FUTUREWEI · 10.5.3.2

Futurewei proposes that hybrid antenna architectures with large antenna element counts and moderate TXRU counts be a key focus for UMB base stations, specifically defining hybrid beamforming as a combination of adjustable analog beamforming (via phase shifters) and digital precoding. They propose studying simultaneous multi-beam codebooks that allow multiple orthogonal beams per OFDM symbol to reduce full CSI acquisition latency—for example, enabling 128 RF chains driving 2048 elements to acquire full CSI in 16 OFDM symbols instead of 2048. They present quantitative performance results for cooperative MIMO via downlink interference probing (BiT), showing capacity improvements from ~8 to ~13.1 UEs in Dense Urban and from ~5.2 to ~6.6 UEs in Urban Macro for 45Mbps XR traffic with [DDDUU] slot configuration, and propose SRS trigger enhancements that associate SRS transmission parameters with PRB/port allocation of corresponding PDSCH. They propose extending 5G SRS carrier-based switching into a general UL switching framework that eliminates switching-back by moving all transmissions to the switching-to carrier, and additionally propose enabling UL signals as QCL source RS for DL TCI states.

Futurewei proposes that 5G NR MIMO/RS/CSI framework serves as the starting point for 6G with enhancements focused on upper midband (UMB) support, general SE/UPT performance, and fast FR2 beam acquisition. They propose integrating AI/ML as part of the 6G MIMO framework from day-1, urging RAN1 to discuss high-level MIMO framework principles enabling AI/ML-based functionality and identifying AI/ML use cases to facilitate assessment. For UMB base stations, they propose hybrid antenna architecture as a key focus area for panels with >512 elements or ≥100 MHz bandwidth, specifying particular antenna combinations to study (2048 elements with 256 TXRUs at 7 GHz; 2048 elements with 32 or 128 TXRUs at 15 GHz) and proposing enhanced SRS repetition schemes for fast full CSI acquisition to support efficient MU-MIMO. They propose a general carrier switching framework that reduces/eliminates switching-back by moving all transmissions to the switching-to carrier and maintaining one set of signals/channels over n carriers, potentially combined with DL carrier switching. They propose studying cooperative MIMO via DL interference probing based on SRS enhancements, presenting simulation results showing capacity gains of 64.8% in dense urban and 26.9% in urban macro scenarios for 45Mbps XR traffic. They propose QCL/TCI enhancements to enable UL signals such as SRS as QCL source RS for DL TCI states.