DMT Line Coding Specified for VDSL Standard in North America

The T1E1.4 committee, which is part of The Alliance for Telecommunications Industry Solutions (ATIS), decided to specify only Discrete Multi-Tone (DMT) line coding in its American National Standard (ANS) for VDSL. The DMT modulation method will be specified in the American National Standard, and the Quadrature Amplitude Modulation (QAM) method will be specified in a Committee T1 Technical Requirement (TRQ).


The decision follows the release of data from the "VDSL Olympics," a series of performance tests conducted by Telcordia Technologies and BT to help evaluate DMT and QAM's compatibility with VDSL. Among the findings: VDSL-DMT achieved the highest "payload" performance, the longest reach, and outperformed in burst noise conditions.


Richard Sekar, Vice President of Marketing for Ikanos Communications, a supplier of DMT-based VDSL silicon solutions, said the results of the VDSL Olympics and the T1 Committee decision provide the conclusive determination the industry has been waiting for on this issue. Ikanos expects that the certainty of a single VDSL line coding standard will give carriers the confidence to move ahead with plans to upgrade current DSL networks for customers wanting higher speed VDSL connections. On this front, Sekar noted that Millinet, a supplier of VDSL equipment in Korea, has recently decided to switch to the Ikanos DMT VDSL chipset instead of using a competitors' QAM solution.


Mark Tyndall, VP of Business Development for Infineon Technologies, a supplier of QAM-based VDSL silicon, acknowledged the T1 Committee decision as setting a standard for North America, but suggested that the standards question might still be open for carriers in Asia-Pacific and Europe. Tyndall said the rapid adoption of QAM-based VDSL in South Korea of the past year indicates that the technology is market ready. Infineon is hoping the ITU will specify dual line code options for its VDSL standards, allowing each carrier to choose for itself which modulation scheme is best. Infineon will also continue to push for QAM as a solution for Ethernet in the First Mile (EFM) solutions. Tyndall further noted that the VDSL Olympics testing compared existing VDSL silicon implementations rather than comparing actual line codes. Earlier this month, Infineon announced a new VDLS Modem-on-Chip (MoC) solution that it claims delivers aggregate data rate of more than 100 Mbps, including asymmetric data-rates of 70/40 Mbps and symmetric data-rates of 50/50 Mbps over single-pair copper wires. This was not the chipset that Infineon submitted for the VDSL Olympics. Sampling of the new silicon is expected in August.
http://www.atis.org/atis/PRESS/pressreleases2003/062003.htm