A Novel Delay-Doppler-Based Channel Estimation Method in Doubly-Dispersive OCDM Systems

Orthogonal chirp division multiplexing (OCDM) has recently emerged as a new candidate for the 6G waveform. In high-mobility wireless channels, the inseparability of the data symbols in both time and frequency domains makes channel estimation in OCDM-based wireless communication quite challenging. In this letter, we address this issue by investigating the representation of the OCDM waveform in the delay-Doppler domain in which we reveal that OCDM carriers exhibit a sparse representation. Building upon this observation, we propose a low-complexity channel estimation technique for OCDM systems. This technique involves designing pilots in the Fresnel domain and estimating the channel in the delay-Doppler domain. We evaluate the performance of the proposed channel estimation and demonstrate the superior performance of our approach, showcasing both high accuracy and low computational complexity.