Time Domain NOMA-Inspired ISAC Waveform Design

To enhance spectral efficiency in Integrated Sensing and Communication (ISAC) systems, this paper proposes a Non-Orthogonal Multiple Access (NOMA)-inspired waveform that superimposes a quantized Frequency-Modulated Continuous Wave (FMCW) sensing signal and an Orthogonal Frequency Division Multiplexing (OFDM) communication signal in the time domain. Compared to frequency-domain integration schemes, this approach offers computational simplicity and the potential for lower processing latency, while utilizing a time domain Successive Interference Cancellation (SIC) receiver to separate the signals. The communication Bit Error Rate (BER) and sensing performance, evaluated by the Receiver Operating Characteristic (ROC) curve, are analyzed. Results confirm a flexible trade-off between the dual functions, demonstrating that with sufficient quantization levels (M), the sensing performance can closely approach that of a dedicated FMCW radar. These findings validate the proposed time-domain superposition as a practical framework for future ISAC systems.