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At one time, everyone thought that 28.8K and 33.6K would be the end of the line. The main problem is the disturbance of the analog telephone lines. To get higher speeds, you'd need radically different modems that wouldn't work over standard phone lines.
The advent of 56K modems has changed all that. You can now have a faster connection using your existing phone lines and new modems that work just like your old modem, only faster. The nature of 56K technology is a little different than existing analog modems. In particular, it depends on a half-digital connection to achieve its higher speeds. Because of the lager number of digital lines, the disturbance still exists but at a lower level so it has become possible to transfer data with a maximum speed of 56 kbps. | ||||||||||
| Evolution of the 56K Standard: | ||||||||||
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In September 1996, 3Com was the first company to submit a proposal to the ITU calling for a 56K recommendation. The work toward a standard began in North America within the ITU's Telecommunications Industry Association (TIA) committee, and in April, 1997, the ITU officially set up a rapporteur's group with the goal of determining an international 56K standard as quickly as possible. On December 5, 1997 in Orlando, the working party agreed to a compromise on the two remaining technical issues, virtually assuring a standard determination at the January/February 1998 ITU meeting. At the February meeting in Geneva, Switzerland, the 56K standard specification was determined and given its official V-series number - V.90. The technical aspects of a determined standard were thereby frozen, although there may be subsequent editorial changes. At its September 1998 meeting, the ITU will complete the formalities at which time the determined 56K recommendation becomes a "decision," also referred to as ratification. | ||||||||||
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To understand 56K, it's necessary to take a brief look at how traditional analog modems work. Information inside your computer is in digital format: all of the data is stored as 1s and 0s. Normal phone lines are analog: they transmit data as a series of peaks and valleys. The "modem" is a MOdulator/DEModulator: it modulates outgoing data from digital to analog, and demodulates incoming data from analog to digital. Above a certain threshold (called Shannon's Limit) the signal-to-noise ratio of any medium becomes too low to reliably transfer data. The analog phone line is the limiting factor in the speed of data transmission because of the inherent noise it contributes. Today's telephone network is increasingly digital. In particular, the portion of the phone connection between the phone company and the Internet Service Provider (ISP) is often digital. Digital lines still have noise, and are still subject to Shannon's limit, but they have less noise and a higher ceiling. Several companies have created techniques that take advantage of the digital portion of the phone network to achieve higher speeds than were possible with a purely analog pathway. These new techniques treat the phone system as a mostly digital network that just happens to have an analog portion. There are several consequences to the reliance on a half-digital connection. Your Internet service provider (ISP) must have digital phone lines to the public switched telephone network (PSTN). That's the easy part: if your ISP offers 56K, they've got the digital lines. | ||||||||||
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