INTERFERENCE MITIGATION IN SPREAD-SPECTRUM SYSTEMS BY WAVELET COEFFICIENTS THRESHOLDING

This paper studies a potential EMI (ElectroMagnetic Interference) reje ction technique for the GPS Standard Positioning Service in an avionic s environment. Its generalisation to any Direct Sequence Spread Spectr um (DSSS) Systems is also considered. The paper gives a brief overview of Wavelet Theory, which is well established for noise reduction but which is applied here to Continuous Wave Interference (CWI) and narrow band interference. The originality of this work lies in a method for s ignal rejection, taking into account features in both time and frequen cy domains to account for the non-stationary characteristics of the in terference. Because the software-based receiver is more flexible, less expensive and more accurate compared with typical hardware receivers, a Generic GPS Receiver has been implemented in software [1] to valida te the anti-jamming technique developed in this paper. The aim of the MonteCarlo simulations is to get a good idea of the Performances of th e Wavelet Filter against a various types of Interferences and to compa re the results with traditional processing.