Frequency-Domain ICI Cancellation with MMSE Equalization for DS-CDMA Downlink

Kazuaki TAKEDA
Koichi ISHIHARA
Fumiyuki ADACHI

Publication
IEICE TRANSACTIONS on Communications   Vol.E89-B    No.12    pp.3335-3343
Publication Date: 2006/12/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e89-b.12.3335
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
Keyword: 
DS-CDMA,  frequency-domain equalization,  MMSE,  ICI cancellation,  

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Summary: 
Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can replace the conventional rake combining while offering significantly improved bit error rate (BER) performance for the downlink DS-CDMA in a frequency-selective fading channel. However, the presence of residual inter-chip-inference (ICI) after FDE produces orthogonality distortion among the spreading codes and the BER performance degrades as the level of multiplexing increases. In this paper, we propose a joint MMSE frequency-domain equalization (FDE) and ICI cancellation to improve the BER performance of the DS-CDMA downlink. In the proposed scheme, the residual ICI replica in the frequency-domain is generated and subtracted from each frequency component of the received signal after MMSE-FDE. The MMSE weight at each iteration is derived taking into account the residual ICI. The effect of the proposed ICI cancellation scheme is confirmed by computer simulation.