Low-Complexity Tone Injection via Candidate Ranking for PAPR Reduction in OFDM and AFDM Systems

2026-04-20

AI Summary

This work addresses the challenge of achieving both low computational complexity and effective peak-to-average power ratio (PAPR) suppression in tone injection (TI) schemes for OFDM and AFDM systems. The authors propose a novel candidate-ranking mechanism guided by time-domain local peaks, integrated with iterative TI sequence updates and depth-first search to optimize the tree-based search process. For the first time, candidate ranking and depth-first search are incorporated into the TI framework, enabling significant PAPR reduction while maintaining FFT-level computational complexity. Experimental results demonstrate that the proposed method achieves over 1 dB PAPR gain compared to existing TI approaches across various subcarrier configurations, offering a superior trade-off between performance and complexity, along with strong system compatibility and generality.

Technology Category

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

Application Category

• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines
• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Security and Privacy: Privacy-enhancing technologies

Abstract

Tone injection (TI) is a promising distortionless PAPR reduction technique that incurs no spectral efficiency loss. However, state-of-the-art TI schemes based on random candidate generation or clipping noise spectrum suffer from fundamental limitations in PAPR performance. In this paper, we propose novel TI schemes compatible with both OFDM and AFDM systems. The proposed schemes iteratively update the TI sequence via a candidate ranking procedure guided by time-domain local peaks. This accurately selects effective candidates while achieving a complexity comparable to that of the fast Fourier transform. Depth-first search is further integrated to enhance PAPR performance by exploiting the tree structure of the process. Simulations demonstrate that the proposed schemes achieve over 1 dB PAPR gain over baseline TI schemes at comparable complexity. The gain is consistent across various numbers of subcarriers under controlled per-iteration complexities, confirming a superior performance-complexity trade-off for both OFDM and AFDM.

Problem

• PAPR reduction
• Tone Injection
• OFDM
• AFDM
• peak-to-average power ratio

Innovation

• Tone Injection
• PAPR Reduction
• Candidate Ranking
• Depth-first Search
• Low Complexity