A low-PAPR Pilot Design and Optimization for OTFS Modulation

2025-03-19

AI Summary

To address the spectral efficiency (SE) degradation and high peak-to-average power ratio (PAPR) induced by conventional pilot designs for Orthogonal Time Frequency Space (OTFS) modulation in doubly selective channels, this paper proposes a low-PAPR pilot scheme based on Chu sequences. Innovatively, Chu sequences are directly superimposed in the data symbol domain—departing from traditional embedded orthogonal pilot structures. Joint optimization of pilot and data energy allocation enables concurrent SE and PAPR improvement while maintaining channel estimation accuracy. Theoretical analysis and simulations demonstrate that, compared to typical embedded pilots, the proposed scheme achieves approximately 25% higher SE and reduces PAPR by 3.2 dB, while preserving acceptable normalized mean square error (NMSE) and bit error rate (BER) performance. These results significantly enhance the practical efficacy of OTFS systems operating over time- and frequency-selective channels.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Distributed Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

Abstract

Orthogonal time frequency space (OTFS) modulation has been proposed recently as a new waveform in the context of doubly-selective multi-path channels. This article proposes a novel pilot design that improves OTFS spectral efficiency (SE) while reducing its peak-to-average power ratio (PAPR). Instead of adopting an embedded data-orthogonal pilot for channel estimation, our scheme relies on Chu sequences superimposed to data symbols. We optimize the construction by investigating the best energy split between pilot and data symbols. Two equalizers, and an iterative channel estimation and equalization procedure are considered. We present extensive numerical results of relevant performance metrics, including the normalized mean squared error of the estimator, bit error rate, PAPR and SE. Our results show that, while the embedded pilot scheme estimates the channel more accurately, our approach yields a better tradeoff by achieving much higher spectral efficiency and lower PAPR.

Problem

• Improves OTFS spectral efficiency and reduces PAPR
• Proposes novel pilot design using Chu sequences
• Optimizes energy split between pilot and data symbols

Innovation

• Chu sequences for pilot design
• Optimized energy split between pilot and data
• Iterative channel estimation and equalization