[FS_ULBC] ULBC Re-Focus Proposal
Proposal: To facilitate the timely delivery of a practical ULBC solution for IMS Voice over GEO within the Rel‑20 timeline, initial standardization efforts should be confined to a baseline configuration that is strictly anchored in stable Rel‑19 service requirements and guaranteed Rel‑19 radio features (with SPS as the sole exception). It is also recommended to maintain a targeted approach regarding design constraints, performance requirements, and testing methodologies. Defining this focused scope is critical to ensure the successful completion of the anticipated Rel‑20 Work Item following the FS_ULBC Study Item, as prompt SI finalization is required before commencing any ensuing WI activities.
Concurrently, advanced features and expanded application scenarios dependent on evolving 6G Media requirements have been recognized. As these requirements are still under development and not yet established as normative, they are unsuitable for inclusion in the Rel‑20 baseline. These elements should instead be systematically addressed in a structured second phase during Rel‑21, subsequent to the stabilization of pertinent 6G requirements.
It is therefore proposed to standardize ULBC in two phases:
Rel‑20 ULBC Baseline — GEO‑focused functionality based solely on Rel‑19 service requirements and mandatory Rel‑19 features (except SPS), enabling completion of a viable ULBC baseline standard within the Rel‑20 schedule.
Rel‑21 ULBC Advanced — Extended ULBC functionality aligned with finalized 6G Media requirements and supporting application scenarios beyond Rel‑20 IMS Voice Call over GEO. Possibly also leveraging advanced UE capabilities.
This two‑phase approach ensures a deliverable ULBC baseline in Rel‑20 while providing a clear and orderly path toward an enhanced ULBC design in Rel‑21. To ensure full alignment of the ULBC systems designed in the two phases, Rel-21 ULBC Advanced should be a backward compatible extension of the Rel‑20 ULBC Baseline.
The source suggests that SA4 adopts this phased approach for ULBC standardization as working assumption.