R1-2509141
discussion
Overview of 6GR air interface
From MediaTek
Summary
This MediaTek contribution to RAN1#123 provides a comprehensive overview of technology directions for the 6G Radio (6GR) air interface, following up on RAN1#122bis discussions. It contains 48 numbered proposals and observations across sections covering scalable design, initial access, coverage, MRSS, spectrum aggregation, TN/NTN harmonization, and new areas like MIMO, device complexity, and sensing.
Position
MediaTek proposes focusing on scalable PHY design where common functionalities (basic PHY features, idle mode, initial access, DL/UL control, MRSS, coverage enhancements, energy saving) apply to all 6G device types, with adjustment allowed per device type. They argue against making early decisions on smallest device bandwidth envelope, requiring RAN1 to also consider non-BW complexity reduction techniques like 4ms processing time relaxation and half-duplex FDD operation, and to evaluate system impact of serving multiple bandwidth envelope devices simultaneously. They propose a unified DL channel information feedback mechanism (direct channel feedback) to replace iterative codebook enhancements, and require studying a single mobility RS distinct from SSB for all CONNECTED mode mobility functions to reduce resource overhead and UE complexity. They require investigating CSI-RS overhead reduction through time-domain periodicity increase supplemented by DMRS-based tracking and spatial/frequency domain compressed sensing, and propose a two-stage DCI design to reduce blind decoding complexity and PDCCH overhead. They propose studying an unconstrained native carrier switching framework with independent DL and UL carrier switching plus flexible UL-DL decoupling, and require striving for common and extendable TN/NTN designs from the start of 6G studies.
Key proposals
- Proposal 1 (Sec 2.1): The development of the scalable PHY design should consider that key parameters (Duplexing type, Antennas and RF chains, MIMO layer, Maximum Modulation order, Processing time, Maximum Tx output power, Maximum Bandwidth) may have different values for devices with different characteristics.
- Proposal 3 (Sec 2.1): For smallest maximum supported RF and BB UE BW, RAN1 to consider other complexity reduction techniques than BW reduction such as Processing time relaxation (up to 4ms), Half duplex operation in paired bands, and Peak rate reduction, plus system performance impacts of serving devices with different bandwidth envelopes in the same cell.
- Proposal (Sec 2.2): RAN1 to encourage RAN#110 to finalize agreement on minimum spectrum allocation, then evaluate whether a single narrowband design for initial access (Option 3) offers better system performance before considering puncturing or scalable design trade-offs.
- Proposal 1 (Sec 2.3): For 6GR sync signal design, consider harmonisation of TN and NTN deployments and Multi-TRP deployments including enabling reduced energy consumption for idle mode common signals/channels by SFNing them across multiple TRPs.
- Proposal 4 (Sec 2.3): Study a single mobility RS (quite different from NR SSB design) to support all mobility-related functions in CONNECTED mode, to minimize resource overhead, reduce UE power consumption/complexity/testing, and streamline mobility procedures.
- Proposal 1 (Sec 2.4): Frequencies around 7GHz, around 4GHz and around 700MHz should be considered for potential coverage improvement.
- Proposal 3 (Sec 2.5): Investigate how to reduce CORESET and (in a joint 5G/6G SDM scheduling scenario) DMRS overhead. Consider CORESET sharing and orthogonal/SDM'd DMRS between 5G/6G as potential solutions.
- Proposal (Sec 2.6): Multi-carrier design results in contiguous CA being more cumbersome and much less efficient than a single wider bandwidth from a system perspective is added to lessons learned from NR spectrum utilization.
- Proposal 1 (Sec 3.1): Focus on average/cell edge spectral efficiency, capacity and latency-bound capacity improvement rather than peak spectral efficiency.
- Proposal 2 (Sec 3.2): Investigate UE PHY procedural complexity at least for blind PDCCH decoding, UL control transmissions, spectrum aggregation/switching, BWP operation, MIMO and Mobility.
- Proposal 1 (Sec 3.3): Investigate time, spatial, and frequency domain approaches to reduce CSI-RS overhead, including both non-AI approaches and further optimizations via AI.
- Proposal 2 (Sec 3.3): Investigate feasibility of a unified and efficient DL channel information feedback mechanism to support a wide range of MIMO schemes, to avoid the need for later extensive CSI enhancements.
- Proposal 4 (Sec 3.3): Study improved low complexity MIMO approaches compared to 5G NR Rel-19.
- Proposal 2 (Sec 3.5): Study a simplified and efficient UCI reporting framework with design principles including minimizing arbitration among uplink channels, maximizing parallelism among uplink carriers, no PHY resource changes after scheduling an UL channel.
- Proposal 5 (Sec 3.7): Adopt missed detection probability, false alarm probability, estimation accuracy of range/location and Doppler/velocity, and resolution as metrics for sensing evaluation.