to meet the service requirements. Together, these slices can support a large number of services and make the operations cost-effective.

B. Benefits
There are several benefits of network slicing, as explained below.
Customized Connectivity. Current mobile networks only provide a particular set of control functions and cannot customize them for a certain service type. 5G networks make the network flexible, enabling the possibility of creating a customized network for a given service requirement. They also eradicate the need of a dedicated network to be created for each service as the same network can now handle multiple use-cases.

Network Efficiency.  With slicing different services will operate with the appropriate amount of resources required by them on contrary to having a dedicated network architecture. For instance, the massive IoT use case would not need PCRF entity. A slice with just the necessary resources can be created, making the use of network resources more efficiently.

Agility.  5G network slices can be generated, maintained or terminated automatically depending on the demand requirements from the service. Thus, it will now be possible to support new businesses which probably would not have had technical or economic sense earlier. An industry can just specify the slicing requirements and a suitable network slice is generated for its use.

Security. Network Slicing essentially slices the physical network into many virtual end-to-end networks. Every slice is logically isolated from each other, thus the traffic from one slice cannot interfere the other. Logical isolation also implies that an error or a fault in a particular slice will not effect on the functioning of other slices.

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