A 70 Mb/s variable-rate DMT-based modem for VDSL

Very high-speed digital subscriber line (VDSL) technology can deliver data at multi-Mbits/s over the unshielded, twisted pair in overlay to the plain old telephone service (POTS) and ISDN services. Discrete multi-tone (DMT) is one candidate for the modulation of VDSL. The DMT transmit signal is the sum of independent quadrature amplitude modulated (QAM) carriers spread over a bandwidth of 11.04 MHz. Time division duplexing (TDD) is used to provide a half-duplex communication channel over a single pair. This chip integrates the complete digital signal processing required by a TDD-DMT VDSL system and the Transport Convergence (TC) sublayer functions such as (de)interleaving, Reed-Solomon (de)coding, (de)scrambling, (de)framing and the ATM-specific TC functions. It can be used both at the network termination (NT) and the line termination (LT) side.