A Novel Method of Removing the Influence of Continuous Electromagnetic Wave Disturbances in OFDM Systems

Abstract

This article describes a novel technique for removing the influence of a continuous wave (or narrowband) electromagnetic disturbance in orthogonal frequency division multiplexing (OFDM) systems with quadrature amplitude modulation or phase-shift keying modulation schemes. The technique relies on a mathematical derivation of how a continuous wave electromagnetic disturbance induces spectral leakage in the OFDM system. Using this derivation, an algorithm is obtained that aims to cancel the continuous wave electromagnetic disturbance by estimating its frequency, retrieving its amplitude and phase from the corrupted OFDM frame. Note that the algorithm does not require any prior information about the disturbance. The proposed algorithm is validated through thorough simulations, covering different modulations, noise variations, and spectral leakage cases, and compared with standard OFDM performance without the algorithm. Through our experimentation, it has been demonstrated that for a disturbance frequency not equal to one of the OFDM subcarriers, the algorithm can estimate the disturbance frequency with high precision, resulting in a gain of more than 80 dB when compared to the case without the algorithm. For a disturbance frequency equal to one of the OFDM subcarriers, a simple coding technique such as Hamming & interleaving enables the user to remove the disturbance.