Anyone expecting the recent 3GPP plenary meetings in Madrid to deliver a final, definitive decision on 5G-to-6G migration scenarios was left disappointed. The international standards group found itself unable to agree on which options—and how many of them—should be permitted within the upcoming 6G migration architecture. Consequently, the organization has chosen to delay these high-stakes decisions until its next major gathering, which is scheduled to take place in December in Boston.
Despite the lack of an immediate consensus on the full architectural framework, one foundational element has emerged with absolute clarity: the baseline for 6G migration will rely on multi-radio access technology spectrum sharing, commonly referred to as MRSS. This critical mechanism is designed to allow next-generation 6G networks to be deployed within spectrum bands that are actively shared with existing 5G infrastructure. Telecom operators view this capability as an absolute necessity to ensure that early 6G rollouts achieve decent geographic coverage—leveraging 5G’s lower spectrum bands—alongside the necessary capacity and overall performance. Furthermore, MRSS could potentially allow network operators to reuse a portion of their existing 5G radio access network, or RAN, equipment, thereby cushioning the financial blow of deploying entirely new hardware.
The core debate currently dividing the standards community centers on whether additional migration options should be permitted alongside MRSS and, if so, precisely which ones should make the cut. There are three distinct options currently resting on the negotiating table, and the choices ultimately finalized by the 3GPP over the coming months will carry profound consequences. These decisions will directly impact the total cost, deployment velocity, and operational performance of upcoming 6G networks. Moreover, the chosen migration architecture will heavily influence how effectively operators can repurpose their valuable 5G spectrum holdings for advanced 6G services, a factor that could directly dictate the pace of subscriber growth once commercial services finally materialize.
The international standards body operates under a strict timeline, giving participants until March 2027 to work out the finer details. That milestone marks the scheduled transition of 6G work from the exploratory study phase into formal standards setting.
Weighing in on the discussions, Gabriel Brown, senior principal analyst for mobile networks at Omdia, emphasized that deliberation is both normal and necessary at this stage. Now is the right time to ask all these difficult questions, he noted, adding that there is no urgent need to force a premature decision when consensus remains elusive. The broader 3GPP community is simply not there yet, according to Brown, and taking the time to forge genuine agreement is well worth the delay.
Tough Calls for 6G
Part of the underlying reason for the indecision witnessed in Madrid stems from a current lack of absolute clarity regarding MRSS performance metrics and the precise architecture of the 6G core network. These crucial pieces of the puzzle will not be firmly determined until the December meetings, Brown explained.
The complexity of the situation is further compounded by the fact that various corporate stakeholders hold wildly divergent visions regarding the core functionality of future 6G systems. This divergence was highlighted by Emil Olbrich, president of PrimeLime consultancy, who attended the plenary sessions in Madrid and closely reviewed the numerous company submissions. Because the industry does not yet have a crystal-clear picture of what the final ecosystem will look like, Olbrich expressed approval that the standards group chose to take its time rather than rushing into a hasty decision that would carry immense, long-term industry impact.
Olbrich summarized the three primary architectural options under consideration in a detailed public update. Among these proposals, the first option managed to secure the highest level of backing from participants, followed by the third option. Conversely, the second option—characterized by 5G-anchored dual connectivity—garnered the least support across the board. The widespread lack of enthusiasm for this second option is hardly surprising, as it bears a striking resemblance to 5G Non-standalone architecture, a transitional setup that few operators are eager to replicate in the 6G era.
It appears increasingly likely that Option 1 will secure formal agreement when the group reconvenes in December, while Option 2 will effectively fade away, and Option 3 will likely be shunted off to Service and System Aspects, one of 3GPP’s main technical specification groups, where it will quietly transform into an interworking feature rather than a standalone migration option, Olbrich predicted.
Avoiding 5G Missteps
At the same time, there is remarkably solid backing among major industry players for an approach centered exclusively on MRSS, with zero supplementary options. Olbrich pointed out that this purist stance is actively supported by heavyweight global entities including Apple, Deutsche Telekom, Ericsson, Jio, Korea Telecom, Nokia, T-Mobile, and Telstra.
From a technical perspective, utilizing MRSS alongside 6G carrier aggregation, complete with a fast handover mechanism to 5G whenever required, would represent the simplest and cleanest migration architecture imaginable, according to Omdia’s Brown. Proponents of the no-options approach argue that introducing alternative pathways inevitably means carrying forward permanent compromises into the future.
This MRSS-only stance is also the official position of the Next Generation Mobile Networks Alliance, an influential body representing many of the world’s largest telecommunications operators. In a formal paper submitted ahead of the plenary meetings, the alliance argued that any alternative migration options must present overwhelmingly strong justifications to warrant the additional standardization, implementation, and operational complexity they invariably introduce to the ecosystem.
The intense deliberations surrounding 6G migration and core architecture feel noticeably more fraught than previous standards cycles, as if the industry is being actively haunted by the strategic missteps made during the rollout of 5G.
Echoing these sentiments, Guangyi Liu, chief expert at China Mobile and a member of the NGMN board directorate, issued a stark warning in a statement accompanying the group’s white paper. According to Liu, 5G taught the global telecommunications industry a very hard lesson: introducing too many migration options ultimately led to severe market fragmentation, delayed commercial rollouts, and costly infrastructure retrofits. For 6G, the industry must avoid repeating those mistakes, he argued, establishing 6G Standalone as the definitive target while treating MRSS as the mandatory baseline, with any alternative forced to prove its worth against the extra complexity it brings.
Reflecting on the historical transition from 4G to 5G, Olbrich recalled that five distinct options were originally accepted, yet only two were ever implemented by the industry at large. At the time, stakeholders genuinely believed that offering a wider array of choices was a positive move, but hindsight has proven otherwise.
Preventing a Multi-Billion-Dollar Flop
Before the industry can fully commit to an MRSS-only framework, however, technical stakeholders agree that further studies are urgently required. Specifically, engineers need to accurately quantify the magnitude of efficiency losses that occur when 5G and 6G share the exact same spectrum pools, and understand how those losses might impact overall network performance. While a multitude of simulation results were presented during the Madrid meetings, attendees simply lacked the necessary time to fully absorb and debate the data, Olbrich noted. Nevertheless, those initial simulation findings have successfully established the technical groundwork for upcoming discussions. Initial estimates suggest that the performance efficiency loss should remain at or below the 3% threshold.
Although high expectations surrounded the Madrid summit regarding a definitive resolution on 6G migration, a prevailing sentiment suggests that arriving at no decision is vastly preferable to making the wrong one. The industry still possesses ample time to work through the existing technical uncertainties and steer the broader community toward a stable consensus.
Making a fundamental miscalculation at this juncture carries catastrophic financial consequences. As Olbrich succinctly cautioned, getting that decision wrong risks producing a multi-billion-dollar flop. Viewed through that pragmatic lens, taking an extra three months to deliberate and get the architecture right appears to be an investment well worth making.
