A nonlinear narrowband interference suppression technique for spread-spectrum CDMA communications

In this paper, a new nonlinear approach for narrowband interference (NBI) suppression in code-division multiple-access (CDMA) systems is proposed. The developed scheme is an adaptive nonlinear predictor that consists of an (N+1)-level quantizer, an adaptive linear filter, and three adders, where N is the number of users in the CDMA system. It could be regarded as an enhancement to the nonlinear offset predictor presented by (Wang et al., 1997) with a more appropriate offset compensation scheme being derived and employed here. Computer simulation results support that this modified offset predictor performs much better than the original one with only a slight increase in complexity. As compared to the nearly optimal approximate conditional mean filter, it achieves almost the same performance even at very low signal-to-noise ratio, but involves much less complexity.