The 6G core divide

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(Source: Siarhei Yurchanka/Alamy Stock Photo)

Every mobile generation begins with a familiar cycle—what to keep, what to remove and what to improve. The 4G and 5G standards took the whiteboarding approach, including engineering designs from scratch with grand visions, fewer constraints and greater freedom. These were different G-cycles, where operators worried less about cost, use cases and monetization.

6G core discussions are different. Stakeholders are not just debating low level protocol tweaks, such as swapping traditional telco signaling for web native interfaces as in 5G. Rather, these discussions represent a high stakes tug-of-war between evolution and reinvention. Significantly, core architecture decisions will dictate who controls intelligence and service execution down to the device.

This time, operators are still carrying capital costs from 5G standalone (5G SA) deployments without delivering substantial commercial returns. Seventeen major operators submitted a joint position paper ahead of Madrid, stressing (again) upgradable paths, investment protection and a migration they can afford rather than rip-and-replace core reinvention.

Related:Ericsson and Nokia face 6G teething troubles and telco pushback

Three competing directions

After the initial core proposals phase, the SA2 working group meeting in Prague sought common architectural principles to consolidate overlapping designs and streamline decision-making. Two fundamental points have emerged: how to handle or embed AI functionality and what to do with non-access stratum (NAS) signaling.

NAS is the secure signaling pipeline between the device and core network, handling authentication, encryption, mobility management and session setup. Mobile architectures have relied on it as a foundational pillar since 2G (GSM), embedding it in device baseband silicon and SIM security frameworks.

Reworking NAS requires modem redesign, core security procedure overhaul and device backward-compatibility planning. Inside 3GPP SA2, the study phase has identified three candidate directions for the core network (based on AI functionalities):

Related:6G talks raise more questions about 5G migration options

Notes: *Apple doesn’t specify AI realization, so it fits into Directions 1 or 2.

For an extended version of this article, with more technical detail and context, download this free-to-view Omdia white paper: 6G core system architecture: Competing directions and implications.

Of these three paths, the first (Direction 1, separate AI domain) has gained the most traction among Western operators and vendors (T-Mobile USA, Verizon, Deutsche Telekom, Nokia, Ericsson, NEC, NVIDIA and, to some extent, Apple). Anchoring the core to the 5G service-based architecture (SBA) interface preserves 5G core investments while letting intent handling mature alongside existing services.

Related:T-Mobile requests to test 2.7GHz and 4GHz in 6G spectrum pipeline

Delegates are discussing a compromise: a partial merge of Directions 1 and 2 (AI functionality in 6G NFs), in which operators could separate the AI domain while introducing modular routing to prevent potential chokepoints in the AMF. This means a practical tweak to the NAS routing functionality to ensure it can operate standalone or be combined with core functions like the AMF.

Figure 1: Direction 1: Separate AI domain

Direction 3 (AI/agent-handled connectivity) offers a bolder, forward-looking autonomous agent fabric in which fixed signaling is replaced by dynamic intent coordination and deeply integrated AI operations. Aligned largely with Chinese vendors and operators, it reinvents substantial parts of the core rather than retrofitting AI, but deviates from the 6G guiding principles of lean, simple design and evolutionary 5G SA migration.

The catch: Edge device and service operation

Even if the plenary reaches consensus around Direction 1, architectural disruption moves out to the terminal (the UE AI domain client). Historically, mobile devices negotiated radio access and sessions via NAS signaling, while applications handled everything else. By formalizing an intent-driven AI domain in the core network and device (Direction 1), 3GPP is fundamentally changing device architecture.

Direction 1 is not just tweaking how a modem connects to the RAN. It standardizes UE AI domain client interfaces to the core by creating an application-layer intent client to understand what the user or agent wants and a 3GPP AI domain client to translate that into secure network signaling. This approach has commercial implications:

How 3GPP balances operator control with device ecosystem openness remains a critically unresolved question.

Splintering

In previous generations, 3GPP could occasionally resolve deadlocks by leaving some contentious variations as optional vendor implementations outside 3GPP specifications. For 6G, architectural divergence is too deep for this workaround.

Direction 3 is the revolutionary clean slate design that introduces native agentic routing and independent signaling functions. The other two directions are evolutionary, but the gap between these cohorts risks a splintered global standard. This could leave operators managing two divergent cores: a revolutionary single-vendor solution in Chinese domestic markets and an evolutionary multi-vendor architecture in the rest of the world.

Closing thoughts

In the past, 3GPP has succeeded by balancing technical ambition and commercial pragmatism. While a merger of Directions 1 and 2 looks most likely, the clock is ticking. Post-Madrid discussions must finalize an architecture by November and deliver a system solid enough to keep a divided industry unified under a single global standard.

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