Performance evaluation of Pre-Rake diversity under channel prediction errors for FDD/DS-CDMA systems

The transmitter-based Pre-Rake diversity combining technique reduces the complexity, size and cost of the mobile unit (MU), while achieving the same inter symbol interference (ISI) mitigation effects of Rake receiver for direct sequence code division multiple access (DS-CDMA) systems. The technique is based on preprocessing of transmitted signal relying on knowledge of the channel state information (CSI) before transmission. In most of the previous works, this a priori information is either assumed or estimated for the uplink and the same is applied to the downlink in Time Division Duplex (TDD) systems due to channel reciprocity. In this paper, we propose a method for channel prediction to evaluate the Pre-Rake system using binary phase-shift keying (BPSK) modulation in frequency-division duplex (FDD) through analytical and computer simulations for DS-CDMA downlink. We will also evaluate the system performance under ideal and predicted channel conditions using gold codes apart from random and orthogonal spreading sequences.