Orthogonal Delay-Doppler Division Multiplexing with FMCW for ISAC

Orthogonal delay-Doppler (DD) division multiplexing (ODDM) modulation has recently been proposed as a promising paradigm for communications in doubly-selective channels. In this work, we propose a novel ODDM with frequency modulated continuous wave (FMCW) (ODDM-FMCW) signal to enable integrated sensing and communication (ISAC) with a low peak-to-average power ratio (PAPR). We first propose the DD-domain embedded root-raised-cosine filtered FMCW (DD-RRC-FMCW) signal, where digital chirp compression is introduced for efficient radar signal processing. By superimposing this signal onto an ODDM data frame, we obtain the ODDM-FMCW signal for the proposed ISAC system. Next, we introduce a modified orthogonal matching pursuit algorithm for data-aided sensing. The algorithm is then combined with the soft successive interference cancellation with minimum mean square error detector to perform joint channel estimation and data detection. Our numerical results show that the proposed ODDM-FMCW signal delivers excellent normalized mean square error and bit error rate performance for ISAC.