Linear-conjugate/linear filtering for interference rejection in multi-rate DS/CDMA systems

In this work we introduce a new multiuser detector for interference suppression in DS/CDMA systems, based on the minimization of a modified MMSE-like cost function, and which may possibly entail an independent processing of the data and of their complex conjugate. The proposed detection structure is then specialized to the relevant case that the interference consists of a secondary CDMA network whose bit-rate is slower than that of the primary network: interestingly, interference suppression entails a periodically time-varying (PTV) detection rule. We also address the issue of adaptive detection, and present a new RLS algorithm suited for the tracking of the PTV solution. As to the performance assessment, we give a closed-form formula for the system error probability, while numerical results show that the new detection structure, and its adaptive version, outperform previously known receivers