Narrowband Interference Cancellation Using a Fine Frequency Shift in Single-Carrier Frequency Domain Equalization (SC-FDE) Systems

This paper proposes a narrowband interference (NBI) cancellation technique for single-carrier frequency domain equalization (SC-FDE) systems. SC-FDE is a transmission scheme commonly used in mobile communication uplinks or low-Earth-orbit (LEO) satellite communications due to its low peak-to-average power ratio (PAPR) characteristics. In the presence of narrowband interference, removing the interference is crucial, as SC-FDE systems are vulnerable to the interference. A straightforward approach to interference removal is frequency nulling, which can be easily implemented using FFT (Fast Fourier Transform). However, this method is only effective when the interference frequency coincides with specific FFT grid frequencies. To address this limitation, this paper proposes identifying the interference frequency, applying a fine frequency shift, and then canceling or nulling the interference. After that, the fine frequency is shifted back for reception. By aligning the interference frequency with an FFT grid frequency, the proposed technique enables simple and effective narrowband interference cancellation. The performance of the proposed method is validated through computer simulations, which demonstrate excellent interference cancellation performance regardless of the signal-to-interference ratio (SIR).