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

TL;DR

This paper introduces novel low-complexity tone injection schemes for PAPR reduction in OFDM and AFDM systems, utilizing candidate ranking and depth-first search to improve performance without increasing computational complexity.

Contribution

The proposed TI schemes are the first to iteratively update candidates via ranking guided by local peaks, achieving over 1 dB PAPR gain with complexity comparable to FFT-based methods.

Findings

Achieve over 1 dB PAPR reduction compared to baseline schemes.

Maintain complexity similar to FFT, enabling practical implementation.

Consistent performance improvement across various subcarrier counts.

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.