Linear Precoding Design for OTFS Systems in Time/Frequency Selective Fading Channels

• Published in: IEEE wireless communications letters Vol. 14; no. 3; pp. 816 - 820
• Main Authors: Ge, Yao, Meng, Lingsheng, G., David Gonzalez, Wen, Miaowen, Guan, Yong Liang, Fan, Pingzhi
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.03.2025; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Channels; Demodulation; Diversity gain; Doppler effect; Error analysis; Fading channels; linear precoding; Modulation; Number theory; OFDM; OTFS; PEP analysis; Precoding; Receivers; Selective fading; Time-frequency analysis; time/frequency selective fading channels; Transforms; Transmitters; Wireless communications
• ISSN: 2162-2337; 2162-2345
• DOI: 10.1109/LWC.2024.3524459

Even orthogonal time frequency space (OTFS) has been shown as a promising modulation scheme for high mobility doubly-selective fading channels, its attainability of full diversity order in either time or frequency selective fading channels has not been clarified. By performing pairwise error probability (PEP) analysis, we observe that the original OTFS system can not always guarantee full exploitation of the embedded diversity in either time or frequency selective fading channels. To address this issue and further improve system performance, this letter proposes linear precoding solutions based on algebraic number theory for OTFS systems over time and frequency selective fading channels, respectively. The proposed linear precoded OTFS systems can guarantee the maximal diversity and potential coding gains in time/frequency selective fading channels without any transmission rate loss and do not require the channel state information (CSI) at the transmitter. Simulation results are finally provided to illustrate the superiority of our proposed precoded OTFS over both the original unprecoded and the existing phase rotation OTFS systems in time/frequency selective fading channels.