Narotham, I am getting interested in PAIR. It is starting to look good. The next big technology might not be ADSL but HDSL2. It will lead well into fiber and VDSL.There is a great article about HDSL2 in
internettelephony.com
Here is a blurb from that article,cannot copy URL as it is frame based.
To support the work of writing specifications for HDSL2, the group
appointed several editors for the project. Mike Rude, senior project
engineer with ADC Telecommunications, was appointed as the lead editor
of the document. The committee also named co-editors from Level One,
Adtran, PairGain and Brooktree.
Developers continue to engage in active discussions to help resolve the
choices before the committee. The group must choose between the CAP and
PAM line codes as well as the multi-stage and sequential FEC schemes. In
addition, they must agree on a realistic noise model for mixed service
crosstalk. These issues will be addressed at an interim T1E1.4 meeting
to be held in July.
The HDSL2 objective is a standard with robust performance and benign
spectral compatibility. These are the very same characteristics that
have helped make HDSL so successful today. Developers are dedicated to
ensuring that the HDSL2 standard shares these characteristics, and they
will agree on a line code and FEC after rigorous analysis.
Market Needs
There is a strong focus on ensuring that HDSL2 system solutions are
application-driven and meet the market's cost targets and plant
management requirements. Service providers have made it clear that they
do not want to pay more for HDSL2 solutions than they do for standard
HDSL.
Manufacturers cooperating within the T1E1.4 committee understand the
importance of adopting a standards-based, rather than proprietary,
approach to HDSL2. Carriers gain two important benefits from systems
that conform to industry accepted standards:
Forward compatibility needed to integrate emerging new technologies
into existing systems
Greater flexibility in product selection decisions because they are not
tied to a single vendor.
Vendors also benefit from standards in that they can invest resources in
value-added options rather than in the development of a proprietary
interface, which may not be compatible with dependent systems from other
vendors.
Once an HDSL2 transmission and coding scheme is decided upon by the
committee and the definition and writing are complete, the standard will
undergo extensive testing. Developers anticipate that first-generation
HDSL2 chip sets will be available for trials in early to mid-1998.
One pair of copper,two T-1 lines,symmetrical,and with a better link to the future technologies.
Hiram |
