Global convergence of fractionally spaced Godard (CMA) adaptiveequalizers
Ye Li; Zhi Ding
Signal Processing, IEEE Transactions on
Volume 44, Issue 4, Apr 1996 Page(s):818 - 826
Digital Object Identifier 10.1109/78.492535
Summary:The Godard (1980) or constant modulus algorithm (CMA) equalizer is
perhaps the best known and the most popular scheme for blind adaptive
channel equalization. Most published works on blind equalization
convergence analysis are confined to T-spaced equalizers with
real-valued inputs. The common belief is that analysis of fractionally
spaced equalizers (FSEss) with complex inputs is a straightforward
extension with similar results. This belief is, in fact, untrue. We
present a convergence analysis of Godard/CMA FSEs that proves the
important advantages provided by the FSE structure. We show that an FSE
allows the exploitation of the channel diversity that supports two
important conclusions of great practical significance: (1) a
finite-length channel satisfying a length-and-zero condition allows
Godard/CMA FSE to be globally convergent, and (2) the linear FSE filter
length need not be longer than the channel delay spread. Computer
simulation demonstrates the performance improvement provided by the
adaptive Godard FSE
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