A Novel Efficient Cluster-Based MLSE Equalizer for Satellite Communication Channels with -QAM Signaling
- PDF / 1,724,454 Bytes
- 16 Pages / 600.03 x 792 pts Page_size
- 62 Downloads / 181 Views
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 1 Department
of Statistics and Insurance Science, University of Piraeus, 80 Karaoli & Dimitriou Street, 185 34 Piraeus, Greece of Informatics and Telecommunications, University of Athens, Panepistimioupolis, Ilissia, 157 84 Athens, Greece 3 Institute for Digital Communications, School of Engineering and Electronics, the University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh EH9 3JL, UK 2 Department
Received 24 April 2005; Revised 19 December 2005; Accepted 18 February 2006 Recommended for Publication by Bernard Mulgrew 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. Copyright © 2006 Hindawi Publishing Corporation. All rights reserved.
1.
INTRODUCTION
The role of a satellite is to receive a signal from an earth station or another satellite (uplink) and, acting as a simple repeater, to transmit it to another earth station or satellite (downlink) [1]. The need to maximally exploit on-board resources in a satellite communication system often imposes driving a high power amplifier (HPA), such as the traveling wave tube amplifier (TWTA), at or near its saturation point, resulting in a nonlinear distortion of the signal, and rendering the overall link nonlinear. To overcome nonlinear distortions, constant modulus constellation symbols (e.g., 4QAM) are commonly used [2]. However, large QAM signal constellations have to be adopted whenever high bandwidth efficiency is required [3], resulting in severe nonlinear distortions. Two approaches have been proposed for solving the problem of correct reception of the transmitted signal in those cases: (a) equalization [4, 5] and (b) predistortion or power amplifier linearization [6–8]. Equalization refers to processing the signal at the receiver side in order to recover the transmitted data, thus postcanceling the link’s nonlinear (amplifier) and linear (multipath) distortions. Conventional linear equalizers combat only the intersymbol interference (ISI), introduced by the propagation channel, while nonlinear equalizers aim also at equalizing the nonlinear effects of the HPA. The main
drawback of the equalization approach is the additional cost and the computational load it entails for each terminal. On the other hand, predistortion techniques ai
Data Loading...
