Spectrally Compatible Iterative Water Filling
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Spectrally Compatible Iterative Water Filling Jan Verlinden,1 Etienne Van den Bogaert,2 Tom Bostoen,1 Francesca Zanier,3 Marco Luise,4 Raphael Cendrillon,5 and Marc Moonen6 1 Access
Networks Division, Alcatel, Francis Wellesplein 1, Antwerpen 2018, Belgium & Innovation Department, Alcatel, Francis Wellesplein 1, Antwerpen 2018, Belgium 3 Department of Telecommunication Engineering, University of Pisa, 56122 Pisa, Italy 4 Department of Information Engineering, University of Pisa, 56122 Pisa, Italy 5 School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, QLD 4072, Australia 6 Department of Electrical Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, Leuven-Heverlee 3001, Belgium 2 Research
Received 2 December 2004; Revised 1 July 2005; Accepted 12 July 2005 Until now static spectrum management has ensured that DSL lines in the same cable are spectrally compatible under worstcase crosstalk conditions. Recently dynamic spectrum management (DSM) has been proposed aiming at an increased capacity utilization by adaptation of the transmit spectra of DSL lines to the actual crosstalk interference. In this paper, a new DSM method for downstream ADSL is derived from the well-known iterative water-filling (IWF) algorithm. The amount of boosting of this new DSM method is limited, such that it is spectrally compatible with ADSL. Hence it is referred to as spectrally compatible iterative water filling (SC-IWF). This paper focuses on the performance gains of SC-IWF. This method is an autonomous DSM method (DSM level 1) and it will be investigated together with two other DSM level-1 algorithms, under various noise conditions, namely, iterative water-filling algorithm, and flat power back-off (flat PBO). Copyright © 2006 Hindawi Publishing Corporation. All rights reserved.
1.
INTRODUCTION
More and more users today have broadband access to the Internet based on ADSL (asymmetric digital subscriber line) technology. However, still not all users can have this service, because they are located too far from the central office. People who have broadband access today prefer to have even higher data rates. DSM is a technique that tries to optimize the rates and reach for all users in a network. As such a telecom operator can offer broadband access to as many customers as possible and provide them with the optimal data rates. Rate and reach for a certain DSL service are limited by crosstalk. Crosstalk is noise that comes from other DSL lines in the same binder. Due to electromagnetic coupling, the signal of one line indeed interferes with the signal of the other line. DSM tries to optimize the spectrum that is used for a certain line, such that it does not allocate a higher power spectral density (PSD) than necessary to achieve the requested bit rate. For DSM, several algorithms exist. In this paper we will focus on DSM level 1, that is, autonomous algorithms that do not need coordination from a central agent. We will develop a new DSM method for downstream ADSL, referred to
as spe
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