Time-varying narrow-band interference rejection in asynchronous multiuser DS/CDMA systems over frequency-selective fading channels

In this paper, me handle the problem of joint suppression of multiple-acces s interference (MAI) and narrowband interference (NBI) in fading, dispersiv e channels. The detectors me consider are linear, one-shot structures, whic h allow for possible window enlargement and signal-space oversampling to im prove performance. We focus on both zero-forcing and minimum-mean square-er ror design strategies, showing that the presence of NBI generally requires a time-varying processing of the observables, no matter what the optimizati on criterion. A thorough performance assessment of the proposed detectors i s also presented, either through analytical formulas or through computer si mulations. We finally deal with the problem of blind suppression of both MA I and NBI, introducing batch-estimation procedures to be implemented offlin e, which require very little and sometimes no prior knowledge as to the int erference structure.