Spreadtrum · 10.5.2.2
Downlink transmission scheme(s) for downlink shared channels ·
RAN1#124bis · Source verification
the AI's delta
strengthened
vs RAN1#124
Spreadtrum hardened their complexity-minimization stance on two fronts. First, they added an explicit requirement for a single PDSCH mapping type to reduce receiver complexity,' elevating a general preference for simplicity to a specific design constraint. Second, they strengthened their argument against multiple transmission schemes by adding a commercialization precedent: only Rel-15 schemes achieved good commercialization while later enhanced schemes were not implemented.' Their DMRS port support expanded from preserving NR port counts to proposing up to 32 ports via increased CDM groups or longer FD-OCC, a concrete upward revision. Their technical case against SIP is refined from insufficiently evaluated for multi-user interference and standardization impact to quantified AI complexity concerns (1.48M parameters, 80M FLOPs). The MRSS position hardened: previously opposing SDM between NR and 6G,' now explicitly opposes signals/channels sharing between NR and 6G in addition to SDM opposition. The layer mapping rule is newly specified: first half layers map to CW0 and remaining to CW1' with single MCS per codeword, adding implementation detail absent from the prior meeting.
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Contributions at RAN1#124bis · 1 doc
Discussion on downlink transmission scheme(s) for downlink shared channels for 6GR
Position extracted by AI
Spreadtrum proposes maintaining 5G NR layer limits (max 8 layers, 2 codewords) and a baseline layer mapping rule where the first half layers map to CW0 and remaining to CW1, with a single MCS per codeword. They require a single PDSCH mapping type to reduce receiver complexity and oppose multiple transmission schemes for the same scenario, arguing that only Rel-15 schemes achieved good commercialization while later enhanced schemes were not implemented. For DMRS, they propose defining a single DMRS type for DL and supporting up to 32 ports via increased CDM groups or longer FD-OCC, and present technical case against SIP (superimposed pilot) by deprioritizing its study due to insufficient demonstrated gains and increased AI model complexity requiring 1.48M parameters and 80M FLOPs. For MRSS, they oppose signals/channels sharing between NR and 6G as well as SDM between the two RATs, and propose semi-static FDM/TDM and rate matching of 6GR PDSCH around NR signals/channels.
Summary
Spreadtrum presents a comprehensive analysis of downlink transmission schemes for 6G, containing 21 proposals and 5 observations covering PDSCH design, DMRS, PTRS, and MRSS aspects. The document argues for simplifying 6G designs relative to 5G NR by unifying schemes, minimizing configurations, and avoiding marginal enhancements.
Prior contributions at RAN1#124 · 1 doc · Feb 09, 2026
Discussion on downlink transmission scheme(s) for downlink shared channels for 6GR
Position extracted by AI
Spreadtrum proposes unified 6GR downlink transmission schemes to minimize UE and NW implementation complexity, explicitly opposing multiple schemes for the same scenario and scheme enhancements yielding less than 10% performance gain. They retain NR baselines for maximum layers (8), maximum codewords (2), DMRS port count, and PN sequence for CP-OFDM, while requiring a single DMRS type for both DL and UL. For AI/ML, they present simulation results showing AI-based channel estimation achieving similar BLER with reduced DMRS overhead (2-symbol DMRS matching 3-symbol non-AI performance in time domain, 1/3 RE reduction in frequency domain) and propose prioritizing sparse orthogonal DMRS (sub-case A) over superimposed pilots (SIP), which they consider insufficiently evaluated for multi-user interference and standardization impact. For NR-6GR MRSS, they propose semi-static FDM/TDM and rate matching mechanisms while opposing SDM between NR and 6GR due to negative performance impacts.
Summary
This Spreadtrum contribution provides 15 proposals and 5 observations on 6G downlink transmission schemes, codeword-to-layer mapping, DMRS design, and MRSS aspects. The company advocates for unified transmission schemes to minimize complexity, specifies DMRS overhead reduction using AI/ML receivers, and proposes baseline NR-reusing design principles with conservative enhancements only for significant performance gains.
How this was derived
The AI extracted the "position extracted" field above directly from each Tdoc during summarization.
For the delta summary at the top, the AI compared Spreadtrum's consolidated stance at RAN1#124bis
against their stance at RAN1#124 and classified the change as
strengthened.
Always verify critical claims against the original Tdocs linked above.