Differential fuzzy filtering for adaptive line enhancement in spread spectrum communications

This paper presents an estimator/subtractor narrow band interference (NBI) canceller based on fuzzy logic and applied to DS-CDMA systems. The designed fuzzy canceller introduces the slow varying nature of the NBI in its rule base. In this way, we obtain an interference suppressor with the following features: (i) fusion of different NBI models in its rule base; (ii) fast adaptation capability; (iii) low computational burden, and parallel structure; (iv) linguistic mapping between its input and output variables; and (v) non-parametric conditional mean interference estimation. Two criteria have been derived to obtain the “working region” of the fuzzy canceller, which has been adapted using a reduced cost recursive least squares (RLS) algorithm. Simulation results show that the fuzzy filter is able to cope with whatever shape of interference in its working region successfully.