Pilot Chirp-Assisted OCDM Communications Over Time-Varying Channels

Orthogonal chirp division multiplexing (OCDM) has been proposed as a novel modulation scheme to take advantage of its double-spreading feature in both the time and frequency domains. It shows more resilient against different impairments. However, it is mainly investigated under time-invariant channels. In this letter, we propose a channel estimation method based on pilot chirps for OCDM transmissions under time-varying multipath channels. Relying on a basis expansion model (BEM), the impact of OCDM modulation and demodulation on time-varying multipath channels is thoroughly analyzed. Furthermore, the pilot chirp-assisted OCDM (pca-OCDM) is designed to minimize the minimum mean square error (MMSE) of the proposed MMSE channel estimator. The proposed channel estimation approach is compared with the state-of-the-art and demonstrates superior performance.