The NGMN Alliance, the body that represents the views of a number of mobile operators, has released a short statement calling for the industry to make a capability known as Multi-RAT Spectrum Sharing (MRSS) the baseline for operators migrating from 5G to 6G.
But while NGMN repeated its committment to MRSS as the migration mechanism for 6G introduction, it also took the time to say that the industry still needs to demonstrate that MRSS can meet the operators’ requirements for performance, hardware reuse and implementation efficiency. In particular, NGMN is calling for low control-signalling overhead, efficient operation with 5G hardware already deployed in the field and evidence that MRSS can provide the required performance. It also says further work is needed on its efficiency, including support for both FDD and TDD spectrum.
The timing of the statement is explicitly intend to influence work taking place at next week’s 3GPP plenary meeting, at which both RAN and core working groups will meet. In fact, NGMN had originally hoped to introduce a fuller statement in September following a report it released in June. But it said that it was unable to do so due to “ongoing development of insights.” Notwithstanding, the body decided that it wanted to get its messaging across on MRSS – and on some maters related to core network choices – ahead of next week’s meeting.
NGMN told TMN, “There is still missing evidence about the performance / limitations of MRSS. It should remain the baseline approach for 5G-6G migration, but more evidence around its efficiency, implementation feasibility, performance capabilities and hardware requirements is still required. Until more information on these unknowns is available, it is difficult to down select other alternative migrations options. Therefore, as described in the publication, NGMN will continue to provide operator context and guidance on migration approaches from 5G to 6G for the ongoing 6G standardisation process.”
What are the MRSS concerns?
MRSS, as its name suggests, allows multiple radio access technologies to operate efficiently within the same carrier. That means an operator could introduce 6G into 5G spectrum while continuing to make full use of their existing spectrum assets. That’s important because while 6G will be introduced in new, higher bands, such as 7 GHz and 8GHz, to ensure wider coverage it will also be introduced in FR1 lower bands that already carry 5G. That is where 5G and 6G sharing will happen.
One spectre hanging over the industry is the history of DSS (Dynamic Spectrum Sharing) – the technology which first allowed 5G icons to appear on phone screens, by sharing 5G and 4G signals in the same spectrum. Unfortunately DSS suffered criticism for not working very efficiently, and impacting overall performance across 4G and 5G.
However, MRSS proponents such as Ericsson, say that it will work better than DSS because it can take advantage of 5G’s already lean signalling. This explainer article from Ericsson said, “Firstly, MRSS supports both FDD and TDD, reflecting the widespread use of both duplex modes in 5G, while DSS primarily focused on FDD. Secondly, MRSS achieves significantly lower overhead and higher efficiency, thanks to the ultra-lean design of 5G. This contrasts with 4G systems, which rely on many always-on signals.”
Ericsson also showed a working demo of MRSS with Apple at this year’s Mobile World Congress in Barcelona. According to Ericsson, “The live over-the-air demo showed real-time interoperability between 5G and a simulated 6G system, validating MRSS performance in a real implementation and complemented with simulations of a large-scale deployment scenario – a big step forward compared to our MRSS demo at MWC 2025.”
NGMN’s performance concerns
The September 2026 NGMN statement is clearly concerned about addressing performance issues.
It attributed the following to Orange’s Laurent Leboucher, Chairman of the NGMN Alliance Board and Orange Group CTO and EVP Networks. He said: “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.
Vodafone’s Luke Ibbetson added, “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.”
Gabriel Brown, Senior Principal Analyst, Mobile Networks, Omdia, told TMN that although MRSS has been the proposed solution for two to three years, NGMN was “right to be cautious”.
“Operators are remembering DSS,” he said. “Vendors will say it works but in reality it is only on this or that combination of equipment or configuration. So they [the operators] are not convinced – but they want to be convinced.”
Brown also noted that vendors themselves are not committing to the exact mechanisms, such as pilot signals, that will enable MRSS because they themselves don’t know what the standards will call for. Will MRSS work, for example, only on more recent 5G-A equipment, or also on older 5G networks that may not have been amoritised by the time of 6G’s introduction?
“There’s no point Ericsson saying they will do MRSS on all equipment from a date onwards, because they don’t know the spec yet. So they’re holding off,” Brown said.
There’s another criticism of MRSS which flips something operators might see as a bonus – re-using existing equipment – into a negative. That line of thought argues that this will tie 6G vendor decisions to 5G legacy networks, as micro-second timing required for spectrum sharing all but mandates the use of the same vendor.
Brown concedes that this is the case, but argues that this is something of a moot point in any case.
“We’ve seen this play out so many times. A challenger vendor wants a different way to add 4G or 5G – but that strategy is not successful and the learning is that operators don’t buy that model. So insisting on that for purity’s sake a waste of effort.”
Core issues
Further underlying the NGMN position is a concern that 6G could repeat what operators have come to regard as one of the less successful aspects of 5G: an abundance of technical options for RAN and core migration that increased complexity and contributed to fragmented deployment strategies.
China Mobile’s Guangyi Liu, an NGMN Board Director, put the point bluntly, arguing that 5G had taught the industry that “too many migration options led to fragmentation, delayed rollouts, and costly retrofits”.
For 6G, he said, the target should be 6G Standalone, with MRSS as the baseline and alternatives required to prove that they justify the additional complexity.
Omdia’s Brown points out that there is still much to discuss. MRSS may not be mandatory, with 6G users being simply handed over to 5G where they drop out of 6G coverage areas. There may also be those pushing for Dual Connectivity options, marrying 5G and 6G connectivity together.
Additionally Brown identifies a potential divergence of opinion on core network options. Chinese operators and vendors are keener on a fresh 6G core architecture, while Western companies are keener on a 5G Core evolution. Then there is the complication of AI, and whether 6G standards should be designing in an agentic AI core as a layer over the 6G core itself.
“In principle, the core network architecture and MRSS are decoupled – which is the advantage of being Stand Alone on day one. In practice they are highly linked,” Brown added.
For NGMN, that link is obvious. Its update said, “6G Core architectural evolution has a significant impact on the complexity and relative value of RAN migration options. The assessment of alternatives should therefore explicitly consider whether 6GC is an evolution of 5GC or a more distinct architecture, and how this affects UE, RAN, Core Network and operational complexity.”
The results of next week’s meeting in Madrid will certainly be worth keeping an eye on.
