Approximation of Non-Ideal Filtering in OTFS via Variable Fractional Delay

The orthogonal time frequency space (OTFS) modulation is resilient to the Doppler effect and thus is employed in high-mobility communications. In earlier work, the equivalent representations of the OTFS transmission were established, revealing the profound impact of fractional delay on channel sparsity. However, these representations tend to be distorted and cumbersome when accounting for digital reception and non-ideal filtering. In this letter, we propose an alternative representation with low distortion that uses the variable-fractional-delay filter to characterize the fractional delays in a conventional digital transceiver. In our proposed method, the approximation of the received signal is improved, and the error performance is enhanced compared to the original approaches. At last, the simulations show that our proposed representation is valid.