NGMN backs MRSS as baseline for 5G-to-6G migration

The Next Generation Mobile Networks Alliance has issued updated guidance on 5G-to-6G migration, saying Multi-RAT Spectrum Sharing should remain the baseline approach.

The updated position offers cautious support for MRSS rather than unqualified backing. More evidence is still needed on efficiency, implementation feasibility, performance and hardware requirements before it can be treated as the preferred route in practice.

The guidance comes as operators and vendors consider how to introduce future 6G networks without repeating the complexity that marked parts of the 5G rollout. Any migration path beyond MRSS, NGMN said, should be judged against deployment need, hardware impact, implementation feasibility, total cost of ownership and overall commercial viability.

That position puts cost and operational disruption at the centre of the debate. It also signals that mobile operators want standards discussions to focus less on the number of technical options and more on whether those options can be introduced without adding unnecessary complexity.

Operator priorities

NGMN has also urged the industry to address a broader architectural question about the future core network. Stakeholders need to decide whether a 6G Core should be treated as an evolution of 5G Core or as a more distinct design, because that choice would affect user equipment, radio access networks, operational complexity and the value of different migration options.

The issue matters because migration choices at the radio layer cannot be separated from decisions in the core network. If 6G requires a more distinct core architecture, operators could face wider changes across devices, networks and operations than spectrum-sharing discussions alone would suggest.

Laurent Leboucher, Chairman of the NGMN Alliance Board and Orange Group CTO and EVP Networks, outlined the group's view of the trade-offs involved. "The 5G to 6G migration path is an essential component of the 6G design, because it will determine the cost of the 6G deployment and hence the economic viability of the associated new features and capabilities. MRSS is the most promising mechanism as it allows flexible reuse of the legacy 5G spectrum for deploying 6G services, with limited impact on 5G capacity and user experience.

"Nevertheless, to be deployable, the MRSS design has to satisfy a number of criteria, including low control signalling overhead and working efficiently with the 5G hardware already in the field. With this guidance, NGMN emphasises the important criteria to take into account in the design of the 5G-6G migration solutions, from the perspective of both the impact on end-users and the severe business implications for operators and the industry."

His comments underline a central concern among operators: how to introduce 6G services in existing spectrum bands while limiting the need for major hardware replacement. In effect, NGMN is arguing that migration should be shaped as much by what can be delivered on deployed infrastructure as by what is technically possible in a new standard.

Fragmentation risk

The alliance's updated guidance also reflects concerns that too many migration paths could divide the market. Multiple approaches may offer flexibility, but they can also create fragmentation in standards, product development and network deployment.

Guangyi Liu, Chief Expert of China Mobile and NGMN Board Director, pointed directly to that risk. "5G taught us a hard lesson: too many migration options led to fragmentation, delayed rollouts, and costly retrofits. For 6G, let's not repeat that - with 6G Standalone as the target, MRSS should be our baseline, and any alternative needs to prove it is worth the extra complexity."

That warning suggests operators are trying to influence 6G planning earlier than they did in previous cycles. By pressing for a baseline approach now, they are seeking to narrow the field before standards work locks in a wider set of options that could later raise costs and slow deployment.

Luke Ibbetson of Vodafone also stressed the importance of reusing existing assets. "6G must build on the strong foundations of 5G and not trigger unnecessary replacement of deployed infrastructure. Efficient spectrum sharing allows new 6G radio capabilities to be introduced as a smooth, software driven upgrade in existing frequency bands. MRSS technology is fundamental to this goal, and it must be delivered with low operational overhead and a demonstrable ability to maximise hardware reuse."

NGMN describes itself as an operator-driven alliance that feeds requirements into standards bodies and produces guidance for the mobile sector. Its latest intervention shows operators trying to shape not just the technical design of 6G, but also the commercial and operational assumptions behind it, with hardware reuse and low operational overhead emerging as key tests for any migration model.