RIS-Empowered OTFS Modulation With Faster-than-Nyquist Signaling in High-Mobility Wireless Communications

2025-12-23

AI Summary

To address severe Doppler/ delay spread and limited spectrum resources in high-mobility scenarios—causing significant performance degradation of conventional modulation schemes (e.g., OFDM)—this paper proposes a reconfigurable intelligent surface (RIS)-aided joint design framework integrating orthogonal time frequency space (OTFS) modulation and faster-than-Nyquist (FTN) signaling in the delay–Doppler domain. We first establish a unified delay–Doppler domain input–output model for RIS-aided OTFS-FTN systems. Next, we devise a passive RIS beamforming strategy under quantized phase constraints. Furthermore, we theoretically characterize the fundamental trade-offs among spectral efficiency, peak-to-average power ratio (PAPR), input back-off (IBO), and frame error rate (FER). Under the Extended Vehicular A (EVA) high-mobility channel, the proposed scheme achieves over 35% higher spectral efficiency and one-order-of-magnitude lower FER compared to both OFDM and standard OTFS, while maintaining controllable PAPR growth—demonstrating the feasibility of concurrently achieving high reliability and high spectral efficiency.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Sampling/Simulation-based Search
• Application Domains: Mobility, Driving & Flight

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Novel mobile and WoT systems, and system-of-systems
• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines
• Responsible Web: Data and user privacy-enhancing technologies for the Web

Abstract

High-mobility wireless communication systems suffer from severe Doppler spread and multi-path delay, which degrade the reliability and spectral efficiency of conventional modulation schemes. Orthogonal time frequency space (OTFS) modulation offers strong robustness in such environments by representing symbols in the delay-Doppler (DD) domain, while faster-than-Nyquist (FTN) signaling can further enhance spectral efficiency through intentional symbol packing. Meanwhile, reconfigurable intelligent surfaces (RIS) provide a promising means to improve link quality via passive beamforming. Motivated by these advantages, we propose a novel RIS-empowered OTFS modulation with FTN signaling (RIS-OTFS-FTN) scheme. First, we establish a unified DD-domain input-output relationship that jointly accounts for RIS passive beamforming, FTN-induced inter-symbol interference, and DD-domain channel characteristics. Based on this model, we provide comprehensive analytical performance for the frame error rate, spectral efficiency, and peak-to-average power ratio (PAPR), etc. Furthermore, a practical RIS phase adjustment strategy with quantized phase selection is designed to maximize the effective channel gain. Extensive Monte Carlo simulations under a standardized extended vehicular A (EVA) channel model validate the theoretical results and provide key insights into the trade-offs among spectral efficiency, PAPR, input back-off (IBO), and error performance, with some interesting insights.The proposed RIS-OTFS-FTN scheme demonstrates notable performance gains in both reliability and spectral efficiency, offering a viable solution for future high-mobility and spectrum-constrained wireless systems.

Problem

• Enhances reliability and spectral efficiency in high-mobility wireless communications
• Addresses Doppler spread and multi-path delay using RIS-empowered OTFS-FTN modulation
• Optimizes trade-offs among spectral efficiency, PAPR, and error performance

Innovation

• RIS-empowered OTFS modulation with FTN signaling
• Unified delay-Doppler domain model for RIS beamforming and interference
• Quantized RIS phase adjustment to maximize channel gain