R1-2509114
discussion
Views on 6G energy efficiency
From Apple
Summary
This document analyzes 5G NR energy-saving features for both UE and network, identifying deployment shortfalls and backward-compatibility limitations. It presents 26 proposals and 6 observations to guide the design of 6G energy efficiency, covering evaluation models, common signal/channel design, and time/frequency domain enhancements.
Position
Apple proposes that 6G NES features must be well-justified against UE impact, citing that 5G UE power-saving features remain under-deployed due to late standardization and lack of network incentive. It supports Cat 2 BS power model as the realistic baseline, arguing Cat 1 model overestimates NES gain, and proposes updated PDSCH/PDCCH UE power scaling rules (PDSCH: 0.5+0.5*(X-20)/80; PDCCH: 0.9+0.1*(X-20)/80 for X up to 100MHz). It proposes a dual-SSB concept (always-on Type-1 for RRC_IDLE UEs and on-demand Type-2 for RRC_CONNECTED UEs) and clustered PRACH/Paging resources near SSB bursts to achieve native NES. For time-domain adaptation, Apple requires a simplified/harmonized design merging C-DRX, DCP, PDCCH skipping, SSSG switching, and LP-WUS, and proposes a two-level WUS (cell WUS + UE WUS) for joint cell DTX/DRX and C-DRX operation while opposing cell DTX/DRX for IDLE/INACTIVE UEs given clustered common signal design.
Key proposals
- Proposal 1 (Sec 2.2): 6G NES features should be well justified considering impact to UE.
- Proposal 3 (Sec 3.1): Support Cat 2 BS power model as the baseline BS power model for 6G NES evaluation. If one unified BS power model cannot be achieved, Cat 1 BS power model can be optionally considered.
- Proposal 5 (Sec 3.2): Reuse the power values for different power states in TR 38.840.
- Proposal 10 (Sec 4.1.1): For SSB, study to introduce two types of SSBs, one is an always-on signal and designed for RRC_IDLE UEs and the other is on-demand SSB for RRC_CONNECTED UEs as well as during the transition from IDLE to CONNECTED.
- Proposal 12 (Sec 4.1.2): For SIB1 delivery, periodic broadcast of SIB1 is supported. Study and evaluate OD-SIB1 delivery in both multi-cell and single-cell cases, considering how much additional NES gain can be obtained through SIB1 reduction under the assumption of increased SSB periodicity.
- Proposal 13 (Sec 4.1.3): For PRACH design, consider PRACH resource configuration to provide clustered common signal/channel transmission/reception to achieve native NES while taking into account of UE random access latency.
- Proposal 14 (Sec 4.1.4): For Paging configuration/adaptation, consider more systematic design to provide clustered Paging Occasions or Paging Frames close to SSB burst for NES, together with enough synchronization signals before POs for UE power saving.
- Proposal 15 (Sec 4.2.1): Time domain adaptation techniques for PDCCH monitoring, including C-DRX, Rel-16 DCP, PDCCH skipping, SSSG switching, and LP-WUS, should be considered together for a simplified/harmonized design.
- Proposal 17 (Sec 4.2.2.1): Consider support of cell DTX/DRX for CONNECTED UEs not configured with C-DRX, i.e., when cell DTX/DRX is configured, PDCCH monitoring, CSI measurement and RRM/RLM measurement behaviors follow the configured cell DTX/DRX pattern.
- Proposal 21 (Sec 4.2.2.1): Study a two-level WUS for joint operation of cell DTX/DRX and C-DRX, where a cell WUS is used to indicate the wake-up of a next cell DTX/DRX active period, and a UE WUS is used to indicate the wake-up of a next C-DRX cycle for a particular UE in the cell DTX/DRX active period.
- Proposal 22 (Sec 4.2.2.2): Considering the proposals that PRACH and Paging resources can be configured close to SSB burst to form a clustered pattern, there is no need to support cell DTX/DRX for IDLE/INACTIVE operation.
- Proposal 24 (Sec 4.4.1): Study simplified UE bandwidth adaptation for UE power saving, considering at least a minimum set of bandwidth-dependent configuration parameters, and same numerology across different bandwidth configurations.
- Proposal 26 (Sec 4.5): Study UE-initiated adaptation based on e.g. UE knowledge of traffic and RF condition, including which configuration adaptation can be triggered by a UE and the corresponding procedures.