R1-2601847
discussion
On Uplink WUS and corresponding operation
From Nokia
Nokia's prior position on
10.6.2
at
RAN1#124
· AI-synthesized, paraphrased
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Proposes postponing the UL WUS and operation study on A.I. 10.6.2 to avoid duplication with the foundational PRACH and RACH procedure study on A.I. 10.5.1.2. Presents a technical case that the current stage lacks clarity on what key complements UL WUS signal provides over PRACH preamble design, whether sufficient performance gain exists in coverage or energy efficiency to justify the extra design effort, and what use cases UL WUS operation covers that RACH procedure cannot. For the feasibility aspect, opposes dedicated low-power radio (LPR) receiver architecture for UL WUS at the base station, instead requiring that the UL WUS signal type be identical to other uplink signals so that common network hardware and the common radio modem at the BS side can be reused with functionalities implemented simply by a subset of existing hardware components.
Summary
This Nokia Tdoc addresses the design, feasibility, and deployment scenarios for Uplink Wake-up Signal (UL WUS) in 6G. It provides 18 proposals and 8 observations, covering signal design for different RRC states, BS receiver feasibility, and detailed operational analysis across standalone and multi-cell/carrier deployment scenarios.
Position
Nokia proposes that the UL WUS signal type should reuse existing uplink signals: PRACH preamble for RRC Idle/Inactive UEs and existing uplink signals/channels (SRS, UL DMRS, SR, PUCCH, PUSCH) for RRC Connected UEs. They argue against a dedicated low-power BS receiver module for UL WUS, stating none is foreseen for 6G BS hardware, and require that the UL WUS signal utilize the common radio modem to minimize operational cost. Nokia questions the feasibility of DS#1a due to the unresolved issue of UL WUS transmit power determination without DL pathloss estimation from PSS/SSS, and requires confirmation from spectrum regulations on whether a UE can transmit without first receiving DL synchronization signals. They propose studying a UL WUS framework that allows UEs to conditionally reuse stored system information to avoid redundant MIB/SIB1 acquisition, and support studying on-demand reference signals triggered by UL WUS for SCell operations and cell switch mobility.
Key proposals
- Proposal 1 (Sec 2): For UE in RRC connected state, the uplink signals and channels (i.e. SRS, UL DMRS, SR, PUCCH, PUSCH, etc.) shall be considered for UE on-demand requesting in uplink.
- Proposal 2 (Sec 2): For UE in RRC Idle/Inactive state, the uplink PRACH preamble shall be considered for UE on-demand requesting in uplink.
- Proposal 4 (Sec 4.1.1): Whether the UE is allowed to transmit UL WUS signal to a cell without first receiving DL synchronization signals in licensed spectrum needs to be confirmed based on spectrum regulations.
- Proposal 5 (Sec 4.1.2): DS#1b is applied to the UE in RRC Idle/Inactive state.
- Proposal 6 (Sec 4.1.2): For a standalone cell initially with PSS/SSS transmission only, the UE may further on-demand request MIB information as well as SIB1 information based on UL WUS signal.
- Proposal 9 (Sec 4.1.3): DS#1c can be applied to UEs either in RRC Connected state or in Idle/Inactive state, depending on the detailed scenarios to be discussed.
- Proposal 10 (Sec 4.1.3): For DS#1c, RAN1 shall align between A.I. 10.6.2 and A.I. 10.5.5 to avoid discussion overlapping and striving for a common design for UE requesting for uplink resources.
- Proposal 11 (Sec 4.1.3): For DS#1c, UE on-demand request of transmission periodicity adaptation of synchronization signals, PBCH, or SIB1 for the energy saving standalone cell could be interesting to be studied.
- Proposal 12 (Sec 4.2.1): RAN1 to check and clarify whether the UE is allowed to transmit UL WUS signal to a cell without first receiving the DL synchronization signals from that cell, based on licensed spectrum regulations.
- Proposal 13 (Sec 4.2.1): For 6GR design with SS/PBCH-less SCell operation, it is proposed to consider more flexible and scalable solutions that can fit in with different deployment scenarios.
- Proposal 14 (Sec 4.2.1): For DS#2a with multi-carrier scenario, it is proposed to study the SS/PBCH-less SCell operation for UE in RRC Connected state.
- Proposal 15 (Sec 4.2.2): For DS#2b, it is proposed to study and develop a UL WUS framework that enables a UE in RRC Idle/Inactive state to avoid redundant MIB/SIB1 acquisition when the system information remains unchanged and conditionally reuse stored system information.
- Proposal 16 (Sec 4.2.2): RAN1 to study the on-demand reference signal for DS#2b with multi-carrier scenario, which may benefit to reduce the latency for UE synchronization or beam management for UE in RRC connected state.
- Proposal 17 (Sec 4.2.3): RAN1 to investigate the joint operation of on-demand reference signal with cell switch operations, where the UE may request on-demand reference signal transmissions from the neighboring cell for the purpose of faster mobility measurements.
- Proposal 18 (Sec 4.2.3): RAN1 to study the on-demand reference signal before SCell cell#2 (pre-)configuration that may benefit to reduce the latency for the measurement of SCell addition.