EURASIP Journal on Applied Signal Processing 
Volume 2006 (2006), Article ID 34343, 16 pages
doi:10.1155/ASP/2006/34343

A Novel Efficient Cluster-Based MLSE Equalizer for Satellite Communication Channels with M-QAM Signaling

Eleftherios Kofidis,1 Vassilis Dalakas,2 Yannis Kopsinis,3 and Sergios Theodoridis2

1Department of Statistics and Insurance Science, University of Piraeus, 80 Karaoli & Dimitriou Street, Piraeus 185 34, Greece
2Department of Informatics and Telecommunications, University of Athens, Panepistimioupolis, Ilissia 157 84, Athens, Greece
3Institute for Digital Communications, School of Engineering and Electronics, the University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh EH9 3JL, United Kingdom

Received 24 April 2005; Revised 19 December 2005; Accepted 18 February 2006

Abstract

In satellites, nonlinear amplifiers used near saturation severely distort the transmitted signal and cause difficulties in its reception. Nevertheless, the nonlinearities introduced by memoryless bandpass amplifiers preserve the symmetries of the M-ary quadrature amplitude modulation (M-QAM) constellation. In this paper, a cluster-based sequence equalizer (CBSE) that takes advantage of these symmetries is presented. The proposed equalizer exhibits enhanced performance compared to other techniques, including the conventional linear transversal equalizer, Volterra equalizers, and RBF network equalizers. Moreover, this gain in performance is obtained at a substantially lower computational cost.