Practical low complexity MRC detector for OTFS with oversampling receiver

The recently proposed orthogonal time-frequency space (OTFS) waveform has shown superior performance in high-mobility environments when compared to orthogonal frequency division multiplexing (OFDM). In this paper, we propose a low complexity maximal ratio combining (MRC) detection for an over-sampled OTFS receiver to handle channels with fractional delay and Doppler shifts. Specifically, we first derive an input-output relation in the delay-Doppler domain. Then we present a modified iterative MRC detection taking advantage of over-sampled received signal to improve the error performance. Its complexity is equivalent to that of the standard MRC detection scaled by the oversampling factor, while remains much lower than the standard message passing (MP) detection. Simulation results show that the proposed detection for receiver oversampling outperforms not only the conventional MRC detection for receiver Nyquist sampling but also the MP detection for receiver oversampling.