RLS Channel Estimation with Adaptive Forgetting Factor for DS-CDMA Frequency-Domain Equalization

Hiromichi TOMEBA
Kazuaki TAKEDA
Fumiyuki ADACHI

IEICE TRANSACTIONS on Communications   Vol.E92-B    No.5    pp.1457-1465
Publication Date: 2009/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.1457
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Radio Access Techniques for 3G Evolution)
DS-CDMA,  frequency-domain equalization,  channel estimation,  RLS algorithm,  

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Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can increase the downlink bit error rate (BER) performance of DS-CDMA beyond that possible with conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. Recently, we proposed a pilot-assisted channel estimation (CE) based on the MMSE criterion. Using MMSE-CE, the channel estimation accuracy is almost insensitive to the pilot chip sequence, and a good BER performance is achieved. In this paper, we propose a channel estimation scheme using one-tap recursive least square (RLS) algorithm, where the forgetting factor is adapted to the changing channel condition by the least mean square (LMS) algorithm, for DS-CDMA with FDE. We evaluate the BER performance using RLS-CE with adaptive forgetting factor in a frequency-selective fast Rayleigh fading channel by computer simulation.