A Sequence Spread Modulation Scheme Based on Orthogonal Time Frequency Space

Future networks will need to support more usage scenarios, including higher speed scenarios and ultra-reliability scenarios for which the current waveforms are not suitable. Recently, the proposed orthogonal time frequency space (OTFS) modulation proves to be robust to Doppler spead, but it uses a conventional linear receiver which is susceptible to multipath channel gains and has high complexity. In this paper, we propose a sequence spread modulation scheme to improve system reliability. The proposed scheme spreads symbols to the Doppler domain before OTFS modulation. At the receiver, we develop a Rake receiver over the Doppler domain. Simulation results show that the performance of the proposed sequence modulation scheme is almost independent of the channel multipath gains compared to a conventional linear receiver based on OTFS, which means the performance of the proposed receiver is always close to the best performance of a linear receiver.