Joint Channel and CFO Estimation for Chirped-OFDM-Based ISAC

To address the performance degradation induced by inter-carrier interference (ICI) in multicarrier ISAC systems and investigate the sensing characteristics of chirped-OFDM waveforms, this paper proposes a chirped-OFDM-based ISAC framework. By strategically performing sensing prior to demodulation, the approach circumvents the ICI-induced distortions. The sensing task is then formulated as a joint estimation of channel parameters and carrier frequency offset (CFO), for which the modified Cramér-Rao lower bound and maximum likelihood estimator are derived. The CFO in chirped-OFDM helps improve sensing accuracy, while the obtained estimates facilitate low-complexity frequency synchronization. Simulation results validate that the proposed framework offers sensing accuracy comparable or superior to interference-free OFDM models, and illustrate the effects of chirp rate and time-frequency configuration on sensing performance.