Detection and countermeasure of interference in slow FH/MFSK systems over fading channels

In this paper, we present an algorithm to detect unknown interference in slow frequency-hopped MM-ary frequency-shift-keying (SFH/MFSK) systems over fading channels. Both partial-band noise interference (PBNI) and multitone interference (MTI) are considered. The proposed algorithm performs the detection process after dehopping by making use of square-law detectors. We first analyze the statistical property of the outputs of the square-law detectors over one hop duration, and an appropriate threshold level is derived for detecting the interference based on a binary hypothesis testing. We also formulate the closed-form expressions for the probabilities of detection of both types of interference experienced in any particular frequency hop. The analytical results are validated by the simulation results and they reveal that the proposed algorithm is able to provide good detection performance for both types of interference and outperforms the conventional ratio–threshold test (RTT) method.