To all,this answers the questions about ADSL and VDSL from this weeks internet telephony articles.
internettelephony.com
Worth more with a V
VDSL spells even higher bandwidth over copper wire--as long as there's
fiber in the loop
MICHAEL SHARIFF
As telephone companies rush to begin delivering asymmetrical digital
subscriber line services, the next generation of equipment aimed at
boosting the bandwidth of existing copper plant promises to deliver 10
times the speed. Joining the digital subscriber line lexicon is very
high speed digital subscriber line technology.
VDSL operates at rates of up to 51.84 Mb/s, compared with the typical
maximum ADSL speed of 6.3 Mb/s (Figure 1). It can be deployed to homes
that are connected via copper to optical network units (ONUs) that, in
turn, are connected to central offices or host digital terminals via
fiber. At a cost of about $1000 per line, VDSL will be economically
competitive with hybrid fiber/coax (HFC) architectures for delivering
broadband services to residential customers.
Initial applications for VDSL are asymmetrical, including
video-on-demand with simulated VCR controls, home shopping and Internet
access, all of which require more downstream than upstream capability to
the end user. Early implementations call for upstream rates of 1.6 Mb/s
to 2.3 Mb/s, although the development of fully symmetrical services is
still possible.
VDSL offers telephone companies an alternative to switched digital video
and cable technologies. Telcos can begin to deploy ADSL, while launching
their long-awaited fiber-to-the-curb (FTTC) platforms. VDSL also
satisfies concerns commonly associated with ADSL about providing
sufficient live video capacity and quality to compete effectively with
HFC networks. Its downstream bandwidth will clearly eliminate any
shortfall on that front.
Here is another blurb from that same issue.
In the late 1980s and early 1990s, the obvious remedy for supplying
greater bandwidth was to bring fiber into the local loop as a first step
toward extending it to the home. LECs clearly saw fiber's bandwidth
advantage over copper and valued the fact that that fiber's higher
bandwidth could be distributed more easily in the loop.
Moreover, fiber positioned LECs for future growth. Today, however, while
planners still envision fiber in the loop (FITL) as the right long-term
choice, the realities of the 1990s--unexpected access growth,
competition and corporate downsizing--have intensified the search for
simpler and faster methods of speeding up the final link to subscribers.
Against this backdrop, planners are considering "virtual copper pairs"
or the use of electronics to extend the life of their embedded outside
plant infrastructure. Similar to FITL technology, the underpinning
digital signal processing (DSP) technology allows bandwidth to easily be
distributed throughout the copper loop. As an interim solution, it
enables planners to take advantage of today's copper plant and prepare
for future migration to a fiber-fed local loop.
And last but not least,here is a short story about HLIT.
S-A, HARMONIC TOUT THEIR WARES
As cable engineers pack their bags for Orlando next week in anticipation
of the Cable-Tec Expo, vendors are starting to unpack their new product
lines, with Scientific-Atlanta and Harmonic Lightwaves leading the way.
Scientific-Atlanta is using the show as an official marking point of its
entry into the Sonet market, starting with its Sonet multiplexer, the
Prisma Digital Transport.
Harmonic Lightwaves is using the show to plant its flag firmly in the
network management arena. Its new MEM 5000 multiple element management
system is the first system designed to manage any element manager, as
long as it is simple network management protocol-based, said Guy
Sucharczuk, product manager at Harmonic Lightwaves.
Tim |
