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Low-Complexity Channel Estimation in OTFS Systems with Fractional Effects

Guangyu Lei, Yanduo Qiao, Tianhao Liang, Weijie Yuan, Tingting Zhang

TL;DR

This work tackles OTFS channel estimation under fractional delay and Doppler effects, which spread energy and cause inter-path interference in the Delay-Doppler domain. It introduces a low-complexity, sequential path estimation method that leverages energy leakage to rank paths by fractional severity and then iteratively reconstructs and subtracts path contributions without iterations. By extracting $P_{\max}$ strong DDRE taps, performing MLE-based delay and Doppler estimation with template responses, and applying energy-leakage-driven IPI elimination, the approach achieves accurate $\hat{\tau}_p$, $\hat{\nu}_p$, and $\hat{\alpha}_p$ with reduced complexity. Experimental results show NMSE and sensing MSE improving with PSNR and path leakage handling, validating the method for real-time ISAC applications in high-mobility scenarios.

Abstract

Orthogonal Time Frequency Space (OTFS) modulation exploits the sparsity of Delay-Doppler domain channels, making it highly effective in high-mobility scenarios. Its accurate channel estimation supports integrated sensing and communication (ISAC) systems. The letter introduces a low-complexity technique for estimating delay and Doppler shifts under fractional effects, while addressing inter-path interference. The method employs a sequential estimation process combined with interference elimination based on energy leakage, ensuring accurate channel estimation. Furthermore, the estimated channel parameters can signifcantly improve ISAC system performance by enhancing sensing capabilities. Experimental results validate the effectiveness of this approach in achieving accurate channel estimation and facilitating sensing tasks for ISAC systems.

Low-Complexity Channel Estimation in OTFS Systems with Fractional Effects

TL;DR

This work tackles OTFS channel estimation under fractional delay and Doppler effects, which spread energy and cause inter-path interference in the Delay-Doppler domain. It introduces a low-complexity, sequential path estimation method that leverages energy leakage to rank paths by fractional severity and then iteratively reconstructs and subtracts path contributions without iterations. By extracting strong DDRE taps, performing MLE-based delay and Doppler estimation with template responses, and applying energy-leakage-driven IPI elimination, the approach achieves accurate , , and with reduced complexity. Experimental results show NMSE and sensing MSE improving with PSNR and path leakage handling, validating the method for real-time ISAC applications in high-mobility scenarios.

Abstract

Orthogonal Time Frequency Space (OTFS) modulation exploits the sparsity of Delay-Doppler domain channels, making it highly effective in high-mobility scenarios. Its accurate channel estimation supports integrated sensing and communication (ISAC) systems. The letter introduces a low-complexity technique for estimating delay and Doppler shifts under fractional effects, while addressing inter-path interference. The method employs a sequential estimation process combined with interference elimination based on energy leakage, ensuring accurate channel estimation. Furthermore, the estimated channel parameters can signifcantly improve ISAC system performance by enhancing sensing capabilities. Experimental results validate the effectiveness of this approach in achieving accurate channel estimation and facilitating sensing tasks for ISAC systems.
Paper Structure (11 sections, 11 equations, 3 figures, 1 table, 2 algorithms)

This paper contains 11 sections, 11 equations, 3 figures, 1 table, 2 algorithms.

Table of Contents

  1. Introduction
  2. System Model
  3. Proposed algorithm
  4. Extraction of Path Information
  5. Low-complexity Estimation Algorithm
  6. Sequential Estimation and IPI Elimination
  7. The Complexity Analysis of Proposed Algorithm
  8. Numerial Results
  9. Simulation Setup
  10. Results discussion
  11. Conclusion

Figures (3)

  • Figure 1: Schematic illustration of OTFS communication assists sensing, where different reflectors' states lead to different channel situations. (a) The channel state when there are two paths with the same delay. (b) The channel state when there are two paths with the same Doppler.
  • Figure 2: Schematic representation of the decomposition of the channel state on the DDRE. (a) Channel response on the DDRE. (b) Corresponding Doppler response and delayed response of the path. (c) The real delay response versus the simulated response calculated by the proposed algorithm. (d) The real Doppler response versus the simulated response calculated by the proposed algorithm.
  • Figure 3: (a) NMSE performance of the proposed algorithm as a function of pilot SNR. (b) MSE of estimated Doppler as a function of pilot SNR. (c) MSE of estimated delay as a function of pilot SNR. (d) MSE of estimated Channel gain as a function of pilot SNR. (e) SER performance of the proposed method in comparison with other methods.