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The 6G waveform study tries to put many different industry proposals into one common frame. The purpose is to compare air-interface options in a consistent way. It also aims to guide the overall discussion so companies do not argue based on different assumptions. The study focuses on practical evaluation, so it looks at PAPR, BLER, out-of-band emissions, and how each waveform behaves under more realistic power-amplifier models. These metrics help the group understand not only theoretical performance but also behavior in real hardware, so the conclusions do not drift into unrealistic territory. Another important point is receiver complexity. The study keeps reminding that any candidate must be implementable with reasonable cost and power consumption. This is why the overall direction remains very pragmatic. The discussions also highlight deployment feasibility, because 6G should evolve from existing NR networks, not break away from them. So the recurring theme is to maintain a common waveform across multiple frequency ranges. This is considered one of the lessons learned from NR, so the group tends to favor the OFDM family and a smooth evolution of uplink single-carrier concepts. This allows dynamic operation without adding complexity just for the sake of change. The topic also emphasizes efficient initial access and robust cell search. These steps are critical for real-world usability, especially with wider bandwidths and more diverse deployment scenarios. Robustness under channel impairments, hardware non-idealities, and mobility conditions is given more weight than pure theoretical gains. Migration and coexistence are another part of the discussion, because 6G must work alongside existing systems during the transition period. However, sensing-specific waveforms are explicitly kept out of scope. The study keeps its focus on communication waveforms only, so sensing discussions do not distract from the main evaluation. Overall, the document tries to give the industry a stable baseline. It does this by organizing ideas, defining evaluation points, and narrowing down the practical directions so the RAN1 work can proceed smoothly.
Scope & AssumptionsThe scope of this study starts with a simple goal. It tries to define what the 6G waveform should achieve and what assumptions guide the evaluation. The main objective is to improve coverage and throughput in ways that remain deployment-feasible in real networks. This means the design must avoid unnecessary complexity at the receiver and must operate realistically across all relevant frequency ranges. The study also looks for unification, so the same basic waveform can work in FR1, FR2, and FR3 whenever possible. This allows dynamic operation while keeping the system simple enough to implement, so evolution from NR stays smooth and practical.
Common Evaluation AspectsThe study uses a common set of evaluation aspects so that every waveform candidate is compared on equal ground. It begins with PAPR and power-amplifier behavior, because both uplink and downlink depend heavily on how much back-off a waveform needs and how it behaves under realistic non-linear models with memory effects. It then looks at BLER and overall robustness by checking BLER versus SNR across representative channel models, Doppler conditions, and various impairments such as CFO, phase noise, and channel-estimation errors. The evaluation also includes out-of-band emissions, so the analysis measures spectral regrowth and ACLR under PA non-linearity and observes how windowing or filtering can shape the emission profile. Complexity and latency are treated with equal weight. The study considers FFT or filter sizes, the cost of equalization and tracking, and the resulting processing delay and memory footprint. The goal is to form a balanced view where performance, hardware behavior, and implementation feasibility are all assessed together.
Downlink Waveform (DL)The downlink waveform discussion starts from the CP-OFDM baseline because it already has a mature ecosystem and supports flexible numerology and multiplexing. This makes it the natural anchor point for 6G, even though it brings known challenges such as higher PAPR and sensitivity to CFO and phase noise. The study then looks at possible enhancements that stay within practical bounds. Windowed or filtered OFDM variants are considered to reduce out-of-band emissions without breaking compatibility. Coverage-related techniques such as power boosting for pilots or DMRS and OFDM-symbol repetition are explored as simple ways to extend reach in difficult conditions. The work also connects waveform behavior with system-level features like BWP-based multiplexing and carrier aggregation, so downlink operation can adapt dynamically without adding unnecessary complexity.
Uplink Waveform (UL)The uplink waveform discussion starts from DFT-s-OFDM because it naturally offers low PAPR, so it improves power-amplifier efficiency and uplink coverage. It also aligns well with the existing NR uplink processing chain, so it provides a smooth evolution path. From this baseline, the study looks at several enhancement options. Some proposals introduce additional low-PAPR techniques through improved sequence design or mapping so devices with limited power budgets can transmit more reliably. Other proposals target robustness in high-Doppler or phase-noise conditions, especially in FR3 and sub-THz bands where impairments become stronger. Trellis-Coded DFT-s-OFDM is explored as a way to improve maximum coupling loss and PA efficiency, while circularly pulse-shaped DFT-s-OFDM aims for better spectral containment without breaking the low-PAPR benefit. Hybrid modes that combine different transform-precoding approaches allow dynamic trade-offs between PAPR and throughput, so devices can adapt based on their power class and numerology. The study also considers AI-assisted pre-distortion and adaptive precoding to counter PA non-linearities in a more intelligent way. Joint waveform and channel-estimation designs are discussed for uplink reliability at higher frequencies, where estimation becomes more fragile. Finally, enhanced DFT-s-OFDM variants are evaluated for grant-free access and short-packet efficiency, which are important for low-overhead uplink operation in 6G.
