OFDM vs. SC-FDMA for monostatic THz ISAC sensing under beam misalignment fading

Official URL: https://dx.doi.org/10.1109/SIU71813.2026.11636354

Terahertz (THz) integrated sensing and communication (ISAC) systems rely on highly directional beams that are sensitive to platform-induced misalignment. While beam misalignment (BM) fading models have been developed for THz channels, the impact of waveform selection on sensing performance under these conditions remains unclear. This paper compares OFDM and SC-FDMA for monostatic THz sensing at 0.85 THz with 20 GHz bandwidth, using a statistical BM fading model that distinguishes spot-filling and spot-limited target regimes. Monte Carlo simulations across several misalignment angles show that both waveforms achieve nearly identical range and velocity estimation accuracy. The performance gap between aligned and misaligned scenarios is substantial, while waveform choice has a negligible effect. These findings indicate that beam alignment is the critical design factor for THz ISAC, and waveform selection can be based on other system requirements.