Impact of Sinusoidal Co-channel CW Interference on the Spectral Efficiency of OTFS Modulation

The recently proposed Orthogonal Time Frequency Space (OTFS) modulation has been shown to be robust to mobility induced Doppler spread in next generation communication systems. Due to dense network deployment, next generation communication systems are expected to experience significant co-channel interference. Therefore, there is a need to study the robustness of OTFS modulation in the presence of co-channel interference. In this paper, we study the impact of sinusoidal co-channel continuous wave (CW) interference on the spectral efficiency (SE) of an Orthogonal Time Frequency Space (OTFS) modulation based communication system. In OTFS modulation, information symbols are embedded in the delay-Doppler (DD) domain. Analysis of the DD domain representation of the received CW interference shows that the interference received along a particular channel path is localized in a Doppler domain interval having width approximately twice the Doppler domain resolution (i.e., inverse of the OTFS frame time-duration). With fine Doppler domain resolution, the CW interference is localized to a small portion of the Doppler domain and is expected to interfere only with a small fraction of all information symbols. This observation is supported through simulations, where it is confirmed that the degradation in the OTFS SE performance is small when the Doppler domain resolution is fine.