R1-2601866
discussion
Discussion on uplink transmission scheme(s) for uplink channels
From ZTE
Summary
This ZTE contribution on 6G uplink design contains 35 proposals and 8 observations, addressing enhancements to PUSCH, PUCCH, DMRS, and multi-TRP operation. The document prioritizes coverage enhancement, coherent transmission, flexible codeword-to-layer mapping, high-resolution codebooks, unified DMRS patterns based on Comb-3 with FD-OCC=4, and supports asymmetric DL/UL TRP decoupling from 6G day 1.
Position
ZTE proposes prioritizing uplink coverage enhancement for 6G at around 7 GHz through coherent transmission, advanced UL codebook design including high-resolution and frequency-selective codebooks, and mandatory increased UE transmit power of 26 dBm or more. They propose studying flexible codeword-to-layer mapping with three options (CW per layer, single CW with individual modulation order, two CWs with {1,1}/{1,2}/{2,2} mappings) to address observed per-layer SINR disparity exceeding 6 dB in field tests and simulations under the Rel-19 handheld UT model. They require a unified and streamlined DMRS design with Comb-3 CDM groups and FD-OCC=4 as the basic pattern, extending to Comb-6 across double-RB with TD-OCC=2 for up to 48 orthogonal ports, while proposing to deprioritize SIP and postpone DMRS-free studies until channel modulation outcomes are reached. ZTE proposes PUCCH simplification to two formats (sequence-based format A for 1-6 bits, format B for larger payloads with comb-based DMRS), and requires support for asymmetric DL sTRP/UL mTRP decoupling from day 1 with multi-TRP operation from initial access.
Key proposals
- Proposal 1-1-1 (Sec 1): 6G uplink design should prioritize coverage enhancement, especially for spectrum around 7 GHz, and uplink capacity expansion to support uplink-intensive traffic types.
- Proposal 1-2-4 (Sec 2): To ensure adequate 6G uplink coverage, prioritize coherent transmission and advanced UL codebook design.
- Proposal 2-2 (Sec 3): The following BS antenna configurations at around 7 GHz are prioritized for PUSCH evaluation: 128 TXRUs, 768 AEs and 256 TXRUs, 1536 AEs.
- Proposal 3-1-1 (Sec 4.1): For 6G PDSCH/PUSCH codeword-to-layer mapping, even for up to 4 layer transmission, flexible CW-to-layer mapping and MCS assignment should be fully studied with UT model.
- Proposal 3-2-5 (Sec 4.2.2): A new port‑selection codebook should be supported, targeting scenarios such as low‑capability UEs and practical handheld UEs with non‑uniform antenna arrays.
- Proposal 3-3-1 (Sec 4.3): For PUSCH single slot scheduling, a unified resource mapping is pursued with flexible start symbol S={0, 1, ..., 13} and PUSCH length L = {1, 2, ..., 14}, i.e. merge NR PUSCH mapping Type A and B.
- Proposal 3-4-2 (Sec 4.4): For UL resource allocation, frequency-domain interleaving within UE allocated PUSCH should be studied in 6G.
- Proposal 3-5-1 (Sec 4.5): In order to achieve intra-cluster interference randomization, dynamic scrambling ID update, e.g., along with TCI update, should be supported.
- Proposal 4-3-2 (Sec 5.3): 6GR should target at least 2 PUCCH formats: PUCCH format A for small payload size, e.g., 1-6 bits sequence based PUCCH; PUCCH format B focusing on UCI transmission capacity and coverage.
- Proposal 5-2-2 (Sec 6.2.2): Comb-3 CDM groups with FD-OCC length = 4 per RB per symbol is assumed as the basic DMRS pattern, and its streamlined extension by comb-6 CDM groups with FD-OCC length = 4 across double-RB and TD-OCC length = 2 across double-symbol can be used to facilitate up to 48 orthogonal DMRS ports.
- Proposal 5-3-1 (Sec 6.3.1): Depriortize the study on SIP at the beginning of 6GR.
- Proposal 5-3-2 (Sec 6.3.2): Postpone the study on DMRS-free at the beginning of 6GR, e.g., at least till the outcome of channel modulation for 6GR is reached.
- Proposal 6-1-1 (Sec 7): To improve uplink transmission performance, especially for cell-edge UEs, multi-TRP operation should be considered for 6G deployment: CJR (targeting for FR1/around-7GHz) and NCJR transmission (targeting FR2/around 30GHz).
- Proposal 6-1-2 (Sec 7): Support the new architecture of DL-TRP and UL-TRP decoupling, i.e., asymmetric DL sTRP/ UL mTRP, in 6G day 1.