Abstract

Digital subscriber line (DSL) is considered as an attractive approach to transmit high-speed data due to its advantage in the provision of affordable broadband services in a wide range of end users without massive capital outlays. Very-high-speed DSL (VDSL) is the latest generation of the xDSL family. It is a promising internet access technique for broadband services, which is capable of supporting high-definition television (HDTV), Voice over IP, and general Internet access over a single twisted pair of wires. In order to overcome the harsh VDSL transmission environment and to realize a reliable high-speed data transmission, equalization technique is required at the receiver to compensate for the channel attenuation and distortion. In this thesis, we focus on the design and performance study of VDSL systems using the per-tone equalization (PTEQ). Some background material pertaining to VDSL systems and equalization techniques is first presented. The per-tone equalization technique is then investigated. Based on a two-port model of the subscriber loop, namely, the so-called ABCD theory, the transfer function of various VDSL test loops are well formulated and simulated. A practical VDSL system with configurations following the standard as well as the PTEQ in the receiver is designed and simulated. Performance study is conducted over several VDSL test loops with various channel conditions, showing a great improvement on the SNR of the received signal and the overall transmission bit-rate of the VDSL system as a result of employing the PTEQ. In order to reduce the computational complexity of the training-based PTEQ initialization, a few adaptive schemes based on the NLMS and SR-RLS algorithms are proposed. Various simulation results regarding the convergence speed of the two adaptive algorithms, the number of equalizer taps and different VDSL test loops are presented. A comparison of the performances of the two adaptive initialization schemes is also presented