Conclusions and future directions

In this chapter, we summarize the key advantages of delay-Doppler modulation and list the pros and cons of the OTFS variants. The pros and cons are compared in terms of transmit power, detection complexity, and normalized spectral efficiency that takes into account the pilot overhead required for channel estimation. The comparison is useful for readers to choose the right OTFS variant for their specific design requirements. Finally, we present a number of research directions of interest to the research community working on OTFS.