Open AccessVariable step-size LMS adaptive filters for CDMA multiuser detection
Author(s) -
Карен Егиазарян,
Pauli Kuosmanen,
Ciprian Radu Bilcu
Publication year - 2004
Publication title -
facta universitatis. series electronics and energetics/facta universitatis. series: electronics and energetics
Language(s) - English
Resource type - Journals
eISSN - 2217-5997
pISSN - 0353-3670
DOI - 10.2298/fuee0401021e
Subject(s) - code division multiple access , convergence (economics) , least mean squares filter , algorithm , multiuser detection , variable (mathematics) , computer science , adaptive filter , transmission (telecommunications) , covariance matrix , rate of convergence , mathematics , control theory (sociology) , telecommunications , channel (broadcasting) , control (management) , artificial intelligence , mathematical analysis , economics , economic growth
Due to its simplicity the adaptive Least Mean Square (LMS) algorithm is widely used in Code-Division Multiple access (CDMA) detectors. However its convergence speed is highly dependent on the eigen value spread of the input covariance matrix. For highly correlated inputs the LMS algorithm has a slow convergence which require long training sequences and therefore low transmission speeds. Another drawback of the LMS is the trade-off between convergence speed and steady-state error since both are controlled by the same parameter, the step-size. In order to eliminate these drawbacks, the class of Variable Step-Size LMS (VSSLMS) algorithms was introduced. In this paper, we study the behavior of some algorithms belonging to the class of VSSLMS for training based multiuser detection in a CDMA system. We show that the proposed Complementary Pair Variable Step-Size LMS algorithms highly increase the speed of convergence while reducing the trade-off between the convergence speed and the output error.