R1-2600147
discussion
Downlink transmission scheme(s) for downlink control channels
From Huawei
Summary
This document presents Huawei's views on 6GR downlink control channel design, outlining 5 observations on current NR PDCCH limitations and 14 proposals for 6GR study directions. The proposals span performance metrics, CORESET structure, transmission schemes, MU-MIMO, DMRS design, and a two-stage DCI framework to address PDCCH capacity and UE power consumption challenges.
Position
Huawei proposes retaining the NR CORESET concept and basic one-port DMRS-based transmission schemes as the 6GR baseline while studying specific enhancements. They propose decoupling the maximum PDCCH bandwidth from PDSCH bandwidth to reduce UE power consumption, and studying appropriate CORESET time duration variations for TDD slots with asymmetric DL/UL grant loads. Huawei proposes studying PDCCH MU-MIMO to increase capacity, and requires study of PDCCH DMRS inter-cell/inter-UE interference mitigation mechanisms, citing cross-correlation problems with short sequence lengths under NR pseudo-random sequence initialization. They propose a two-stage DCI framework where the 1st-stage DCI has a fixed compact format scheduling the 2nd-stage DCI, which carries DL/UL scheduling information without requiring blind detection effort.
Key proposals
- Proposal 1 (Sec 5): Control channel blocking probability, throughput, BLER, and UE power consumption need to be evaluated for 6GR control channels.
- Proposal 2 (Sec 5): The concept of CORESET, that provides a time-frequency resources for PDCCH, could be retained as the basis for 6GR.
- Proposal 3 (Sec 5): 6GR studies appropriate CORESET bandwidth and/or time duration considering UE power saving while guaranteeing system performance such as PDCCH blocking probability, scheduling flexibility, and scheduling delay, and matching different DCI quantities in TDD slots.
- Proposal 6 (Sec 5): The following 5G NR transmission schemes for control channel could be retained as the basis for 6GR: one-port transmission with sub-band or wideband precoder, and channel estimation based on DMRS.
- Proposal 9 (Sec 5): 6GR should study PDCCH MU-MIMO.
- Proposal 10 (Sec 5): 6GR should study the PDCCH DMRS inter-cell/inter-UE interference mitigation mechanism for efficient support of increased PDCCH capacity.
- Proposal 4 (Sec 5): UE power saving while guaranteeing system performance such as PDCCH blocking probability, scheduling flexibility, and scheduling delay, etc.
- Proposal 5 (Sec 5): Matching the different DCI quantities in slots carrying DL grant only and slot carrying both DL/UL grants in the case of TDD.
- Proposal 7 (Sec 5): One-port transmission with sub-band or wideband precoder.
- Proposal 8 (Sec 5): Channel estimation based on DMRS.
- Proposal 11 (Sec 5): RAN1 should study two-stage DCI for L1 DL control information.
- Proposal 12 (Sec 5): The 1st-stage DCI provides the information scheduling the 2nd-stage DCI.
- Proposal 13 (Sec 5): The 2nd-stage DCI provides the information for DL and UL scheduling.
- Proposal 14 (Sec 5): Downlink transmission schemes and channel structure for the 2nd-stage DCI could be further studied in 6GR.