Code-aided adaptive narrowband interference suppression for direct-sequence spread-spectrum communications

A new and powerful method for suppressing narrow-band interference in direct-sequence spread-spectrum (DS/SS) communications systems is developed. This technique is based on the linear minimum-mean-square-error (MMSE) algorithm for multiuser detection. The NBI signal is often modeled either as a sinusoidal signal (tone) or an autoregressive (AR) signal. The NBI signal can also be a digital signal, such as would arise, for example, in a multirate signaling system. The performance of the proposed method against each of these three types of NBI is analyzed. The performance of the proposed method against NBI is then compared with the performance of some performance linear and nonlinear NBI suppression methods, and it is seen that this new method outperforms all these previous techniques of NBI suppression. The proposed NBI suppression technique can be implemented in a blind adaptive mode. A recursive-least-squares (RLS) version of this algorithm is developed. The convergence dynamics and the steady state performance of the adaptive algorithm are also analyzed.