V.34 Versus V.32Terbo

While standards continue to be worked out for high-speed modems, their potential benefits are clear. Faster transmission times mean direct cost savings if you regularly transmit data via modems. What payback can you expect from high-speed modems? One way to gauge this is to compare sample costs when sending a large file at the speed of the fastest V.34 and V.32terbo modems we tested. A 1-MB file sent from New York to San Francisco at 7400 bytes per second (the tested speed of the Hayes Optima V.34 modem) takes approximately 2 minutes, 25 seconds. At a telephone rate of $1 a minute, the transmission costs $2.25. The same call at 4600 bytes per second (achieved by Zypcom's Z32t-SX V.32terbo modem) would cost $3.60.

Does this mean you should automatically choose the faster technology? In a year, the answer to this may be an unequivocal "yes," but until the V.34 standard is formalized, you should make your modem choice cautiously.

V.32terbo represents a relatively simple change to the V.32bis (14.4 Kbps) standard, and, as such, V.32terbo may best be viewed as an enhancement to V.32bis rather than as a competitor to V.34.

V.34 is a more radical change than V.32terbo, and it attempts to push modem speeds to their practical limits on voice-band lines. Besides speed, V.34 is innovative in its ability to "probe the channel," or select the best techniques for optimum performance along the telephone line.

In our throughput tests over clean and impaired lines, we saw more consistent performance from the V.32terbo modems. By contrast, the V.34 modems we tested seemed a bit "green." They often required firmware updates or undocumented escape-code patches to coax them through our tests.

Many companies selling V.34 modems claim upgradability to the formal standard. This could range from a minor firmware code revi sion to a major board replacement.

Once V.34 is adopted, V.32terbo may survive by occupying a price point below the 28.8-Kbps products. Until then, V.34 may be the best choice for applications where you control both sides of the connection. When you control only one side, your best bets are probably a V.32terbo modem or a tried-and-true V.32bis modem.

THROUGHPUT* TRANSMISSION

CLASS DCE RATE AVERAGE PRICE (BYTES PER SECOND) COSTS**

V.34 28.8 Kbps $580 7413.4 $2.25

Comments: Fast, but firmware remains "green." Standard promises innovations beyond raw speed. Ease for upgrading to formal V.34 standard is a question mark.

V.32terbo 19.2 Kbps $452 4618.1 $3.60

Comments: Slower, but more reliable in current incarnation, thanks to protocol existing for almost two years. Firmware is established, and test sample showed few bugs.

* Based on fastest modems in our performance tests.

** Based on 1-MB file with phone rates at $1 per minute.