Multitone interference detection after dehopping process in slow FH/BFSK systems over Rayleigh fading channels

This paper presents an algorithm to detect unknown multitone interference (MTI) which is commonly encountered in slow frequency-hopped spread spectrum (FH-SS) systems over a Rayleigh fading channel. The least-squares (LS) autoregressive (AR) spectral estimation method is used in our algorithm. The proposed algorithm performs the detection process after dehopping, hence, it can be used to provide the side information whether the MTI is present or absent for optimum maximum-likelihood (ML) FH-SS receivers. The fast Fourier transform (FFT) can also be used to implement this detection algorithm. Computer simulations are conducted to evaluate detection performance of both algorithms and comparisons are presented. Numerical results show that the MTI can be detected by both algorithms even at very low interference power (10 dB lower than signal power). Performance comparisons reveal that the proposed algorithm using the AR method is able to locate the MTI within the desired FH band more precisely than the FFT-based algorithm.