Diversity Analysis of OTFS Over Block Time-Varying Channels

• Published in: IEEE transactions on vehicular technology Vol. 73; no. 9; pp. 14062 - 14067
• Main Authors: Bora, Amit Sravan, Phan, Khoa T., Hong, Yi
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-09-2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analytical models; Block time-varying channel; Channels; Delays; Discrete Fourier transforms; diversity; Error analysis; OTFS; pairwise error probability; Performance prediction; Symbols; Time-frequency analysis; Time-varying channels; Vectors
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2024.3396490

Orthogonal time frequency space (OTFS) modulation exhibits excellent performance in time-varying channels with severe Doppler shifts. Diversity analysis is an effective method in predicting error performance of an OTFS system. Recent works have studied OTFS diversity in a time-varying channel assuming constant delay-Doppler (DD) channel realization per frame. However, in practice, DD channel realizations may vary in a frame due to the rapid changes in channel geometry relative to a frame duration, leading to a block time-varying (BTV) channel. This paper analyzes the OTFS diversity in such BTV channels. Specifically, we derive the pairwise error probability of the system and analyze its diversity by finding the minimum rank of the pairwise error matrix and its associated multiplicity. We also compare it with other known schemes and demonstrate its improved diversity. Finally, simulations are performed to validate the analytical results.