Eleven DSL semiconductor and system vendors announced their commitment to discrete multi-tone (DMT) modulation as the line code for standard-compliant very-high-bit-rate digital subscriber lines (VDSL). The companies noted that over 36 million ADSL lines deployed worldwide at the end of 2002 were using DMT modulation. The companies claim the technology will scale to more than 70 Mbps downstream and over 50 Mbps upstream on existing telephone lines. The backers of DMT VDSL include Alcatel, Analog Devices, Broadcom, Ericsson, Ikanos Communications, Intel, LSI Logic, Nokia, STMicroelectronics, Texas Instruments and Thomson Multimedia.
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- Companies advocating QAM-based VDSL include Infineon Technologies and Metalink. Broadcom was an early supporter of QAM VDSL, but recently switched sides and announced its support for DMT line coding.
The TiE1.4 committee is meeting later this month to consider whether DMT or QAM should be adopted as a standard. A “VDSL Olympics” is currently underway, with both sides presenting their technical arguments as to which is best.
