Open Access

Employing LSF at Transmitter Eases MMSE Adaptation at Receiver in Asynchronous CDMA Systems

EURASIP Journal on Wireless Communications and Networking20092008:298784

DOI: 10.1155/2008/298784

Received: 22 July 2008

Accepted: 11 December 2008

Published: 18 January 2009

Abstract

The Lebesgue spectrum filter (LSF), a finite impulse response (FIR) filter whose coefficients decay exponentially with a negative factor , is shown to be effective preprocessing for spreading code in asynchronous code-division multiple-access (CDMA) systems. The LSF has only been studied independently from the well-known minimum mean-square error (MMSE) filter, an optimal FIR filter in the mean-square error sense. In this paper, we propose an efficient structure, employing the LSF at the transmitter and the MMSE filter at the receiver, for asynchronous CDMA systems. We employ a spreading code preprocessed by the LSF (referred to as LSF-code), and the LSF-code supplies a "best" initial estimate (among the ones obtained without any a priori information) to an adaptive algorithm for the MMSE filter, leading to significant reduction of iterations in adaptation. This is verified by computer simulations. Also we investigate the link between the LSF and the MMSE filter by examining their autocorrelation properties.

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Authors’ Affiliations

(1)
Amari Research Unit (BSI)
(2)
Next Generation Mobile Communications Laboratory (CIPS)

Copyright

© Masahiro Yukawa et al. 2008

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.