SAN FRANCISCO (06/15/2000) - Once upon a time, everyone thought that digital subscriber lines would carry digital interactive TV. Not much came of that, but today DSL is the fastest-rising star in broadband Internet access.
The next destiny for this flexible pipe: voice.
Several firms are working to bring that service to homes and small businesses.
Since early this year, Mpower Communications has delivered Voice over DSL (VoDSL) services across the United States. In April, Picus Communications launched services in Washington, D.C., and Virginia. By the end of the year, more than a dozen other competitive local exchange carriers (CLECs) are expected to roll out VoDSL services aimed at the small business market.
VoDSL will be useful to a small business that needs multiple phone lines and broadband Internet access, but can't afford to spend upward of US$1500 monthly for T1 lines. With VoDSL, a 768 kilobits-per-second DSL line can be split into 2 to 16 virtual phone numbers. Each subtracts only 32 kbps from shared data bandwidth. Thus, a typical 8-line system would leave around 500 kbps for data.
Depending on the number of phone lines and additional services, prices could range from $200 to $600 monthly. VoDSL providers can keep the bills low because they install a single line, reducing labor and copper costs. In addition, they pay access fees to the local carriers for only one line per business instead of a dozen or so.
Carriers Get Ready
Getting VoDSL requires having a special gateway in a DSL-equipped central office and an integrated access device at the customer premises. The device links office telephones and provides Internet access to PCs via Ethernet.
Most major telecom players, including AT&T Corp. and WorldCom Inc., are testing the technology. Incumbent local exchange carriers (ILECs), which are local telephone companies such as SBC Communications, plan to offer consumer and small business products by the fall.
A recent TeleChoice study projects 40,000 DSL lines will be used for VoDSL by the end of 2001, rising to 100,000 lines by the end of 2001 and 1.75 million through 2004.
VoDSL gateways under development promise to support as many as 24 lines and run at 1.5 megabits per second in each direction.
New Technology Stokes ATM-IP Wars
VoDSL vendors and providers want to offer more than just a bargain-basement alternative to T1. They're working on such advanced services as prioritizing bandwidth, universal messaging, multimedia messaging, and dynamic provisioning, which is the capability to easily add or subtract voice lines for seasonal peaks. Mpower already offers some advanced services through technology developed by TollBridge, which relies in part on VoIP technology.
"IP allows us to integrate our offerings a lot easier, and it's substantially more cost-effective and cost-efficient," says Rolla Huff, Mpower's chief executive. The immediate advantage is dynamic bandwidth allocation. "If there are a lot of lines being used, the net speed can come down," Huff says. "As you start hanging up phones, the bandwidth increases."
Most vendors, however, depend upon the asynchronous transfer mode (ATM) standard that's part of telephony and DSL infrastructure. ATM boosters promise greater compatibility with standard telephony functions and equipment, as well as reliable service quality. The TollBridge technology requires 64 kbps per phone number for suitable voice quality. But ATM products need only 32 kbps.
Also, several ATM solutions support dynamic bandwidth to some degree.
In the long term, ATM solutions probably won't match the flexibility of pure IP. But for now, ATM has some nifty tricks, using software-only controls and switches.
MCI WorldCom is evaluating Switched VoDSL. It may link VoDSL clusters not only with the Internet and public phone network but also directly with corporate and long-distance networks. For the customer, this makes it easier for MCI WorldCom to bypass the local exchanges and duck fees, keeping costs down.
Software switches "provide a significant cost savings when you start to link large networks," says Sima Vaisman, vice president of product management at Accelerated Networks.
Soon, more and more IP applications will run on top of ATM. IP will gain ATM-like features, and the lines between the camps will blur, experts say.
"Eventually everything will be [VoIP], but by that time Voice over IP will look like ATM," Vaisman says.
Home, Sweet VoDSL?
While VoDSL migrates upward from small businesses into corporate networks, it's also likely to play a role in the home using ADSL. SBC plans to feature VoDSL in Project Pronto, a three-year, $6 billion project to make DSL available to 77 million customers. BellSouth plans to begin VoDSL trials this summer. Although the telcos are targeting two- to four-line systems for small and home offices, with the growing popularity of wireless phones, VoDSL's impact on consumers may be limited.
What's more, competition from another front could also push down prices. AT&T and the cable companies are exploring similar cable-oriented multiline services. Multiline cable telephony competition could force telcos to drop prices for low-end VoDSL and eventually leave plain old telephone service in a backup role.