Single Snapshot Based Carrier Frequency Offset Estimation for OCDMA

The orthogonal chirp division multiplexing (OCDM) is a recently proposed waveform for wireless communications. Due to its lower self-interference inherited from chirp modulation and robustness against multipath fading due to spreading, OCDM is suitable for integrated sensing and communication (ISAC) applications. However, similar to OFDM it could suffer from loss of orthogonality due to carrier frequency offset (CFO). In the literature, CFO estimation techniques for low latency highresolution applications have not yet been well investigated. In this paper, we propose a single snapshot based CFO estimation for OCDM and obtain its mathematical formulation. Further, we extend the proposed approach for orthogonal chirp division multiple access (OCDMA) transmission where reference signals of different users are multiplexed in a single OCDM symbol. To evaluate performance, the CFO estimation accuracy of the proposed approach is compared with the baseline time-correlation based approach. Results show that the proposed method outperforms the baseline approach while not relying on reference signal transmissions over multiple symbols. Furthermore, in the case of multi-user transmission, the accuracy of the proposed method remains stable whereas the baseline approach significantly suffers from inter-user interference.