R1-2600038
discussion
On beam management for downlink and uplink in 6GR
From Nokia
Summary
Nokia presents 17 proposals and 15 observations on 6G beam management, advocating for a unified TCI framework as the baseline while addressing 5G NR limitations. The document covers beam indication, reporting, failure recovery, inter-cell operation, QCL simplification, and AI/ML use cases including inter-cell, beam pair, and cross-frequency prediction.
Position
Nokia proposes that the NR Release-17 unified TCI framework principles serve as the baseline for 6G beam management, while studying enhancements to address identified limitations including the limited number of indicated TCI states, reliance on periodic TRS as QCL source RS, and lack of TCI-state specific physical-layer parameter configuration. They propose a unified design for UE-initiated L1 measurement reporting framework across beam management and beam-based cell switch procedures, citing fragmentation between RAN1-led UEIBR (UCI-based) and RAN2-led LTM event-triggered reporting (MAC CE-based) as a key lesson from 5G NR. Nokia argues that the term "beam" is non-descriptive and potentially misleading for specifications and should be replaced with procedures reflecting the involved reference signals. They propose studying CBRA-based BFR with MAC CE signaling as the baseline, while also studying streamlined CFRA-based BFR and UL beam failure recovery within a unified TCI state framework. For AI/ML, Nokia presents simulation results for inter-cell beam prediction showing Top-1 beam ID accuracy exceeding 90% and Top-2 approaching 99%, and proposes studying cross-frequency beam prediction using one-sided AI/ML models for collocated deployments predicting beams across different component carriers within the same frequency range.
Key proposals
- Proposal 1 (Introduction): The term "beam management" and its extensions using the term "beam" is used for discussion only and should not be used in future RAN1 specifications.
- Proposal 2 (Beam Management Overview): Study beam management for all frequency ranges in 6G and study frequency range dependent beam refinement procedures, including procedures similar to P1, P2, and P3 in NR.
- Proposal 3 (Beam indication): Consider the principles of the NR unified TCI framework as the baseline for the 6G beam management framework, while studying enhancements to address the identified limitations and to better support advanced multi-beam, multi-TRP, and higher-frequency deployments.
- Proposal 4 (Beam reporting): In 6G CSI reporting framework, support to study both NW-scheduled, and UE-initiated measurement reporting for beam management.
- Proposal 7 (Beam Failure Recovery): Support to study CBRA based BFR, with a MAC CE based signaling as the baseline solution for 6G BFR within a unified TCI state framework.
- Proposal 10 (Inter-Cell Beam Management): Support beam management for intra- and inter-cell operation in 6G using a unified TCI state framework.
- Proposal 12 (QCL Framework): 6GR is to maintain the concept of QCL and further consider mechanisms to simplify the QCL types to increase network configuration flexibility and reduce energy consumption.
- Proposal 13 (AI/ML Overview): 5G-Adv AI/ML BM use case and the associated learnings are the baseline for 6G AI/ML BM use cases study and normative work.
- Proposal 14 (Inter-cell beam prediction): Study inter-cell beam management as an extension of Rel-19 AI/ML beam prediction by considering L1-RSRP measurements/beam ID prediction from candidate cell or from candidate cell including serving cell to reduce candidate cell beam measurement overhead and latency.
- Proposal 15 (Beam pair prediction): Study DL Tx-Rx beam pair prediction as one potential 6G AI/ML use-case.
- Proposal 16 (Cross-frequency beam prediction): Study cross-frequency beam prediction use case with one-sided AIML model to be applied in collocated scenario at least for predicting beams in different component carries within the same frequency range (e.g. 7GHz-9GHz).
- Proposal 5 (Beam reporting): Support study of a unified design for UE-initiated L1 measurement reporting framework for beam management and beam-based cell switch procedures.
- Proposal 8 (Beam Failure Recovery): Study a streamlined CFRA-based BFR, with a MAC CE BFR as baseline for 6G BFR.
- Proposal 9 (Beam Failure Recovery): Study UL beam failure recovery for 6G.
- Proposal 17 (Cross-frequency beam prediction): Study specification impacts concerning cross-frequency beam prediction including Inference, Monitoring and Data Collection operations.