Before V.90 was determined, three different types of PCM communication were being considered for determination. PCM modulations were enabled by digitally terminating the central site modems and limiting the number of analog conversions to one. This structural network change allowed modems to break the 33.6 Kbps barrier and come closer to the absolute maximum of 64 Kbps.

The first type of PCM communication, and the one that was eventually determined, was the method where PCM modulations were in the downstream direction, and QAM (V.34) modulations were in the upstream direction. The second, labeled V.90 Issue 2, was PCM upstream, where PCM modulations were in both the upstream and downstream direction. The third, which is still pending, though with almost no support for moving forward, is PCM end-to-end, which allows two client modems to use a PCM modulation.

There was very little support for V.90 Issue 2 because of its limited utility. To make it more attractive, papers were presented at the August 1999 TIA meeting that proposed an expansion of the features of a next generation modem standard. These papers proposed two additional features. The first additional feature was dubbed quick connect and provides a standard method to shorten the negotiation time by storing line parameters in the client. The quick connect method reduces the negotiation time from over 20 seconds to about 10 seconds. The second additional feature is a Modem-on-Hold™ (MOH) feature. This codifies a method for the central site modem to request the client modem to go on hold, or vice versa, and is a mechanism whereby call-waiting tones can be better survived by voice-band dial-up modems.

Quick connect; MOH and PCM Upstream are supported in V.34 mode. Product release dates will differ by manufacturer and product type. You can view a list of V.92 modem suppliers here. Historically, new communication standards are made available in client modems before the network modems, and this will be the case with V.92. Industry-leading network equipment companies have tested V.92 and a number of ISPs have V.92 ports available. Of course, not all ISPs will upgrade to V.92 at the same time. You can email your ISP and ask them when they will launch the new standard.

While much of the industry interest is in broadband DSL and Cable connection, for the next five years, the majority of connections to the Internet will still be via standard dial-up modems. As the next-generation modem standard, V.92 focuses not on speed, but on ease of use and better functionality. Increases in speed are indeed provided through PCM Upstream. MOH and quick connect can approximate the always-on and simultaneous voice and data functions of broadband. Modems that have these features provide a better user experience when connecting to the Internet.

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