Design Principles & Candidate CriteriaThe design principles for candidate waveforms stay tightly aligned with the study scope. The work focuses on the OFDM family because it already supports a unified structure across many scenarios and has proven flexibility through NR. This keeps the design consistent and avoids fragmentation across frequency ranges or use cases. Within this boundary, the group remains open to new waveform ideas, but only under strict conditions. Any proposal must show clear, deployment-relevant gains that go beyond what a natural OFDM evolution can achieve. The improvement must also hold under realistic assumptions, not just in ideal simulations. At the same time, the proposal must not raise UE complexity or power consumption in any meaningful way. This constraint reflects practical device realities and ensures that innovation does not come at the cost of viability. The overall goal is to advance performance while keeping the system simple enough to implement and scale in real networks.
Initial Access & Cell Search (waveform-related)The waveform study also looks at how initial access and cell search can be improved without adding unnecessary complexity. The goal is to design synchronization signals that remain easy to detect while supporting longer periodicities, since wider bandwidths and higher frequencies make frequent transmissions less efficient. This requires reliable detection even when the SSB appears less often or is transmitted under more challenging conditions. The study also examines ways to reduce the sync raster by lowering the SSB bandwidth or by adding more symbols to improve detection energy. These adjustments help devices find cells faster and with less scanning effort, so initial access becomes more robust and power-efficient across all frequency ranges.
Coexistence & Migration (waveform-level)The waveform-level coexistence and migration study focuses on how 6G can operate alongside NR without creating unnecessary signaling or resource conflicts. The main idea is to support MRSS in a way that reuses existing NR structures such as SSB or CSI-RS, and then apply rate-matching so the new signals do not collide with NR resource elements. This approach keeps the system simple and avoids redesigning well-established procedures. A key requirement is backward invisibility, meaning that NR UEs should not experience any disturbance or unexpected behavior when 6G signals share the same carrier. The study also considers semi-static sharing with NB-IoT or LTE-M when relevant, so legacy low-power devices can continue operating during the transition. The overall goal is to make coexistence predictable, low-overhead, and compatible with real deployment constraints.
Evaluation Scenarios & GuidanceThe evaluation scenarios are defined to guide how each waveform should be tested under conditions that reflect real deployment. The first scenario focuses on coverage-limited uplink operation, where devices face high maximum coupling loss and strict power-amplifier limits. In this case, low-PAPR behavior becomes essential because it directly affects uplink reach and reliability. The next scenario looks at wideband eMBB services that may use carriers in the 200300 MHz range, so PA behavior and out-of-band emissions must be evaluated carefully. These wide bandwidths also test how well a waveform supports agile multiplexing across large resource spans. A third scenario addresses FR3 operation and mobility stress. At these frequencies, phase noise and CFO sensitivity increase, so the waveform must tolerate stronger impairments. High-Doppler conditions are included as part of the baseline testing to make sure the candidates operate reliably in realistic mobility and propagation environments. The aim is to ensure that conclusions remain grounded and deployment-ready.
Metrics & Mitigation LeversThe study defines a clear set of metrics so every waveform can be compared consistently. The key items include PAPR, usually checked through CCDF at points like 0.01% or 0.1%, along with BLER versus SNR across representative channels. Spectral behavior is tracked through ACLR and out-of-band emission measurements, especially under realistic PA non-linearity. Implementation metrics such as compute load, processing latency, and memory footprint are evaluated in parallel so performance gains do not hide excessive complexity. Alongside these metrics, the study identifies several mitigation levers that can be applied when a waveform shows weaknesses. Power boosting is considered for improving link robustness, while CFO and phase-noise mitigation techniques help stabilize operation in higher-frequency ranges. OFDM-symbol repetition provides another simple way to enhance coverage, and BWP-level multiplexing helps adjust resource usage without needing major changes in the waveform itself. Together, these metrics and levers form a practical framework for guiding waveform evolution for 6G.
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