FUTUREWEI · 10.5.2.2

Futurewei proposes a UE-centric DMRS adaptation framework where the UE reports minimum DMRS density requirements (D_F, D_T, D_J) rather than selecting preferred patterns, achieving over 70% reporting overhead reduction compared to direct pattern index reporting. For hybrid antenna architectures in UMB, Futurewei proposes distinguishing two MU-MIMO transmission cases: when full CSI is available, adjusting both analog beams (subject to phase-only constraints) and digital precoders; when only analog-beam-specific CSI is available, adjusting only digital precoders without modifying analog beams. Futurewei presents a technical case for per-subcarrier matched-filter precoding that simultaneously achieves finest precoding granularity and wideband channel estimation, collapsing the effective channel impulse response to one dominant zero-lag tap. For TDD cooperative MIMO, Futurewei proposes DL interference probing via aperiodic SRS where the network configures UEs to transmit SRS with parameters tied to associated PDSCH transmissions (PRB allocation, port allocation), enabling distributed inter-cell interference nulling without inter-gNB information exchange.

Futurewei proposes adopting the existing 5G NR MIMO/RS/CSI framework as a 6G baseline while requiring AI/ML integration from day-1 of the MIMO framework design. The company proposes a UE-assisted DMRS pattern selection scheme where UEs report minimum DMRS density requirements (D_F, D_T, D_J) rather than preferred patterns, claiming over 70% reporting overhead reduction compared to direct pattern reporting. Futurewei proposes studying per-subcarrier matched-filter frequency-selective precoding that simultaneously achieves finest precoding granularity and single wideband channel estimation, addressing what they identify as a fundamental limitation of 5G NR subband precoding. The document proposes cooperative MIMO schemes leveraging TDD reciprocity with DL interference probing via SRS, presenting capacity gains of 64.8% in Dense Urban and 26.9% in Urban Macro scenarios with 45Mbps XR traffic. Futurewei emphasizes hybrid antenna architectures for UMB with large antenna element counts (2048) and moderate TXRU numbers, distinguishing them from fully-digital architectures based on subarray size and dynamic analog beamforming adjustability.