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Telecom operators around the world are including existing twisted-pair loops in their next-gen broadband access networks. Very-High-Data-Rate Digital Subscriber Line (VDSL) has the capability to transmit high-speed data over short reaches on twisted-pair copper telephone lines. The DSL market is beginning a shift from predominately ADSL deployments, to increasing numbers of VDSL deployments, mostly in the Asia-Pacific region. There is also a movement towards having so-called universal ports, which combine ADSL and VDSL functionality on the same chipset.

Demand for streaming video and video-on-demand services over broadband are expected to give an impetus to VDSL connections, especially in areas where operators are planning extensive fiber-to-the-premises (FTTP) rollouts. According to market research groups, VDSL usage will increase globally in 2005, reaching nearly seven million broadband subscribers by the year end, a 90 percent increase over 2004.

Growing demand for video, voice, and data services via broadband is providing a key opportunity for VDSL to penetrate broadband homes. As last-mile fiber optics-all the way to the customer premise-is still away, VDSL is a good alternative to enable high-bandwidth applications.

VDSL represents a distinct bright spot for the industry, with strong growth in both VDSL IC port shipments and revenue projected through 2008. As per In-Stat/MDR, this strong growth is driven by the increasing VDSL service deployments in Korea and Japan, as well as likely future deployments in North America, current deployments in Canada, and potential future deployments in support of fiber extension plans.

VDSL had at least five million connections by the end of 2004-mostly in South Korea, Japan, and China.

Global growth of DSL subscribers in 2004 was 35.5 million, to reach a total of 96.9 million in 2006.

Fastest growing regions were Middle East and Africa and Latin America, both at over 100%. At a global level, the growth rate was almost 58%.

European Union countries represent the largest regional DSL population in the world, followed by Asia Pacific, South and Southeast Asia, and North America.

In terms of technology, VDSL resembles ADSL to a large extent. But VDSL achieves data rates nearly ten times greater than those on ADSL.

ADSL employs advanced transmission techniques and forward error correction to realize data rates from 1.5 to 9 Mbps over twisted pair, ranging to 18,00 feet; VDSL employs the same advanced transmission techniques and forward error correction to realize data rates from 13 to 55 Mbps over twisted pair, ranging to 4,500 feet.

VDSL is suitable for a full-service network whereas ADSL may not be a full-service network technology but has the singular advantage of offering service over lines that exist today. For services like video conferencing, Internet access, video on demand, and remote LAN access-which can be delivered at speeds at or below T1/E1 rates-ADSL/VDSL offer a good combination for network evolution.

With line lengths shrinking-proximity to a central office or deployment of fiber based access nodes-ADSL and VDSL offer channels and capacity for services that require rates above T1/E1.

Minu Sirsalewala