Study Highlights Why OTFS Outperforms OFDM in Doubly-Dispersive Channels

Table of Links

• I. Abstract and Introduction
• II. Related Work
• III. Modeling of Mobile Channels
• IV. Channel Discretization
• V. Channel Interpolation and Extrapolation
• VI. Numerical Evaluations
• VII. Conclusions, Appendix, and References

VII. CONCLUSIONS

In this paper, we talked about the advantages of OTFS over OFDM in terms of spectral efficiency, resulting from the much reduced channel training overhead. We showed that the D-D domain channel model is also an approximation of the real channel, but it is more accurate then the LTI model, and thus allows us to estimate the channel with a much reduced channel estimation frequency. The predictability of the channel in T-F domain comes from the sparsity of response in D-D domain. Besides, we showed that it’s possible to use a very small amount of resources for channel interpolation. A pipeline algorithm is proposed for channel interpolation with reduced processing delay. Further more, we showed that channel extrapolation and data-aided channel tracking would be possible, benefiting from the predictability of the D-D domain channel. Two sources of channel interpolation error are unveiled: the D-D domain aliasing resulting from the finite TF window, and the ISCI induced by channel dispersion. Their impacts on channel estimation error are quantified. Overall, we can conclude that OTFS has a huge advantage over OFDM due to the reduced channel training overhead. As a matter of fact, this advantage actually comes from the D-D domain channel model itself, and is thus shared by other signaling techniques designed for doubly-dispersive channels.

APPENDIX A SUM OF sinc AND DIRICHLET FUNCTIONS

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