3GPP has ended up in a potentially complex situation, where we now have two network architectures on the table.

Consequently, depending on how communication service providers deploy their radio networks, which technology they use for coverage bands, and which technology they use for capacity bands, they may end up with different core network solutions. 

5G Core (5GC) is the main part of 5G mobile, it handles the reliable and secure network connectivity for users to provide the services. 5G Core has multiple responsibilities as a variety of essential functions in the mobile network, such as connectivity and mobility management, subscriber data management and policy management, authentication and authorization, and some others. 5G Network functions support mainly cloud-native features and is service-based (SBA).

4G EPC (Evolved Packet Core) on another side is the framework to provide the data and voice services over the 4G LTE (Long-Term Evolution) Network. In 4G LTE network, Voice is also packetized over an IP network, considered the same as data, and routed on the same channel. Before it, 2G and 3G architecture had different channels for voice and data as circuit-switched and packet-switched respectively.

Difference Between 5G Core (5GC) and 4G Evolved Packet Core (EPC)

Below are the main differences between 5G Core (5GC) and 4G Evolved Packet Core (EPC):

1. Service-Based Architecture (SBA)

The major difference between 5G Core (5GC) compared to 4G is that 5GC’s control plane (CP) functions interact in a Service-Based Architecture (SBA). 

A key Network Function (NF) of SBA is the Network Repository Function (NRF), which provides NF service registration and discovery, enabling NFs to identify appropriate services in one another. 

SBA principles apply to interfaces between CP functions within 5GC only, so interfaces toward Radio Access Network (RAN), user equipment, or user plane (UP) functions (N1, N2, N3, N4, N6, and N9) are excluded.

2. Structure

Another major difference in 5GC’s Control Plane is the structure because it has a different functional separation of Access and Mobility Functions (AMF) and Session Management Functions (SMF). 

5GC includes the separation of User Plane and Control Plane functions of the gateway, which was an evolution of the gateway CP/UP separation (CUPS) introduced in EPC Release 14. 

Other changes include a separate Authentication Server (AUSF) and several new functions, such as the Network Slice Selection Function (NSSF) and the Network Exposure Function (NEF). 

3. Dual-Mode Approach to Core Evolution

Considering service providers’ concerns as of now, for protecting investments already made in the network, 5G allows full integration of new cloud-native NFs with Virtual or Physical NFs (VNFs and PNFs) in the same network and offers different migration paths to bring all NFs into a full cloud-native, dual-mode 5G Core over time. 

This makes deployment more flexible, allows for interworking with legacy networks, and smooth evolution to 5GC. 

4. Network Slice Selection Function (NSSF)

Network Slice Selection Function (NSSF) solution to select the optimal network slice available for the service requested by the user in the 5G environment where various services are provided.

Network Slice Selection Function (NSSF) selects the network slicing instance (NSI), determines the allowed network slice selection assistance information (NSSAI), and sets AMF to serve the UE.

5. Control and User Plane Separation

5G Core has been further enhanced with new features on SMF and UPF on Gateway.