OCDM-Based FMCW Waveform Design for FSO Integrated Sensing and Communications

The integrated sensing and communication (ISAC) is emerging as a crucial technology due to its reduced hardware costs and broad application scenarios, where the free space optics (FSO) based ISAC can potentially support both wide- bandwidth communication and high-accuracy ranging. However, the majority of the FSO ISAC designs in the literature can only achieve low data-rate communications. In order to simultaneously transmit high-quality communication data and high-accuracy ranging information using a single FSO waveform, in this paper, we propose an integrated waveform design that combines orthogonal chirp division multiplexing (OCDM) with frequency modulated continuous wave (FMCW) light detection and ranging (LiDAR). To elaborate, one subcarrier from OCDM is selected as the FMCW ranging at the LiDAR receiver, while the remaining OCDM subcarriers can be used to enhance communication data rate. Experiments demonstrate the feasibility of our proposed scheme, centimeter-level ranging accuracy is achieved, with acceptable error vector magnitude (EVM) performance, while simultaneously achieving a communication rate of 3.182 Gbps.