  In this letter, we investigate error performance of rectangular pulse-shaped
orthogonal time frequency space (OTFS) modulation with a practical receiver.
Specifically, we consider an essential bandpass filter at receiver RF
front-end, which has been ignored in existing works. We analyse the effect of
rectangular pulses on practical OTFS receiver performance, and derive the exact
forms of interference in delay-Doppler (DD) domain. We demonstrate that the
transmitted information symbols in certain regions of the DD domain are
severely contaminated. As a result, there is an error floor in the receiver
error performance, which needs to be addressed for such OTFS waveform in
practical systems.
