The European Telecommunications Standards Institute's (ETSI's) TM6 sub committee has decided to support both Quadrature Amplitude Modulation (QAM) and Discrete Multi-Tone (DMT) line coding in its VDSL standard. The decision to support dual line coding enables European service providers to choose for themselves which form of modulation they want for their VDSL network deployments. Infineon Technologies, which offers a QAM-based VDSL chip, said "the best way to accelerate VDSL deployment is to encourage true competition, in which component choice is based on price, performance, silicon size, and vendor reputation." Infineon claims to have shipped over 4 million QAM-VDSL ports, representing more than 2.5 million active lines.
The contribution in support of dual line code for VDSL can be found at the following URL:
ftp://ftp.t1.org/T1E1/E1.4/DIR2003/3E141761.pdf
http://www.etsi.orghttp://www.infineon.com
- Last month, 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 followed the release of data from the "VDSL Olympics," a series of performance tests conducted by Telcordia Technologies and BT.
Separately, the IEEE's 802.3ah Ethernet in the First Mile (EFM) Task Force selected DMT as its worldwide line-coding standard for VDSL.
