rch directions through which the available literature on OTFS can be extended. In all the available literature that was explained above, rectangular transmit and receive windows are considered for OTFS. This is while the transmit and receive windows can be designed to improve, for instance, PAPR, channel estimation, and signal detection performance of OTFS. All the available literature on OTFS considers perfect synchronization in both time and frequency domain while this is not the case in practical systems. Hence, timing and fre- quency offset estimation and compensation in both single and multiuser scenarios need to be studied for OTFS. Most of the literature on OTFS is based on OFDM for time-frequency transmission and the performance of OTFS when waveforms other than OFDM are utilized is unknown to date. This is another important line of research that requires attention in the near future. The study of OTFS in massive MIMO channels is still in its infancy and some issues such as pilot contamination problem of massive MIMO when OTFS is deployed for data trans- mission is unknown. Even though there is some literature available on channel equalization and detection of OTFS, channel equalization and multiuser detection in the uplink of OTFS in both OMA and NOMA modes need further study and analysis. Dynamic resource allocation plays a pivotal role in interference reduction and opti- mization of resource utilization in multiuser vehicular communication systems. Thus, resource allocation is another aspect of OTFS that needs to be studied in the future. References 1 Wang, T., Proakis, J.G., Masry, E., and Zeidler, J.R. (2006). Performance degradation of OFDM systems due to Doppler spreading. IEEE Transactions on Wireless Communica- tions 5 (6): 1422-1432. doi: https://doi.org/10.1109/TWC.2006.1638663. 2 Farhang-Boroujeny, B. (2014). Filter bank multicarrier modulation: a waveform candi- date for 5G and beyond. Advances in Electrical Engineering 2014. 25p. 3 Dean, T., Chowdhury, M., and Goldsmith, A. (2017). A new mod