OTFS Performance over Fractional Delay-Doppler Channel Under Nakagami-m Fading

Orthogonal time frequency space (OTFS) modulation represents data in the delay-Doppler (DD) domain. However, certain challenges in OTFS remain less explored, such as the impact of fractional DD taps, which introduce inter-Doppler and inter-delay interference (IDI), degrading system performance. Additionally, scattering in the DD domain can lead to overlapping taps, resulting in the Doppler squint effect. In this paper, we investigate the effects of fractional DD on single-input-single-output (SISO) and multiple-input-multiple-output (MIMO) OTFS systems under Nakagami-m fading, a generalized fading model. We also analyze the Doppler squint effect and its impact on system performance. Our study provides a detailed performance analysis through theoretical derivations and simulations, considering variations in system parameters such as fading characteristics, antenna configurations, and both fractional and integer DD values.