Channel Estimation in Cross-Frame OTFS System With Ultra-High Mobility

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Abstract
In the upcoming next-generation wireless communication systems, high-mobility support serves as an essential part. OTFS (Orthogonal Time Frequency Space) modulation is regarded as a candidate waveform for 6G systems for its robustness in high mobility scenarios. However, its performance degrades when Doppler spreads beyond the subcarrier spacing with ultra-high speed, a condition referred to as the out-of-range Doppler (OD) channel. We analyze the input-output relationship under OD channels and reveal that the Delay-Doppler (DD) domain received signal is a superposition of the transmitted signal with an additional phase term. Based on this insight, we design a cross-frame OTFS framework for channel estimation, utilizing coprime subcarrier configurations to observe varying responses across subframes, and the out-of-range parameters are resolved using the Chinese Remainder Theorem (CRT). Furthermore, an effective channel estimation method is developed to handle multipath scenarios by decomposing subframes and matching response taps using fractional and amplitude information, which transforms the OD channel estimation problem into multiple single-domain problems by processing DD domain signals in layers. Simulation results demonstrate the effectiveness of the proposed method in estimating OD channels, outperforming existing approaches that fail under such conditions.
Funding Information
  • Natural Science Foundation of China (62361136810)
  • NSFC (62301455)
  • National Natural Science Foundation of China (U23A20274)

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