New nonlinear algorithms for narrow-band interference suppression in CDMA spread-spectrum systems

The narrow-band interference suppression capability of spread-spectrum syst ems can be further enhanced by employing interference suppression filters: This paper proposes a number of new nonlinear algorithms;for narrow-band in terference suppression in code division multiple access spread-spectrum sys tems. Our research consists of two parts. 1) We propose a multiuser decisio n-directed Kalman (MDK) filter, which has the same performance as the nonli near approximate conditional mean (ACM filter but a much simpler algorithm 2) We use the nonlinear function in the ACM and the MDK filters to develop nonlinear adaptive least mean square filters with significantly improved pe rformance. Simulation results indicate that our nonlinear algorithms outper form conventional linear ones.