R1-2508642
discussion
Views on Energy Efficiency for 6GR
From AT&T
Summary
AT&T presents 15 proposals and 12 observations on Energy Efficiency (EE) for the 6G Radio (6GR) interface, arguing that EE should be a Day-1 mandatory design objective rather than an afterthought. The document covers five key technical areas: an overarching EE framework, initial access SSB adaptation, cell DTX/DRX unification, spatial-domain adaptation with high-resolution precoding, and evaluation methodology/metrics.
Position
AT&T requires energy efficiency to be a Day-1 mandatory 6GR objective and proposes a bottom-up single-RAT design scaling from minimum KPIs upward to the most demanding use cases. For initial access, they propose studying three SSB adaptation alternatives: always-on periodicity adaptation (40/80/160ms), always-on adaptation with micro-repetition, and always-on adaptation combined with on-demand SSB, citing that extending SSB periodicity beyond 20ms enables significant network energy savings via longer deep sleep periods. For cell DTX/DRX, they propose evaluating a unified EE framework that encapsulates NR cell DTX/DRX and C-DRX functionalities and studying expansion of signals/channels subject to cell DTX configuration. For spatial-domain adaptation, they propose studying a DFT-based precoding framework where a larger precoder for a full port set can straightforwardly derive orthonormal sub-precoders for port subsets, noting the specific technical challenge that sub-selecting rows of a DFT matrix does not yield an orthonormal matrix by default. For evaluation methodology, they propose an aggregate throughput normalized by total system power metric, including power consumed by RF circuits, local oscillators, filters, amplifiers, and ADC/DAC modules.
Key proposals
- Proposal 1 (Sec 2.1): Energy efficiency is leveraged as a main 6GR objective and supported as a Day-1 mandatory feature.
- Proposal 6 (Sec 2.2): At least the following alternatives for SSB adaptation procedures are considered for 6GR study: Alt-1: Always-on SSB periodicity adaptation (40/80/160ms); Alt-2: Always-on SSB periodicity adaptation with micro-repetition; Alt-3: Always-on SSB periodicity adaptation in conjunction with on-demand SSB.
- Proposal 7 (Sec 2.3): Evaluate the steps needed to derive a unified EE framework that encapsulates the NR cell DTX/DRX and C-DRX functionalities for 6GR interface.
- Proposal 10 (Sec 2.4): For 6GR interface, study the feasibility of deriving a DFT-based precoding framework in which a precoder associated with a set of ports can be straightforwardly used to derive an orthonormal sub-precoder associated with a subset of the set of ports.
- Proposal 12 (Sec 2.5): An energy efficiency metric based on aggregate throughput normalized by the total system power at the transmitter and/or receiver side, including power needed to operate different transmitter/receiver modules, is considered as a starting point for evaluation of energy efficiency in 6GR air interface.
- Proposal 15 (Sec 3): RAN1 chair guidance is needed on integrating the outcome of the energy efficiency study with the new 6GR study agendas planned to debut in RAN1#124, as well as ensure that proposed approaches for study in these agendas consider energy efficiency evaluation metrics at both the network and UE sides.
- Proposal 2 (Sec 2.1): Strive for 6GR interface design that achieves energy savings at both the network side and the UE side.
- Proposal 3 (Sec 2.1): Metric(s) that ensure energy saving mechanisms at the NW side have no detrimental impact on the UE side, and vice versa, are introduced in the RAN WG1 study of EE in 6GR interface.
- Proposal 4 (Sec 2.1): Energy efficiency enhancement approaches are considered for all supported RRC states in 6GR.
- Proposal 5 (Sec 2.1): 6G Radio is designed bottom-up, i.e., a single RAT is scaled from a minimum set of KPIs, where resources are allocated upwards to the most demanding use cases, to deliver network energy savings across verticals featuring different device types.
- Proposal 8 (Sec 2.3): Study the feasibility of expanding the set of signals/channels abiding to the cell DTX configuration, where the system performance, complexity and energy efficiency are considered as metrics for the study.
- Proposal 9 (Sec 2.4): For 6GR interface, evaluate the tradeoff between performance, energy efficiency, UE complexity and CSI feedback overhead focusing on scenarios with high-resolution DL precoding configured.
- Proposal 11 (Sec 2.5): Energy Efficiency metric(s) are included as 6GR key performance metrics from day 1.
- Proposal 13 (Sec 2.5): Study idle mode energy efficiency metrics for UE EE, network EE, and joint UE and NW EE.
- Proposal 14 (Sec 2.5): Study relevant baseline schemes for network and UE energy efficiency assessment, including NW and UE configurations, network load(s), and frequency ranges. Note: Strive to simplify the evaluation assumptions whenever applicable for a given scenario.