On the decision-directed equalization of constant modulus signals

Papadias, Constantinos B;Slock, Dirk T M
Asilomar 1994, 28th IEEE Annual Asilomar Conference on Signals, Systems and Computers, October 31-November 2, 1994, Pacific Grove, USA

Decision-Directed (DD) equalization is the most primitive Blind Equalization (BE) method forthecancelling of Inter-Symbol-Interference (ISI) in data communication systems. Even though DD equalizers are believed to be unable to open the channel eye when it is initially closed, this does not seem to be true in the case of Constant-Modulus (CM) constellations (pure phase modulation). We investigate the shape of the DD cost function in this case and obtain several interesting results that indicate that the DD algorithm should be capable of opening a closed channel eye in the CM case. Based on this fact, we propose a novel hybrid CMA-DD equalization scheme that others an appealing alternative to the Generalized Sato (GSATO) algorithm for QAM constellations. Our theoretical claims about the performance of DDequalizers as well as the performance of our novel scheme are verified through computer simulations.

Pacific Grove
Communication systems
Eurecom Ref:
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