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The study on 6G modulation begins with a simple baseline. 5G NR’s uniform QAM set is the anchor, so the group keeps the familiar DL range from BPSK to 1024-QAM. UL follows the NR rule as well, so p/2-BPSK for DFT-s-OFDM and QPSK to 256-QAM stay as the default. This gives a stable starting point, and it avoids unnecessary disruption. From this anchor, the group explores higher orders such as 4096-QAM for downlink and 1024-QAM for uplink. These are examined only when the scenario makes sense. LoS and FWA are the typical examples, because SNR, EVM and hardware constraints become manageable in those conditions, so the study can stay realistic. Constellation shaping is another major branch. Both probabilistic and geometric shaping are included, so the scope covers NUC (1D/2D) and PAS-type variants. A common evaluation plan is required, so all proposals are tested under realistic propagation and MIMO assumptions. Metrics such as BLER, capacity, PAPR, MPR, and implementation complexity must be checked in a unified way, so comparison becomes fair. RAN4 is involved early, because feasibility depends on actual RF constraints and not just theoretical gains. Several companies try to lower UL PAPR/MPR with improved DFT-s-OFDM, but many members recommend moving these ideas to the waveform track, so the modulation study stays clean and focused. Overall, the direction is evolutionary. NR modulation is the baseline. Shaping and very-high-order QAM are studied only when they give targeted system gains. Any proposal must show clear benefits at system level before increasing implementation burden.
Baseline & scopeThe baseline for the 6G modulation study stays simple. NR’s uniform QAM set is the anchor, so the group starts from the same DL and UL ranges used in 5G NR. DL keeps QPSK up to 1024-QAM, and UL keeps p/2-BPSK for DFT-s-OFDM together with QPSK up to 256-QAM. This gives a stable foundation, so the study can focus on realistic extensions instead of rebuilding the entire modulation family. Very-high-order options such as 4096-QAM for downlink and 1024-QAM for uplink remain in scope, but they are examined only when the scenario truly justifies them. LoS-type conditions or FWA deployments are typical examples, because hardware limits, SNR and EVM requirements become realistic in those cases. Another key point is scoping discipline. Many companies propose UL PAPR/MPR reduction, but most members prefer to treat these under the waveform agenda. This separation keeps the modulation track clean, so decisions can focus on constellation behavior rather than PA-related waveform engineering.
High-order modulation applicabilityHigh-order modulation is treated as a scenario-dependent option. The group does not aim for universal deployment. Instead, very-high-order schemes like 4096-QAM on the downlink and 1024-QAM on the uplink are considered only when the propagation and hardware environment can support them. LoS and FWA cases are the typical reference, because these conditions give predictable SNR and tighter EVM control, so the hardware burden stays within reach. Even in these favorable settings, the study requires strong system-level evidence. Any proposal must show clear throughput or spectral-efficiency gains that justify the added implementation cost. Complexity, memory, PA constraints and receiver processing load must all be evaluated together, so the decision reflects real deployment conditions rather than isolated link-level benefits.
Constellation shapingConstellation shaping is a major study item and covers both probabilistic and geometric approaches. The scope includes PAS(Probabilistic Amplitude Shaping)-type schemes on the probabilistic side and NUC(Non-Uniform Constellation)-style shaping on the geometric side, so both 1D and 2D variants remain under evaluation. This broad coverage allows the group to compare gains across multiple shaping families without locking into one technique too early. Implementation awareness is critical throughout the study. Mapper design, LLR computation, and storage requirements must be tracked carefully, because these elements directly affect hardware cost and memory footprint. Rate-matching interactions also need close attention, since shaping changes symbol distributions and can influence effective throughput. The group keeps these constraints visible from the start, so shaping decisions reflect not only theoretical benefits but also real modem-level feasibility.
Common evaluation frameworkThe study requires a unified evaluation campaign, so every proposal is tested under the same conditions. Channel models must be consistent, and MIMO assumptions must match across companies. This avoids fragmented results and makes BLER and capacity comparisons meaningful. All candidates are judged against identical performance targets, so the evaluation reflects true relative gains rather than differences in simulation setup. The metric set is also fixed early. BLER or FER performance, spectral efficiency, and PAPR/MPR behavior form the core. Complexity and memory usage are included as mandatory items, because shaping and higher-order schemes often increase implementation load. SNR and EVM budgets must be tracked carefully, since feasibility depends on real RF constraints. Early coordination with RAN4 is essential for this part, so the study stays aligned with hardware capabilities and does not drift into unrealistic parameter ranges.
Uplink considerationsUplink discussions focus heavily on PAPR and MPR behavior, because these factors dominate UE power efficiency. The study continues to explore relief options around DFT-s-OFDM, but the group also tries to clarify where this work belongs. Many members prefer to keep PAPR/MPR topics in the waveform track, so modulation decisions can stay focused on constellation behavior rather than PA engineering. This separation prevents ambiguity when comparing proposals. Practical constraints remain strict on the uplink. Any choice of higher-order modulation or constellation shaping must respect UE PA limits and the power-class definitions. Efficiency drops quickly when PAPR rises, so the study requires careful analysis of how each technique interacts with the hardware envelope. UL proposals are evaluated with these real-world constraints at the front, so gains remain deployable rather than purely theoretical.
Process & coordinationThe overall process follows an evolutionary path. NR modulation is kept as the default anchor, so the study begins from a stable and widely deployed baseline. Enhancements are considered only when there is strong supporting evidence, so the group avoids unnecessary complexity. Any candidate must show measurable gains under realistic assumptions, and alignment across working groups is required before moving forward. Coordination with RAN4 is especially important. Shaping proposals and very-high-order modulation options need early feedback from RF and EVM perspectives, because feasibility depends on real hardware margins. Early RAN4 interaction also clarifies PAPR and PA-related constraints, so the study does not advance techniques that exceed RF limits. This coordinated process keeps the modulation track grounded in deployable performance rather than theoretical gains alone.
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