On Narrowband Interference Suppression in TDCS with WFRFT Preprocessing

Abstract

We propose a modified transform domain communication system (TDCS) structure with weighted fractional Fourier transform (WFRFT) preprocessing over the channel with additive white Gaussian noise (AWGN) and narrowband interference (NBI). The majority of NBI can be removed by adding zeros to TDCS’s basic function (BF) amplitude vector at these subcarriers where strong NBI exists, and the corresponding residual NBI can be further greatly eliminated in time-frequency domain through WFRFT processing. To achieve the best bit error rate (BER) performance, we defineγas the normalised cross relationship coefficient between TDCS’s BF vector and residual NBI vector and prove that the corresponding WFRFTαoptcan be obtained by minimising the magnitude ofγ. Numerical simulations are conducted to evaluate the proposed system’s performance with regard to NBI suppression.