A new finger placement algorithm for the Generalized RAKE receiver

Generalized RAKE (G-RAKE) and linear minimum mean square error (LMMSE) are two equalization techniques designed for advanced receivers in wideband code division multiple access (WCDMA) / high-speed downlink packet access (HSDPA) systems. In this paper, we first review the theoretical properties and discuss some implementation issues of the G-RAKE technique. The equivalence between G-RAKE and LMMSE chip-level equalization (CE) was then evaluated under various system implementation constraints. Finger placement algorithm is a key factor in implementation and greatly affects the performance of G-RAKE. Optimal solution is prohibitively complex even for small number of fingers since the symbol signal to interference and noise ratio (SINR) is not a convex function of the finger delays. Here we proposed a novel and computationally efficient finger placement algorithm that significantly reduces the complexity of the optimal solution with a reasonable performance loss. Such algorithm is based on the maximum diagonal weight and therefore named maximum weight placement (MWP). The balance on the performance and the complexity of such algorithm is compared to many proposed algorithms through analysis and simulation results.