Exploring the 5G Architecture

Every new generation of cellular technology brings a fresh set of acronyms and concepts for mobile network engineers to learn. 5G is no exception. Nearly the entire architecture has been renamed, and in the core it has been fundamentally redesigned.

When 5G first launched, almost every network was NSA (Non-Standalone). NSA pairs 5G radio with a 4G core. Today the picture looks very different. SA (Standalone) 5G, with its own dedicated 5G Core, is now live with close to 100 operators worldwide. It has become the foundation for services such as network slicing, RedCap, enterprise services and 5G-Advanced. NSA still carries most 5G traffic globally, so engineers need to understand both, but SA is where the architecture continues to head.

Figure 1 - 5G Standalone Key Elements

At a high level, the 5G System has three main parts: the 5G New Radio (NR) air interface, the NG-RAN (Next Generation Radio Access Network), and the 5GC (5G Core). You can explore all of these parts in our FREE 48-hour trial, which includes Introduction to 5G and three of our other popular courses. If you want to dive into more detail, the free trial also includes full access to our acclaimed interactive network architecture tool, NetX.

The NG-RAN (Next Generation – Radio Access Network) remains a straightforward design in terms of architecture; the gNB is the main RAN node, which can operate in a DC (Dual Connectivity) mode with other gNBs or 4G eNBs. The gNB is no longer necessarily a single entity. It can be split into a RRUs, DUs, and CUs as shown within our Open RAN for 5G course.

Figure 2 - 5G Core Key Network Functions

The 5G Core is where we see the most significant architectural changes take place:

• Mobility and Session Management are Split. In 4G, the MME handles both of these responsibilities but in 5G the AMF (Access and Mobility Management Function) manages mobility and the SMF (Session Management Function) manages session.
  

• The User Plane is Unified. The 4G S-GW and P-GW user plane roles are combined in 5G into the UPF (User Plane Function), and their control roles move to the SMF. Because the user plane is now separate from the control plane, UPFs can be placed at the edge of the network for low-latency applications.

• Subscriber Data moves to the UDM. The UDM (Unified Data Management) is a centralized repository of subscriber-related information and replaces the 4G HSS.

• Policy Moves to the PCF. Policy control is just as prominent in 5G, with the PCF (Policy Control Function) performing the policy-controlling role that the PCRF (Policy and Charging Rules Function) performs in 4G.

• Network Function Finding Capabilities. The NRF (Network Repository Function) acts as a directory for the 5G Core with each function registering its services and being able to query the services of other registered network functions

If you want a more detailed discussion on these key Network Functions, feel free to check out our free course on YouTube. There are many additional functions that are found in the 5G architecture, all of which are featured in NetX and explained in the comprehensive 5G training courses that we offer.

However, perhaps the most compelling change is the notion of the Service-Based Architecture, which is the basis upon which the control elements of the 5GC will operate. That is, instead of traditional hardware platforms performing dedicated roles, the 5GC control plane will be completely virtualized, with each virtualized network function offering its services to other network functions via standardized APIs (Application Programming Interfaces) based on RESTful principles.

This article only scratches the surface of the end-to-end 5G architecture and how it operates. For details, we can offer a wide range of 5G telecoms training courses (from beginner to advanced), using several delivery options (Live onsite, Live online and On-demand).

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