Future of Asymmetric  DSL

As customer demand for triple-play services - voice, data, and video - increases , so does the competition between carriers/DSL service providers and cable operators.  While the later are already offering HDTV, VoD, VoIP and other high-speed services, DSL providers cannot compete with the high data rates requirements as existing xDSL technology fail to achieve them.  The need for some high speed fiber-like broadband capability is in place, and the sooner - the better.
One solution is indeed to extend fiber-to-the-home, every home.  But this has economical implications, since fiber is has quite a high cost.  Creating the infrastructure also take time, contradicting our "the sooner - the better" assumption.  The solution is preferably to be a DSL solution, using existing POTS , being economically profitable for carriers, and offer great deal of bandwidth for consumers to enjoy rich and smooth contents off the net.

VDSL2
Very-high-bit-rate Digital Subscriber Line 2 (VDSL2) has been in developement by several chip manufacturers for quite some time, and made another important step with the publication of ITU-T Recommendation G.993.2 on May 2005.

VDSL2 will take notes from the standardization process of ADSL.  Bodies such as the DSLforum evaluated and tested the performance of ADSL in several conditions, to determine the best modulation techniques, deploying schemes, and more factors which influenced and shaped the final standard of ADSL.  Therefore it is no surprise to see that VDSL2 chose DMT over CAP as was did ADSL.  It also Support a wide range of test parameters, adopted from ADSL2.
Furthermore, observing the many challenges (along with their solutions) associated with deploying ADSL on a massive scale, including the lack of detailed standardization and network management tools, spectrum management issues, specifications for filters, and more, might allow mass deployment of VDSL2 much earlier than happened with ADSL.

VDSL2 support both asymmetric and symmetric transmission, with an aggregate data rates up to 200Mbps on twisted pairs - 100Mbps for downstream and 100Mbps for upstream .  Its allocated spectrum is increased from 12khz as in the case of its predecessor the VDSL, up to 30khz.

Figure 1. Spectrum allocation in VDSL2 is increased to 30khz

Interoperability with existing products employing VDSL, ADSL, ADSL2+ is another benefit for carriers who want to invest in VDSL2, as it makes deploying of the new VDSL2 easier, and also helps migrate costumers from the old technology to the new one.  In addition, VDSL2 support configuration of both ATM and IP over standard cooper lines, unlike ADSL which is always ATM based.
Furthermore, VDSL2 is supported by g994.1, the handshake protocol for DSL equipment.

Among the many benefits of VDSL2 perhaps the most interesting feature is the support of a wide range of deployment scenarios, which is unique to VDSL2.  Transceiver and power specifications have been defined to deal with interference that are likely to occur in the types of environments most likely to house VDSL2 equipment, such as central offices, wiring cabinets in neighborhoods or office parks, or within buildings.  A scenario for longer reach has also been examined.
Other benefits include:

• Enabling complete triple-play services (video-audio-data).
• The best cover of subscribers with fiber-fast broadband services the market has to offer.
• Improved framing based on ADSL2, with improved overhead channel, and support of Impulse Noise Protection (INP).
• Improved initialization, including a channel discovery phase, for better interoperability.
• Variety of network management and testing tools.

ADSL3 ???
It is very unlikely to see any ADSL3 standardization any time soon, as there is no technology planning from the side of manufacturers, and no signs of any standard organization.  the ITU is still busy finalizing ADSL2, working out all the problems still need attention.  It seems that VDSL2 will battle it out with ADSL2 to proclaim its place in the future, and if everything goes as planned it will become the dominant technology due to its very high data rate.  Actually, there are many manufacturers willing to bet on it, and have already began developing chips for the technology.
For those do not want to give up on ADSL so quickly, there are plans for a lighter version of VDSL2, which offers 20-25Mbps of downstream (rather then 10-17 as in ADSL2+), and can be thought of as unofficial ADSL3, although standards organizations would really prefer to leave the name VDSL2.

Take a quiz

Play DSL-Hangman