DSL, in its many manifestations, allows telcos to offer broadband multimedia access to the Internet over legacy twisted copper pairs used for the telephones.

Asymmetric Digital Subscriber Line (ADSL)---one of the DSL versions---transforms the twisted copper pairs of telephone wires into high-speed digital lines to deliver data at substantially faster speed and meet the demands of the new broadband multimedia services: up to 8 Mbps from the network to the customer (downstream rate), and up to 1Mbps from the customer back to the network (upstream rate). ADSL is thus 150 times faster than modems (at 56 Kbps) and 70 times faster than ISDN (at 128 Kbps).

This technology allows data and voice transmission to take place simultaneously on single telephone line, abolishing the need for dial-ups, the attendant charges and time delays. Thus it enables the user to be constantly online—an ‘always on’ connection to the Internet. Being able to instantly send and receive information in 'real time’ means international business-to-business communication can occur without the customary time-constraints, making it attractive to business users.

A dedicated digital circuit between one’s home or office and the telephone company’s central office (CO) ensures a high degree of security. With DSL, one can talk on the phone or send fax at the same time while surfing the Internet—all on one phone line.

DSL’s big advantage is lower entry costs---as compared to fiber, cable modem and wireless network technologies---to build the ‘last-mile’ bridge to its customers. The last mile—or local loop—is a notorious bandwidth bottleneck, and traditional copper telephone lines are generally the only readily available solution for reaching most of the users.

Equipment costs for setting up ADSL are continuously falling as the volumes are building up. This makes it particularly attractive for small to medium-sized enterprises (SMEs) and the small office-home office (SOHO) market segments which cannot always afford the cost of installing other high-speed solutions.

The family of DSL standards comprises HDSL, SDSL, ADSL and VDSL. Recently, the International Telecommunications Union (ITU) decided on a new standard for DSL, called ‘G. lite’, also known as ‘ADSL lite’.

ADSL Lite or G.lite (ITU’s G.992.2 standard) is the simpler ‘trimmed down’ plug-and-play entry-level version and already computer manufacturers are building ADSL-ready computers for G.lite. G.lite offers lower speeds (of up to 1.5 Mbps downstream and 384 Kbps upstream) than full rate ADSL, but it can provide the service over longer distances to meet the needs of consumers located far from a telephone exchange.

ADSL Forum is focusing on its mass scale deployment. G.lite is specifically tailored for the consumer market segment not only because of its lower cost but also due to its simple on-site installation. The telco’s CO switch, however, must support G.lite and the consumer must still be within the distance limitation. It is however advisable for telco’s CO equipment to be rate-adaptable and to have capability to cater for G.Lite version as well.

Asia-Pacific region has always been at the forefront of DSL technology and its advancement. From Hong Kong to Singapore, Japan to Australia, New Zealand to Taiwan, Korea to China, trials, pilot programmes and full-scale services are coming on stream.

Singapore Telecom (SingTel) has deployed over 10,000 ADSL lines carrying speeds of 8 Mbps downstream and 1 Mbps upstream to produce video, as well as high-speed Internet and data access to customers using an ATM-based ADSL solution. SingTel’s Magix---the Internet service access arm---started to offer high speed Internet access using G.lite in December 1998.

HongKong Telecom (HKT) started to roll out its ADSL service for video-on-demand in July 1997. HKT’s SuperNetvigator 1.5 Mbps Internet access service reportedly uses a hybrid DSL/ATM architecture to bring broadband to residential homes. The service leverages off HKT’s ATM backbone and uses DSL in-building. Chunghwa Telecom in Taiwan is trialling the service for near video-on-demand and remote access applications in Central Taipai. Meanwhile, in China, Guandong PTA expects to offer rate adaptive ADSL over 4,000 lines by the end of 1999. Speeds of 4 Mbps downstream and 128 Kbps upstream have also been tested by Korea Telecom in six cities, including Pusan.

DSL is specially suited for in-building high-speed networking on legacy cabling. Usually, to make office towers, hotels and residential high-rises broadband-capable, the legacy wiring in the building had to be replaced with Ethernet cabling/ports. Instead of that, one can now install a DSL access concentrator and DSL modems in the customer premises and offer broadband networking over-in building wiring. In highly dense geographical areas such as Singapore and Hong Kong with high-rise office towers, DSL is easily deployable inside the building.

In the U.S., the hotel industry has successfully used in-building DSL. To offer high-speed Internet connections to business travelers, leading hotel chains such as Marriott International are turning to DSL. Sheraton Hotels, is starting use of ADSL technology to raise guest services standards in the Asia-Pacific region and offer its guests a whole new generation of in-room multimedia services. Because they own the cabling infrastructure, hotel management can introduce DSL broadband services to their customers without having to rewire the whole building. All they need is enough bandwidth out of the building to an external ISP or central office switch to support the extra bandwidth demand. A building with say 10 office units, each with a 6 Mbps ADSL service---needing a total of 60 Mbps of bandwidth---may be provided a bandwidth of a quarter of 60 Mbps i.e. 15 Mbps, going out of the building.

The estate developers need to plan the whole data network and even set up a local portal with tailored content---including for advertising---for residents of the complex. Not only will this type of portal have a niche market, the developers can effectively set up a mechanism to capture the value-add transactions that will grow with the emergence of e-commerce applications.

Due to enormous growth of Internet and bandwidth hungry applications, the demand for higher network access speeds has never been greater needing big bandwidth pipes. With a DSL, service provider can build a robust, ubiquitous broadband network that could run at multi-megabits per second of speed and deliver value-added applications to customers’ desktops which now come with Gigabytes of memory.

Since DSL provides high bandwidth at a reasonable cost, small business e-commerce opportunities could take off, along with new opportunities for ISPs to provide imaginative services for new online entities.