What Makes it 5G? The 5G Core

What Makes it 5G? The 5G Core

March 24th, 2020 - Telecom, Roaming

By Nina Le-Richardson, Director of Product Management, TNS

As the buzz of the promise of 5G grows, it’s important to understand and separate fact from fiction. In this installment, I will outline what makes 5G really 5G.

But first, a quick recap: In an earlier blog post, I posited that 5G deployments will see two emerging options out of seven defined by the Third Generation Partnership Program, a standards development organization (3GPP) – Standalone or SA and Non-standalone (NSA). You may have even seen commercials touting that in some cities 4G is faster than rival 5G.

But what makes 5G so fast is the 5G Core (5GC). The 5GC looks different from the LTE Evolved Packet Core (EPC). In an earlier blog I noted how 5G introduces new network function elements and why that matters.

With 4G, the user plane routing occurs at the Serving Gateway (SGW) and Data Packet Gateway (PGW), both critical network functions in the mobile core network. With 5G, this function occurs at the User Plane Function, or UPF.

The 5GC network looks very different from the LTE EPC network. The 5GC network has decomposed functional elements offering specific network services and is decomposed into several Service-Based Architecture (SBA) elements. This new architecture enables network capabilities exposure for fast service creation by separating the control plane from the user plane. The control plane and user plane are moved into a cloud-based environment improving scalability, flexibility and time to market.

In addition, session management and mobility management that occurs in the Mobility Management Entity (MME), are now managed by the Session Management Function, or SMF and the Access and Mobility Management Function, or AMF. In 4G, the user repository is in the HSS and in 5G the 4G functionality is handled by the Unified Data Management (UDM), a separate data source. The UDM is where generation of Authentication and Key Agreement (AKA) credentials, user identification handling, access authorization, and subscription management occur. Separating the security credentials from the session management function results in improved data consistency and reduces the network complexity.

These are the major differences with 5GC compared to EPC and network functions you need to know about:

  • A 5G core network includes the separation of User Plane Function (UPF) and Control Plane Function (CPF) functions of the gateway. This gateway evolution of the CP/UP separation (CUPS) was introduced in EPC Release 14.
  • 5GC UPF performs packet routing and forwarding, serves as a point of interconnection to the Data Network (DN), is the anchor point for the radio access technology and can be distributed to the network edge increasing bandwidth efficiencies while reducing network resources.
  • The Access and Mobility Function (AMF) provides authentication and authorization from the end-user equipment and is limited to the connection and mobility management services. The Security Anchor Function (SEAF) serves as an anchor key allowing for re-allocation of the device when a subscriber device moves between different access networks. Separating the AMF from SEAF reduces the signaling load on the home network.
  • 5G NAS (Non-Access Stratum) also provides enhanced security over 4G and includes procedures related to the MME and SMF. We will discuss security further in a separate blog.
  • Network Repository Function (NRF) is a key Network Function of SBA. It provides NF service registration and discovery which enables NFs to identify appropriate services in one another.
  • There is also a separate Authentication Server (AUSF) and several new functions including the Network Slice Selection Function (NSSF) and the Network Exposure Function (NEF), which is now part of a new function.

Session management – session establishment, modification and release, formerly part of MME is now a part of a new network function called the Session Management Function (SMF). This granular approach allows networks to become more resilient networks.

The changes in the network and security architecture between the 5GC and the LTE EPC are significant in moving to an SBA that will allow features that are delivered to be massively scalable, highly reliable and support automated operations.

In summary, the 5G core is what makes 5G so fast and as the buzz around 5G continues as the development speeds up around the globe, keep checking our blog page and we will bring you information along with the latest industry developments.

Coming Soon – Blog #6 5G Network Slicing, this blog will give you an in-depth insight into 5G Network Virtualization, Network Slicing, and Orchestration

Read our previous posts in this series  “What to Expect with 5G Roaming”, “5G Non-Standalone vs 5G Standalone”, “LTE Has Gas in the Tank” and “The 5G Hype

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