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Blind Adaptive Equalizer Based on CMA and LMS Algorithm
James OKELLO Kenji UEDA Hiroshi OCHI
Publication
IEICE TRANSACTIONS on Communications
Vol.E87B
No.4
pp.10121015 Publication Date: 2004/04/01 Online ISSN:
DOI: Print ISSN: 09168516 Type of Manuscript: LETTER Category: Fundamental Theories Keyword: equalizer, blind algorithm, CMA, LMS,
Full Text: PDF(325.4KB)>>
Summary:
In this letter we verify that a blind adaptive algorithm operating at a low intermediate frequency (LowIF) can be applied to a system where carrier phase synchronization has not been achieved. We consider a quadrature amplitude shift keyed (QPSK) signal as the transmitted signal, and assume that the orthogonal low intermediate sinusoidal frequency used to generate the transmitted signal is well known. The proposed algorithm combines two algorithms: Namely, the least mean square (LMS) algorithm which has a cost function with unique minimum, and the constant modulus algorithm (CMA), which was first proposed by Godard. By doing this and operating the equalizer at a rate greater than the symbol rate, we take advantage of the variable amplitude of the subcarriers and the fast convergence of LMS algorithm, so as to achieve a faster convergence speed. When the computer simulation results of the proposed algorithm are compared with the constant modulus algorithm (CMA) and the modified CMA (MCMA), we observed that the proposed algorithm exhibited a faster convergence speed.

