Oversampled Receiver for Coded OTFS With Different D/A Reconstruction Filters

This letter analyzes a coded OTFS system with different digital-to-analog (D/A) reconstruction filters and an oversampling receiver in the presence of fractional delay and Doppler. In such a setting, we present the input-output relation for a generic D/A reconstruction filter. Then we present the low complexity delay time (DT) maximal ratio combining (MRC) detection with receiver oversampling for coded OTFS with turbo iteration. Further, we focus on two D/A reconstruction filters for OTFS: Sinc and root raised cosine (RRC) and we provide, for the first time, a fair comparison of their performance in terms of bandwidth expansion, spectral efficiency, and out-of-band (OOB) radiation. For this, we fix the spectral efficiency for all cases by tuning the code rate and the roll-off factor. Under the same spectral efficiency, we conclude that the Sinc filter outperforms the RRC filter in terms of error performance and bandwidth requirement for both oversampling and Nyquist rate sampling receivers.