On the Orthogonal Coexistence of AFDM and OFDM for Joint Sensing and Communication

In this paper, we propose a coexistence scheme based on orthogonal frequency division multiplexing (OFDM) and affine frequency division multiplexing (AFDM) to enable efficient joint sensing and communication (JSAC) under different channel conditions. Specifically, the distinct signal representations of both waveforms in the frequency and affine domains are exploited to ensure, by construction, the orthogonality and flexibility of the proposed mechanism within a shared resource grid. Furthermore, a novel pilot design is introduced to enable joint channel estimation for both communication and sensing tasks in a unified and coherent manner, using a single pilot structure for both functionalities. To further enhance the scheme's adaptability, the proposed approach dynamically adapts to channel mobility and time variation, ensuring seamless and stable operation in JSAC networks across practical scenarios. Numerical results validate the effectiveness of the design, demonstrating accurate, low-complexity radar parameter estimation while simultaneously maintaining high data rates, and reducing the peak-to-average-power ratio (PAPR) when compared with the conventional OFDM and AFDM baselines. Taken together, these elements indicate that the proposed coexistence strategy achieves sensing capability and communication efficiency within a single design while preserving the intended orthogonality and flexibility.