A Blind Adaptive Receiver with Decision-Directed Steering Vector for DS-CDMA Downlink

Quee-Seng QUEK  Hiroshi SUZUKI  

Publication
IEICE TRANSACTIONS on Communications   Vol.E83-B   No.8   pp.1656-1663
Publication Date: 2000/08/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Personal, Indoor and Mobile Radio Communications)
Category: 
Keyword: 
DS-CDMA,  orthogonalizing matched filter (OMF),  RAKE,  mismatch problem,  multipath channels,  

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Summary: 
A blind technique for adaptive signal suppression in multipath DS-CDMA communication channels for the downlink is considered. Its performance is degraded when mismatch problem occurs when multipath components arrive with fractional-chip delays. In order to surmount this problem, Multiple Finger Expansion Optimal Filter (MFE-OF) was recently proposed to estimate the received desired signal subspace using fractionally delayed despreading fingers. However, MFE-OF requires much computational complexity for good performance. In this paper, a modification to the MFE-OF is introduced by utilizing decision-directed steering vector to reduce the number of fingers required by MFE-OF down to that of the conventional OMF-RAKE without much performance degradation. This modified receiver is called Decision-Directed Optimal Filter (DDOF). Computer simulation validates the effectiveness of the new receiver to increase the downlink capacity of DS-CDMA systems.