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What is 5G Service Based Architecture?

The 5G core network architecture is designed to be cloud native making use of NFV (Network Function Virtualisation) and SDN (Software Defined Networking). NFV is used to decouple the logical function of a network element from its associated hardware and implement that function in software as a VNF (Virtualised Network Function). The VNF may be run on general purpose, off the shelf computing platforms.

The VNF may be run on general purpose, off the shelf computing platforms. The main feature of SDN is a clear separation between control and user plane functions. SDN supports centralisation of control plane functionality while at the same time supporting distribution of user plane functions which may be located close to the network edge in support of low latency communications.

What is 5G network slicing?

NFV and SDN provide an operator with a flexible underlying resource. By combining the services offered by a set of VNFs an operator may build complete virtual logical networks which can be run on shared underlying physical hardware. Each virtual logical network is referred to as a network slice.

A network slice may be optimised to satisfy the requirements of a particular use case. For example, a network operator might use different network slices for each of the main 5G use cases, i.e. eMBB, mMTC and URLLC slices optimised for high data rates, high connection densities and low latencies respectively.

          Want to know more about 5G Network Slicing? We’ve recently introduced a one day 5G Network Slicing course we think you’ll find interesting.

The 5G core network

The 5G core network is based on NFV and SDN principles in the design of the SBA (Service Based Architecture). Traditionally cellular networks have been designed using a point-to-point architecture defining reference points between any pair of communicating NFs (network functions), typically with a protocol defined per interface. In this scenario a single network function required to communicate with a number of other network functions must support multiple interfaces and protocol types.

In contrast to the reference point architecture, NFs in the SBA have a single interface through which they offer services to other NFs. This interface is known as a SBI (Service Base Interface). An NF may offer one or more NFS (Network Function Services) via the SBI.

A NF may offer one or more NFS (Network Function Services) via the SBI. These services are offered to other NFs using a well-defined API (Application Programming Interface). Newly initiated NFs register with the 5G NRF (Network Repository Function) providing their identity, service profile and address. A NF can query the NRF to discover which NFs of interest are available within the SBA, the NFS they offer, the servers they are hosted on and the network slices they support.

A NFS may offer a number of individual operations all of which are defined in the API for the SBI. Each operation is named using the scheme Nnfname_ServiceName_ServiceOperation, which identify the service-based interface, the network function service and the service operation respectively. A NF offering a service is the service producer, a NF using the service is the service consumer.

The use of service based interfaces promotes the re-use of signalling procedures within the system. For example, a service offered by an NF may be used by a number of other NFs using the same signalling procedure defined by the API for that service.

Network functions within the 5GC Control Plane use service-based interfaces for their interactions. However, in Release 15 not all network components use the SBI approach; this is true of the radio access network and functions in user plane.

Want to know more about 5G Service Based Architecture?

If you’d like to find out more it’s worth considering one of the latest additions to our 5G training curriculum, our new 5G Service Based Architecture and Core Network course. This is a 2 day technical deep-dive intended for those involved in the design, deployment and development of the 5G Service Based Architecture and the 5G Core. If you would like to book a place or want further information, please get in touch.

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About the author

Jeff Cartwright is a telecoms trainer whose expertise extends across a wide range of technologies both fixed and mobile. He specializes in transport systems, signalling systems including SS7 and Intelligent Networks as well as VoIP and IMS protocols. Before joining Wray Castle Jeff worked for the Royal Air Force as an Aviation Engineer with responsibilities for first- and second-line maintenance of sophisticated electronic systems.

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