| || Performance Degradation in Pre-rake Frequency-division Duplex/ Direct Sequence-code Division Multiple Access Systems
Author : Subhas, C.;Naidu, K. Rama;Reddy, Y. Venkatarami
Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 282-289
Subject : 62 Engineering;Defence Science Journal
Keywords : Direct sequence-code division multiple access;DS-CDMA;rake receiver;pre-rake;inter-symbol interference;frequency-division duplex;FDD;channel prediction
Abstract : 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, a method for channel prediction to evaluate the pre-rake system using binary phaseshift keying (BPSK) modulation in frequency-division duplex (FDD) through analytical and computer simulations for DS-CDMA downlink has been proposed. The performance of the system was also evaluated under ideal and predicted channel conditions using different spreading codes. The findings will have widespread applications in defence communication equipment.