Key Technologies of FD

Full-DuplexFull-duplex technology, by enabling simultaneous transmission and reception in the same frequency band, not only enhances communication capacity but also eliminates the sensing blind spots inherent in conventional TDD. This dual advantage positions FD as a pivotal breakthrough for advancing ISAC system performance. This chapter introduces FD technology within the ISAC framework, focusing on the FD system model, FD self-interference (SI) signal model, and interference cancellation techniques. Initially, we overview the FD system model, exploring echo signal characteristics to ensure synchronous signal transmission and reception within the same frequency band. This synchronization supports the seamless integration of communication and sensing, laying a foundation for FD-ISAC systems. We then summarize methods for modeling FD-ISAC system self-interference, considering nonlinearities from wireless multipath channels and transceiver links. The model includes direct path leakage, reflected interference, and hardware-induced distortions, providing an accurate reflection of real-world interference characteristics and a basis for interference mitigation strategies. Finally, we detail self-interference cancellation techniques across spatial, analog, and digital domains. Spatially, advanced antenna designs and beamforming suppress interference. Analog solutions involve high-linearity amplifiers and optimized front-end designs to minimize leakage, while digital strategies use adaptive algorithms and machine learning to enhance cancellation precision. This multi-tiered approach ensures efficient interference management in complex environments, optimizing both communication and sensing functionalities in FD-ISAC systems.