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(2nd) International Workshop on System Architectures of Future Core Networks, 8 July 2025, Munich, Germany
Date: 8 July 2025
Location: DoCoMo Communications Laboratories Europe GmbH
Editor: Rui Luis Aguiar, Hans J. Einsiedler
A workshop on the evolution of the Future Core was held in NTT DoCoMo Com Laboratories in Munich on the 8th of July. The workshop agenda is the following:
Welcome and Opening
Prof Rui L. Aguiar welcomed and thanked all the participants for their availability and contributions to this workshop.
Keynote: Itsuma Tanaka
This keynote presented some potential aspirations for 6G, namely the trends of AI overloaded in environments of cloudification, IoT, and slicing. It seems clear that we will move towards 6G core in an evolutionary way, towards a more cloud-native network. There is a need to secure technology and business advantages and win the (future) market. A final comment was made on the need to assure joint development of the technology and its evolution.
Session 1: “Voice services in future – need support of the core?”
This session addressed the problem of “Voice services in future – need support of the core?”. The discussion reviewed objectives, scope and technical directions for future voice and data services over IMS and 6G. Participants examined architecture choices, interoperability considerations and standardization timelines.
A couple of topics were highlighted by the speakers and the following discussion: The arguments were centered on whether future voice services will need direct support from the 6G core, or if they can be managed as over the top (OTT) applications. Voice and IMS (details withheld) reality, 5G has not significantly accelerated IMS adoption, partly due to the slow rollout of standalone 5G core networks. Service Based Interface (SBI), despite being a key 5G core concept, is not widely used with IMS, suggesting limited readiness for radical architectural changes. The distinction between operator managed voice and IMS based services is blurring, but operator voice remains relevant due to regulation and reliability.
Key areas for 6G enhancement include reducing complexity and ensuring seamless service continuity as older technologies are retiring. The major conclusions can then be posed as the evolution of the 6G core network for voice services is shaped by regulatory obligations, entrenched technologies (like SIP and IMS), and the need for secure, high-quality connectivity. While AI and new interfaces like IMS-Data Channel offer potential, but radical changes are unlikely in the near term.
Session 2: “Completing the cloud-native transformation of the core: Strategic pathways, planning, and problems”
In this session Open6GCore was given as an example solution to reduce complexity by merging functions, and tackling the challenges (e.g. from NAS), by using a web services architecture. In terms of details, it advocated for: direct routing of NAS between RAN and NAS capable NFs, and E2E User Plane encryption: the introduction of API based functionality and modular NAS, and emphasized SBI based N2 and slicing based 6G deployment.
Session 3: “Defining requirements and priorities for the future core evolution”
On a third session, the majority of the participants highlighted the importance of sticking to the agreed 6G timeline, with a call to find a good tradeoff between radical changes and evolving 5G SA, which is not yet widely deployed. There was consensus that standardization is about external interfaces, whereas the rest of the technical details is implementation specific and different vendors having different software solutions. Efficiency and savings were identified as a key criterion for decision making, with a focus on bringing added value and efficiency to novel proposals. Practical proof points were deemed essential, motivating for use of Open6GCore to create feedback for 3GPP and other vendors. Some proposals for 6G Modularization addressed protocols like NAS, resiliency, AI powered for full automation, security and sustainability by design (but needs further definition). The discussion elaborated that the 6G Core will largely build upon established functional components from 5G, including (SBA), roaming functionalities, and various improvements in functions such as UDM, AUSF, NRF, NEF, and NWDAF, alongside User Plane transport.
Additionally, 6G may introduce novel network functions tailored to its architecture as required, and implement incremental enhancements – for instance, replacing the N4 interface with SBI or integrating a modular NAS protocol with discrete termination points within individual NAS services such as Mobility Management (MM), Session Management (SM), Policy Control (PC), Location (LOC). The presentation also considered how to enable interworking with devices that are not compatible with 5G SA, highlighting the relevance of this issue for the 6G era. The discussion noted a tension between maintaining legacy interoperability and innovation, questioning the telco industry’s capacity to influence its future.
Session 4: Way forward / Discussion on the next step, continuation of the workshop series
The workshop continued in this session with open points captured for standards bodies, follow‑up actions for contributors, and a shared intention to refine use cases and implementation paths in upcoming discussions inside these fora.
Final discussion
The workshop closes with the panel conclusions wrap-up, with 5minutes for each rapporteur, and the next steps to be addressed.
