On combining schemes for W-CDMA RAKE reception in the presence of interpath interference

In Tantikovit et al., (2000), we presented a signal model for interpath interference (IPI) in low spreading factor long-code wideband-CDMA (W-CDMA) systems and showed that the impact of IPI can be decomposed into branch correlation and co-channel interference similar to those in an adaptive array system. We consequently derived optimum and suboptimum combining schemes for the RAKE receiver, which provide significant improvement over the conventional maximum-ratio combining. In this paper, we derive the theoretical probability density function (pdf) of the signal-to-interference-plus-noise ratio and outage probability of the optimum combining scheme in a semi-analytical fashion. The obtained analytical results closely agree with simulation results.