DSL : crosstalk estimation techniques, and impact on DSM
(2010)
Files
theseAK.pdf
Open Access - Adobe PDF
- 1.52 MB
Details
- Authors
- Supervisors
- Abstract
- (en) DSL systems "Digitial Subscriber Line", take advantage of the long time not used high frequency bands of twisted pairs in order to transmit signals that may go up to 30 MHz. This band is much higher than the traditional voice band of 4 kHz. Going up in frequency allows DSL systems to transmit at a very high Bit-Rates (24 Mbps in ADSL2+, 100 Mbps for VDSL) , however it also poses various challenges. One of the challenges that may occur , is the increase of the interference between different lines, called crosstalk, at higher frequencies. Another drawback of using higher frequencies, is the fact that the direct channels of the twisted pairs are attenuated severly for long lines at higher frequencies. The attenuation of the direct channel gain for longer lines, coupled with crosstalk caused by other shorter lines in proximity would create a Near-Far problem in DSL systems when short and long lines are mixed together. Dynamic Spectrum Management or DSM was proposed to mitigate the effect of crosstalk on DSL systems. DSM exploits the information about the direct line channels, the crosstalk channels, and the ambient noise to improve the total system capacity. We may distinguish two DSM concepts: PSD coordination and Signal coordination. Both concepts necessitate the knowledge of crosstalk channels information, something that is not available under the current DSL systems. In this thesis we consider the application of DSM algorithms under practical and realistic conditions. In the first part we propose the Balanced Capacity concept as a possible solution for the Near-Far problem, then we proceed with the enhancement of several state of the art algorithms regarding DSM implementation. In the second part, we propose several practical estimation techniques for the crosstalk channel estimation. We start by estimating the crosstalk channel gain, which is sufficient for the application of PSD coordination algorithms, and then we proceed by the estimation of the total crosstalk channel which is required for the implementation of a full signal coordination. All of these estimation techniques are based on a passive or on a limited active observation of the DSL lines. Thus these estimators are practical, and can be used with the current DSL systems with minor modifications on the standards or on the users' modems.
- Affiliations
UCLouvain SST/ICTM - Institute for Information and Communication. Technologies, Electronics and Applied Mathematics
Citations
Kalakech, A. (2010). DSL : crosstalk estimation techniques, and impact on DSM. https://hdl.handle.net/2078.5/131101