What is ADSL? • ADSL stands for Asymmetric Digital Subscriber Line. • Modem technology that transforms ordinary phone into high-speed digital lines for ultra-fast internet access. • Use digital coding techniques to squeeze up to 99% more capacity out of a phone line without interfering with your regular phone services.
How Fast is ADSL? • ADSL provides speeds up to 8 Mbps downstream (i.e. downloads) and up to 1 Mbps upstream (i.e. uploads).
Why ADSL is much faster than a regular phone line connection? • V series modems are designed based on 4000 Hz voice grade bandwidth. • ADSL makes full use of the bandwidth of the physical connection between your home and the central office. • Phone cable bandwidth: • 1 MHz if < 2 miles • 300 KHz if between 2 - 3 miles
Benefits of ADSL • Simultaneous Internet and voice/fax capabilities over a single telephone line. • Uninterrupted, high-speed Internet access that's always on-line. • Cost-effective solution for residential customers, telecommuters and small businesses.
ADSL Modem • Inside Your PC: Your computer's ADSL modem connects to a standard analog phone line. • Voice and Data: A DSL modem has a chip called a POTS splitter, which divides the existing phone line into two bands: one for voice and one for data. Voice travels on the first 4kHz of frequency. The higher frequencies--up to 2MHz depending on line conditions and wire thickness--are used for data. • Split Again: Another chip in the modem, called a channel separator, divides the data channel into two parts: a larger one for downstream Internet data and a smaller one for upstream Internet data
ADSL Line Connection • Over the Wire: At the other end of the phone line--18,000 feet away at most--is another ADSL modem, located at the phone company's central office. This modem also has a POTS splitter, which separates the voice calls from the data. • Telephone Calls: Voice calls are routed to the phone company's public switched telephone network (PSTN) and proceed on their way as usual.
ADSL Line Connection (cont.) • Internet Requests: Data coming from your PC passes from the ADSL modem to the digital subscriber line access multiplexer (DSLAM). The DSLAM links many ADSL lines to a single high-speed asynchronous transfer mode (ATM) line, which in turn connects to the Internet at speeds up to 1Gbps. • Back at You: The data you request is retrieved from the Internet and routed back through the DSLAM and ADSL modem at the phone company's central office before coming back to your PC.
Key advantage of ADSL • The strength of ADSL compared to other high speed transmission alternatives (such as cable modems) lies in the number of existing telephone lines -- now approaching 750 million -- compared to new cabling which has reached comparatively few homes and almost no small businesses
ADSL Availability • Right now ADSL is available in only about one-third of the country. The top providers are on the coasts or in tech-centered states. • ADSL providers in Texas • ADSL Pricing: LavaNet
ADSL Future • DSL is an excellent technology for anyone needing high bandwidth, if you can get it and afford it. For the near future, DSL's high price is likely to restrict it to businesses and well-heeled enthusiasts. • Jupiter Communications predicts that 3% of U.S. homes with Internet access will use DSL by the year 2000.