At present, five standards
organizations/forums have begun work on VDSL:
- T1E1.4--The U.S. ANSI
standards group T1E1.4 has just begun a project for VDSL, making
a first attack on system requirements that will evolve into a
system and protocol definition.
- ETSI (European
Telecommunication Standards Institute)--The ETSI has a VDSL
standards project, under the title High-Speed Metallic Access
Systems, and has compiled a list of objectives, problems, and
requirements. Among its preliminary findings are the need for an
active NT and payloads in multiples of SDH virtual container
VC-12, or 2.3 Mbps. ETSI works very closely with T1E1.4 and the
ADSL Forum, with significant overlapping attendees.
- DAVIC--DAVIC has taken the
earliest position on VDSL. Its first specification due to be
finalized will define a line code for downstream data, another
for upstream data, and a MAC for upstream multiplexing based on
TDMA over shared wiring. DAVIC is specifying VDSL only for a
single downstream rate of 51.84 Mbps and a single upstream rate
of 1.6 Mbps over 300m or less of copper. The proposal assumes,
and is driven to a large extent by, a passive NT, and further
assumes premises distribution from the NT over new coaxial cable
or new copper wiring.
- The ATM Forum--The ATM
Forum has defined a 51.84-Mbps interface for private-network
User-Network Interfaces (UNIs) and a corresponding transmission
technology. It has also addressed the question of CPE
distribution and delivery of ATM all the way to premises over
the various access technologies described above.
- The ADSL Forum--The ADSL
Forum has just begun consideration of VDSL. In keeping with its
charter, the Forum will address network, protocol, and
architectural aspects of VDSL for all prospective applications,
leaving line code and transceiver protocols to T1E1.4 and ETSI
and higher-layer protocols to organizations such as the ATM
Forum and DAVIC.
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