Communing at the speed of 'lite'

Jack Schofield

Three leading members of the computer industry, several United States-based telephone companies and two dozen other suppliers got together at last week’s ComNet conference in Washington DC to back a new communications standard that works 30 to 50 times faster than today’s modems.

The new system, called DSL Lite, also enables phone companies to offer a permanent Internet connection. This cuts out the modem dialling and the engaged tones while allowing normal voice calls to be made on the same line at the same time.

DSL Lite is being backed by the Universal ADSL Working Group, a megaconsortium that includes Compaq, Intel and Microsoft, phone companies like Bell Atlantic, US West and MCI, and manufacturers such as Texas Instruments, Rockwell and Alcatel.

DSL Lite is a form of “digital subscriber line”, which adds extra carrying capacity to the standard copper wire between the home and the telephone exchange by using modem-like devices called multiplexors at both ends to exchange high-frequency signals that are above the band used for voice calls.

The standard DSL system can handle downloads at six megabits per second, while DSL Lite manages 1,5 megabits a second. (Uploads are slower at 128 kilobits per second.)

Compaq has announced a deal with Ameritech, a US phone giant, to use the new system for high-speed Internet trials in several cities in the US. Compaq will sell computers already equipped to use the service, and Microsoft will add software support to its Windows 98 operating system.

The Ameritech DSL Lite service costs $150 to sign up and then $60 a month, which compares with $150 to $250 a month for DSL.

DSL first attracted attention in 1994 when it was proposed as a way for phone companies to deliver video signals and thus compete with cable television suppliers. Several tried the idea.

DSL does have problems. It uses a “splitter” to collect the signal at the house and split off the portion used for making voice telephone calls. The splitter requires installation and pushes up the cost. Worse, there are no interoperability standards for all the different DSL systems under development.

DSL Lite is an attempt to deal with these drawbacks. By leaving a clear separation between the voice and data channels it avoids the need for a splitter, though this is also why it is slower than normal DSL. Also, by uniting behind a single standard, the hardware, software and service suppliers hope to avoid the incompatibilities that have dogged DSL to date.

DSL Lite has advantages over rival systems such as ISDN (integrated services digital network) and cable modems attached to cable television networks. For a start, DSL Lite’s 1,5- megabits-per-second capacity is about 20 times greater than single channel ISDN, and like a cable TV network, DSL Lite provides a permanent connection.

Of course, all these speeds are theoretical when it comes to the Internet, which at peak times may not supply data fast enough to swamp a pair of tin cans and a bit of string. High-speed connections help, but at best they move the bottlenecks “upstream” to the Internet service provider’s connections, to the transatlantic cables, to the Internet’s backbone network, and ultimately to the servers that often struggle to dish up badly written, overcomplicated Web pages.

And although DSL Lite sounds like a winner, it still has a long way to go. DSL technology is heavily dependent on sophisticated error-correction software, and its capacity to carry data depends on the thickness of the telephone wire that is already installed, the distance to the nearest exchange, and even the number of connections in the wire. DSL Lite delivers data so fast that a PC’s standard serial port can’t cope, and while Intel reckons the Universal Serial Bus fitted to many new PCs will handle it, a network card may be required for older models.

But bear in mind that phone companies move much slower than computer companies. ISDN first appeared in 1986, and a decade later it should be so cheap and convenient that everyone uses it. Instead it’s still absurdly expensive and few people do. DSL could suffer the fate of ISDN and became obsolete before it is widely used.

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