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December 15, 1996, Issue: 720
Section: The H-Report: Context -- Background news analysis
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Will ADSL Outpace ISDN In Telecom Race?
By Joe Rudich
Just as ISDN has won a smidgen of market credibility, it's running head-on into Asymmetric Digital Subscriber Line (ADSL)-a telco-promoted sibling sent to usurp ISDN's role as a fast data provider to telecommuters, Web users, small businesses and the networked masses.
The cudgel borne by ADSL is speed-which Greg Gapinski, broadband access manager for IBM's Global Network, says is up to 50 times greater than the external telecommunications rates now seen in most homes and small offices. ADSL lets users receive information from a host or service provider at a faster rate than the user can transmit. Motorola, one of the developers of this technology, has reportedly even bumped up those numbers to 640 Kbps and 9 Mbps, respectively, in private tests.
Since ADSL is still in the test phase, it's possible the rates will improve, just as analog modem speeds soared from 300 bps to 28,800 bps, and now 56-Kbps modems are hitting the market. It's also possible that once ADSL moves beyond the test phase, it won't live up to expectations.
It's especially likely that ADSL, typical of any huge leap in available bandwidth, is apt to expose a series of previously hidden bottlenecks-such as overloaded Web servers, Internet congestion and even Web browser limitations. Dave Bush, systems engineering manager for Motorola's ADSL team, says he believes, however, that such bottlenecks will be overcome quickly, especially with browser manufacturers primed to rev their products on an almost monthly basis.
Even so, the asynchronous nature of ADSL-illustrated by its ability to receive data faster than it can transmit-will always be better-suited for some applications than others.
ADSL also has distance limitations. In recent tests, only customers within about two miles of a central telephone office (which would include at least two-thirds of all homes in the United States) could obtain performance in the 4-Mbps to 8-Mbps range. Slower speeds of about 1.54 Mbps extend to the three-mile limitation now seen with ISDN.
Another ADSL disadvantage is that it is dedicated-unlike the more flexible, switched ISDN technology. This means ADSL is similar to T1 or 56-Kbps circuits and relies on packet switching to move data from location to location.
There also is contention between two modulation techniques for ADSL transmission, Carrierless Amplitude Phase (CAP) and Discrete Multitone (DMT). The American National Standards Institute (ANSI) has anointed DMT as a North American standard, and it is favored by manufacturers such as Amati Communications Corp., Aware and Motorola. CAP, however, remains the favorite of several telecommunications technology developers, including Alcatel Telecom, Lucent Technologies, Paradyne Corp. and Westell Technologies. CAP, in fact, is the technique used in Chicago-area trials involving Ameritech and IBM, which are by far the largest yet undertaken with ADSL. If a clear standard does not emerge, a user will need to verify that he or she is using the same type of ADSL as his or her service provider, online service or office in order to connect.
So what is there to recommend ADSL? Quite a bit.
l Even with bonded 128-Kbps ISDN, a telecommuter is apt to notice a discouraging difference when logging onto a centralized LAN from home versus the office. That's because 128 Kbps is barely 1 percent of the 10 Mbps provided by Ethernet (although this bandwidth is shared). But with 6-Mbps ADSL, downloading database information will be only a bit slower than working from the office. Remote users should finally find it comfortable to log in and run networked applications, not just transfer files and download e-mail.
l For offices now using ISDN between branches or other WAN nodes, ADSL's 6 Mbps offers a significant speed advantage. In such a scenario, it even competes with expensive 1.544-Mbps T1 lines. Of course, ADSL's pricing is yet to be determined. Ameritech, however, is charging field-test customers $200 per month per line. The first ADSL Internet service provider (ISP), InterAccess, charges a $200 monthly line fee; customers also pay a one-time $200 installation fee and $1,600 for the modem.
l ADSL is superior to ISDN when it comes to sharing lines. For example, if as few as six concurrent users tap a router to a single ISDN line for Internet access, the connection will be less responsive than if every user relies on a standard modem. The same number of people theoretically could share an ADSL circuit, with each experiencing T1-caliber performance.
Field Trials Today, ADSL is being proven in the field, with at least nine trials announced or already begun by regional Bell companies. None, however, will use more than 1,000 lines, making these trials a tiny base for testing or commercial expansion. Meanwhile, Chicago's InterAccess launched its own commercial ADSL offering this past September, and early market experiences will doubtless determine how rapidly ADSL wins acceptance.
Jennifer Tyrell, vice president of marketing at Aware, says: "1997 will be the year that ADSL becomes a viable commercial service, available in a significant number of areas. Initial costs may be higher, but the target price ranges for ADSL will need to approximate $300 to $600 for modems and $50 to $75 for monthly line charges." She adds that once the cost of ADSL drops to these levels, demand and availability for this technology will simultaneously mushroom by the beginning of 1998.
Although the mass market for Internet users has captured the imagination of ADSL promoters to date, ADSL may prove to be the high-speed communications technology best-suited to corporate needs. One reason is high-speed cable modems eventually will compete with ADSL for Internet access to the home. Catering to business may be a better bet-and the need for speed isn't going away. New analog modems that extend speeds to 56 Kbps have been announced by Cardinal Technologies, Microcom and U.S. Robotics (see "56-Kbps Modems Are In Search of a Home," November 15, page 24). But 56 Kbps is slower than 128-Kbps ISDN, which in turn is slower than ADSL.
Joe Rudich is an advanced technology analyst for Northland Insurance Co. in St. Paul, Minn. He can be reached at jrudich@interserv.com.
Copyright r 1996 CMP Media Inc.
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