Hardware design and performance analysis of VDSL transceivers

With a hybrid fiber/twisted-pair architecture, data rates up to about 50 Mbit/s can be transmitted over installed twisted-pair cables in the distribution part of twisted-pair access networks. Based on a channel model for twisted-pair cables for frequencies up to 40 MHz derived from measurements, different transmission formats are compared. It is concluded that frequency division multiplexed VDSL (Very high bit rate Digital Subscriber Line) systems based on QAM (Quadrature Amplitude Modulation) or CAP (Carrierless AM/PM) are a good choice. In this paper, two scalable system proposals are presented. Both systems can transmit 12.5 Mbit/s symmetrically over a distance of about 800 m. System 1 enables as well the asymmetrical transmission of 50/2 Mbit/s over 280 m, whereas system 2 enables the symmetrical transmission of 25 Mbit/s over 300 m. Based on the required filter lengths of the equalizer and the wordlengths of the signals within the adaptive filters, the hardware complexity of the proposed VDSL transceivers is determined