The Evolution of Core Networks in 6G: A Pragmatic Approach

One of the biggest challenges in deploying Standalone (SA) 5G has been the implementation of the 5G Core (5GC) network. While the transition from a reference point architecture to a Service-Based Architecture (SBA) was conceptually straightforward, the need to support legacy services introduced complexities that required time, effort, and financial investment. As a result, the transition process has been long and arduous for many operators.

Key Challenges in 5G Core Deployment

Several challenges have emerged with the adoption of 5GC:

  • Cloud-Native Transformation – The move to a cloud-native core requires new architectures, skill sets, and operational models, necessitating extensive retraining of teams.
  • Interoperability in a Multi-Vendor Environment – The software-based nature of 5GC allows a multi-vendor approach, but this adds complexity when integrating different platforms.
  • Security and Trust – A distributed, software-defined architecture increases the attack surface and introduces new vulnerabilities in cloud-native environments.
  • Regulatory and Compliance Issues – Operators must navigate differing national regulations concerning data sovereignty, network exposure, and lawful interception.
  • Complex Migration Paths – Many operators continue to rely on 4G EPC in 5G Non-Standalone (NSA) deployments, making the transition to a full SA 5GC a phased and costly endeavour.

Some operators seized the opportunity to modernise their entire core infrastructure, including EPC and fixed network cores, aligning them with cloud-native principles. However, this has proven to be a multi-year process, with some Communication Service Providers (CSPs) only now seeing the full benefits of their investments.

6G Core: Evolution, Not Revolution

Given the significant challenges faced during 5GC deployment, there is reluctance among many operators to undertake a similar transition in 6G. As a result, industry players—including vendors, operators, and researchers—are converging on the idea that the 6G Core will largely be an evolution of the 5G Core, incorporating additional Network Functions (NFs) rather than requiring a complete overhaul. This approach is evident in the Hexa-X-II high-level architecture above, which shows a 6G RAN connected to an evolved 5GC.

The Hexa-X-II deliverable D2.1 Draft Foundation for 6G System Design provides further insights into this evolutionary approach, detailing how new NFs can be integrated while maintaining the core principles of 5GC.

Ericsson’s 6G Core Architecture Proposal

Ericsson’s Technology Review article 6G Network Architecture – A Proposal for Early Alignment reinforces the evolutionary approach by highlighting key aspects of 5GC that can be extended into 6G. The article notes that:

  • The 5GC’s SBA has already demonstrated extensibility, with the number of NFs increasing from 22 in 3GPP Release 15 to 45 in Release 17.
  • The number of Service-Based Interfaces (SBIs) has grown even more rapidly, surpassing 110 in Release 17.
  • Increased flexibility in 5GC, while beneficial, has also introduced complexity in standardisation, development, and deployment.
  • Future evolution should focus on minimising complexity while enabling new functionalities, leveraging automation to manage operational challenges.
  • 6G will need to support emerging use cases such as immersive communications, network sensing, and zero-energy devices while ensuring continuity with existing deployment models and regulatory requirements.

Ericsson’s proposed architecture maintains the principles of horizontal separation between NFs, the underlying platform, and end-to-end management. This ensures that 6G remains manageable while benefiting from the cloud-native flexibility of 5GC.

A Practical Path Forward

For 6G to achieve widespread adoption, it must build on the success of 5GC rather than demand an entirely new core network. The industry consensus is that 6G access technology should work with an evolved 5G Core, requiring only incremental enhancements in the form of new NFs. Introducing a radically different architecture risks delays, increased costs, and resistance from operators who have only recently completed their 5G transformations.

By maintaining continuity with 5GC while selectively enhancing its capabilities, 6G can achieve rapid deployment, cost efficiency, and widespread acceptance—ensuring a smoother transition for operators and users alike.

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