A maximum likelihood digital receiver using coordinate ascent andthe discrete wavelet transform
Sharfer, I.; Hero, A.O., III
Signal Processing, IEEE Transactions on
Volume 47, Issue 3, Mar 1999 Page(s):813 - 825
Digital Object Identifier 10.1109/78.747786
Summary:In this paper, a maximum likelihood (ML) method is presented for
joint estimation of amplitude, phase, time delay, and data symbols in a
single-user direct-sequence spread-spectrum communication system. Since
maximization of the likelihood function is analytically intractable, a
novel coordinate ascent algorithm is used to obtain sequential updates
of the data symbols and all unknown nuisance parameters. The novelty of
the algorithm is due to the use of a multiresolution expansion of the
received signal and the use of polynomial rooting in the complex plane
in place of a line search over the signal delay parameter. The
multiresolution structure of the algorithm is exploited to reduce
sensitivity to impulsive noise via wavelet thresholding. Computer
simulations of the single-user system show that the algorithm has fast
convergence, and comparison with theoretical lower bounds establishes
that the algorithm achieves nearly optimal error performance
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