Joint Channel and AoA Estimation in OTFS System With Fractional Doppler Channels

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Abstract
Orthogonal time frequency space (OTFS) modulation is a promising technology for high-Doppler-effect mobile communication. However, fractional Doppler shifts cause inter Doppler interference, degrading the channel estimation (CE) performance, particularly at low signal-to-noise ratios (SNRs). Previous approaches have framed Doppler shift estimation as a direction-of-arrival problem but have limited accuracy because of the finite number of available Doppler points. To overcome this challenge, we propose a delay-staggered pilot scheme that leverages the abundant resources in the delay domain, effectively increasing the number of points for CE and enhancing its accuracy. Additionally, we introduce a novel angle-of-arrival estimation method tailored to the unique channel characteristics of OTFS modulation, reducing the antenna array requirements. Simulation results demonstrate that the proposed method achieves superior NMSE performance compared with existing approaches, including embedded pilot-based CE and grid evolution-based CE algorithms.
Funding Information
  • National Natural Science Foundation of China (62001171)
  • National Natural Science Foundation of Guangdong Province (2025A0505020094)
  • Open Research Fund of National Mobile Communications Research Laboratory
  • Southeast University (K202411)

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