Standards Body Weighs in to Keep ADSL-Lite on the Ground
By Phil Jones
08-DEC-97
The future of ADSL as a consumer service standard is under scrutiny at this week's ANSI technical
committee meetings in Sacramento, California, as the experts ponder how "lite" versions of ADSL can
be supported without fragmenting current ADSL standards.
The deliberations of the ANSI T1/E1.4 committee, which is responsible in the US for defining the
Asymmetric Digital SL physical layer standards - T1.413 - are a response to growing demand from
carriers and Internet service providers for a less complex, and cheaper way of rolling-out ADSL-like
services to residential communities.
Current ADSL standards, which support downstream (to the consumer) speeds of 8 Mbps are
considered too sophisticated and expensive for consumer networks. This has encouraged some vendors
to propose new proprietary standards which are slower, but which do not need new equipment to be
installed at the customer premises, significantly cutting carrier roll-out costs.
The emergence of "lite" versions of ADSL independently of the ADSL Forum and ANSI standards
processes, is worrying some members of the ADSL community who fear existing standards may be
compromised, slowing ADSL systems market development just as the technology's long effort to be
accepted appeared to be reaching a successful conclusion.
"The problem is that in the last six to 12 months so many vendors have come forward with some
many flavors they have confused the market," said Nigel Cole, chairman of the ADSL Forum technical
committee and vp of business development with Orckit, a specialist ADSL developer.
One of the new crop of vendors with its own solution is Rockwell Semiconductor Systems, which
recently offered its CDSL (Consumer Digital Subscriber Line) to the International Telecommunication
Union as a potential ADSL-lite standard. Rockwell claims CDSL will be ready in the second half of
1998, offering downstream services of around 1 Mbit/s, and an upstream link of 128 Kbit/s. Critically,
says Rockwell., it will not require a splitter at the customer premise.
However, potential rivals point out, "They [Rockwell] don't have a product" yet, and accuse the
company of rocking the ADSL boat, just as the opportunity for market take-off demands stability.
Solutions like Rockwell's will not work with existing ADSL central office installations, forcing carriers to
consider supporting a separate service infrastructure for business users and residential users.
A preferable approach, according to the ADSL Forum's Cole, is for a lite version of ADSL to be
developed that is backward compatible with existing ADSL specifications. "The natural way to do it is
as a subset of existing ADSL standards," he said. This, he hopes, is the result that will emerge from
this week's ANSI meetings.
I am hoping that the ADSL Forum will endorse the Aware ADSL-Lite solution and publicly condemn the Rockwell CDSL solution. |
