6G    

 

 

 

TDoc Tracking - Waveform

The 6G waveform study consolidates industry inputs into a common frame for comparing air-interface options and guiding discussion. It focuses on practical evaluation—looking at PAPR, BLER, out-of-band emissions, and behavior under more realistic power-amplifier models—while emphasizing pragmatic receiver complexity and deployment feasibility. A recurring theme is maintaining a common waveform across frequency ranges, leveraging NR experience by favoring the OFDM family (with uplink single-carrier evolution) and enabling dynamic operation without unnecessary complexity. This topic stresses efficient initial access and cell search, robust performance in real-world conditions, and coexistence/migration considerations; sensing-specific waveforms are explicitly out of scope for this study.

Scope & Assumptions

  • Objectives for the waveform
    • Improve coverage and throughput with deployment-feasible solutions.
    • Favor pragmatic receiver complexity and realistic operation across bands.
  • Unification across ranges
    • Seek a common design usable in FR1/FR2/FR3 where feasible.
    • Enable dynamic operation without unnecessary complexity.

Common Evaluation Aspects

  • PAPR & PA behavior
    • Assess CCDF and required PA back-off for UL/DL candidates.
    • Model non-linearities and memory effects with realistic PAs.
  • BLER & robustness
    • Evaluate BLER vs SNR under representative channels and Doppler.
    • Test sensitivity to CFO, phase noise, and channel-estimation errors.
  • OOBE & spectral compliance
    • Measure spectral regrowth/ACLR under PA non-linearity.
    • Consider effects of windowing/filtering on emissions.
  • Complexity & latency
    • Account for FFT/filter sizes, equalization/tracking cost.
    • Track processing latency and memory footprint.

Downlink Waveform (DL)

  • CP-OFDM baseline
    • Mature ecosystem; flexible numerology and multiplexing.
    • Challenges: higher PAPR; CFO/phase-noise sensitivity.
  • DL enhancements
    • Windowed/filtered OFDM variants to reduce OOBE (Out of Band Emission).
    • Power boosting (e.g., pilots/DMRS) and OFDM-symbol repetition for coverage.
    • BWP-level multiplexing and CA strategies coordinated with waveform behavior.

Uplink Waveform (UL)

  • DFT-s-OFDM baseline
    • Low PAPR improves PA efficiency and uplink coverage.
    • Aligns with existing NR UL processing chain.
  • UL enhancements
    • Additional low-PAPR techniques (sequence design/mapping).
    • Robustness improvements for high Doppler/phase-noise regimes.

Design Principles & Candidate Criteria

  • OFDM-family focus
    • Only OFDM-based waveforms considered per study scope.
    • Unified design across scenarios/use cases is preferred.
  • Admitting new waveforms
    • Require clear, deployment-relevant gains beyond OFDM evolution.
    • Must not materially increase UE complexity/power consumption.

Initial Access & Cell Search (waveform-related)

  • Efficient synchronization signals
    • Support longer periodicities while maintaining reliable detection.
    • Reduce sync raster by lowering SSB bandwidth and/or adding symbols.

Coexistence & Migration (waveform-level)

  • MRSS with NR
    • Signal sharing (e.g., reuse NR SSB/CSI-RS) and rate-matching to avoid RE collisions.
    • Ensure backward “invisibility” to NR UEs; enable semi-static sharing with NB-IoT/LTE-M where applicable.

Evaluation Scenarios & Guidance

  • Coverage-limited UL
    • Dimension for high MCL and realistic PA constraints.
    • Favor low-PAPR UL behavior for extended coverage.
  • Wideband eMBB
    • Evaluate 200–400 MHz carriers with PA/OOBE implications.
    • Check multiplexing agility under wide bandwidths.
  • FR3 & mobility stress
    • Account for higher phase-noise/CFO sensitivity.
    • Include high-Doppler conditions in waveform testing.

Metrics & Mitigation Levers

  • Key metrics
    • PAPR (CCDF at 0.01%/0.1%), BLER vs SNR, ACLR/OOBE.
    • Compute/latency/memory as implementation metrics.
  • Mitigation levers
    • Power boosting; CFO/phase-noise mitigation techniques.
    • OFDM symbol repetition; BWP-level multiplexing options.

Reference