Testing VDSL Circuits

What is VDSL?

VDSL stands for Very High Speed Digital Subscriber Line and offers a much faster transmission of data than standard DSL lines. It is delivered via a pair of copper lines twisted together to make a single line.

What's so different about VSDL?

VDSL is deployed over ordinary phone lines, which makes it a much cheaper option for upgrading than fibre optics or new experimental methods that require power lines.

VDSL2 looks promising with possible bandwidths of up to 30MHz that will enable data transfer rates of up to 100Mbps for both up and down streaming.

This has some exciting prospects for high quality video, such as HDTV, on the Net. In addition, the seven different frequency bands used by VDSL means users can customise their upload and download rates.


The existing ADSL and ADSL2+ broadband services have fixed bit rates for downloading and uploading, and cannot support high definition video because of bandwidth limitations. VDSL does not have these limitations and, understandably, VDSL2 has a much greater range than VDSL1. However, ADSL still performs better, in terms of how far away a computer is from a telephone exchange before the service is seriously compromised or unavailable, and is more cost-effective for the average user.

One downside is that while VDSL2 could start with a theoretical maximum of up to 250Mbps (if the computer was inside the telephone exchange), it quickly drops to 100Mbps if the computer moves just half a kilometre away. At one kilometre the rate halves to just 50Mbps. ADSL2+ matches the performance of VDSL if the computer moves to just 1.6km away from the telephone exchange.