Order adaptive local polynomial FT based interference rejection in spread spectrum communication systems

Methods for jammer rejection in the spread spectrum communications, based on the time-frequency representations, have been proposed in order to improve the desired signal receiving performances. In this paper nonstationary jammers were considered and the local polynomial Fourier transform (LPFT) was used to represent the received corrupted signal. Time-varying filtering was implemented in optimal LPFT domain, having in mind that the LPFT is linear with respect to the signal. An order adaptive algorithm of the LPFT calculation is presented. Performance of the proposed nonparametric method is tested in the presence of linear and sinusoidal FM interferences in the noisy signal, without any a priori assumption about the jammer form. The proposed method may be successfully extended to the case of multiple jammers. Obtained results in terms of the bit error rate (BER) values show the achieved improvements. Procedure for an efficient optimization of the first-order LPFT is presented.