V.92: The Final Chapter in the Never-Ending Story of Dial-up Modems
Ever since the first dial-up modems appeared in 1960s, many have repeatedly predicted their obsolescence. However, contrary to such predictions, dial-up modems actually thrived in the 80’s and 90’s as a result of slow roll-out of residential digital services, and the unprecented growth of Internet and remote access.
Since the first 300 b/s dial-up modem V.21, modem speeds increased steadily, most recently approaching download speeds of 56 kb/s in ITU Recommendation V.90, finalized in 1998. V.90 takes advantage of the direct-digital PCM network connection of an Internet Service Provider’s remote access server, to achieve such high downstream (from ISP to a user) speeds. However, for upstream transmission (from a user to ISP), V.90 employs the older V.34 technology which typically delivers 28.8 kb/s.
A new ITU modem standard called V.92 will increase upstream rates to above 40 kb/s, again taking advantage of PCM connections. In this paper, we present a new transmission scheme which is adopted in V.92. The proposed scheme is based on a generalization of Tomlinson-Harashima precoding.
As we predict that V.92 will be the last dial-up modem standard, we wonder whether we might be falling into the same trap that many others have fallen in the past. You can be the judge!
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