Adaptive nonlinear filters for narrowband interference suppression in DS-CDMA systems
Kechu Yi · Journal of Circuits and Systems · 2008
Substantial performance gains can be achieved through the use of active narrowband interference(NBI) suppression prior to despreading and demodulating.This paper proposes a non-linear adaptive filtering method based on analyzing the performance of the conventional adaptive methods in the cases of that the NBI can be modeled as a single tone,an autoregressive(AR) stochastic process or narrow band BPSK digital modulation signals.Before the adaptive filter is employed to remove NBI,we evaluate the spread spectrum signal by maximum post-probability and subtracting from the received signal,which can make back-ground noise become into Gaussian from a non-Gaussian process,so that it can eliminate the impact of the spread spectrum signal on the NBI estimation.Here the adaptive algorithm can be either NLMS or RLS.Theoretical analysis and simulation results show that the modified method behaves much better than the conventional adaptive methods.