 |
|
|
page 6 of 7
Washington's
Bogeymen
For
that reason the future of the American computer industry largely depends
on the future of the cable industry. By linking America’s computers
to broadband networks and then to telco fiber systems, cable can be the
great enabler of the next phase of development in America’s digital
economy.
In laying broadband systems the cable industry has already been forced
to solve many of the key problems of an information superhighway. Although
often depicted as an intrinsically one- way service, cable technology
has, in fact, long provided two-way capabilities.
Every cable coax line, for example, offers potential bandwidth equivalent
to six times the 160 megahertz of spectrum assigned by the FCC for personal
communications services. Cable can accommodate as much as one gigahertz—a
billion cycles per second—of communications power. This is some 250,000
times the capacity of a four-kilohertz telephone line to the home. Just
one six-megahertz cable channel commands 1,500 times the bandwidth of
a telephone line. In every coax connection the first four channels, between
five and 30 megahertz, are reserved not for broadcast but for reverse
communications to the headend. Widely used to transfer video programming
among headends and satellite dishes and other programming sources, these
channels alone already represent a potential information highway for home
computers 2,500 times faster than a 9,600-baud modem to a phone line.
Even these possibilities, however, underestimate the potential of cable.
The coax laid by the cable firms must carry analog video material without
interference or distortion. This means cable equipment must track perfectly
all the analog waveforms representing the shape and brightness of the
image, and must detect tiny differences in the frequencies of FM signals
bearing color and sound information. Because any deviation in an analog
wave imparts a defect to the picture, cable TV has had to develop extremely
low loss technologies. Although most current cable systems function at
much lower signal-to-noise ratios, measured logarithmically, a cable TV
plant can potentially function at nearly 50 decibels, or at a signal-to-noise
power ratio of almost 100,000-to-one.
Necessary to transmit high-quality analog video, between 10,000- and 100,000-to-1
signal-to-noise ratios are vast overkill for the relatively crude on-off
codes of digital communications, which can function at 17 decibels or
less. Therefore, the one- gigahertz coax lines can carry many more than
one bit per hertz. Craig Tanner, vice-president of advanced TV projects
at Cablelabs, the industry’s research arm in Louisville, Colo., estimates
that by wiggling every wave in readable patterns using a modulation scheme
called 256 QAM (quadrature amplitude modulation), cable systems can transmit
as many as seven bits per hertz. This means that the one-gigahertz bandwidth
of an existing cable line might potentially carry between six and eight
gigabits per second, or more than three gigabits per second each way.
These potential links to homes are more capacious than the current telephone
fiber lines that accommodate tens of thousands of phone calls among telco
central offices.
This bandwidth represents the real potential of cable coax. For the next
decade much of the cable plant will still be devoted to analog TV broadcasts
or to digital renditions of pay-per-view movies. Time Warner’s Orlando
project, however, envisions devoting the top 350 megahertz of its system
to two-way digital communications, including 100 megahertz for the personal
communications services of wireless telephony and 150 megahertz for digital
two-way data flows. At a very conservative estimate of two bits per hertz,
Time Warner projects a total of 300 megabits per second from these digital
channels. At these levels a computer could download a full movie of two-and-a-half
hours in about one minute.
Cable's Real Potential is Not TV
Abandonment of the Malone model by Malone and the rest of the cable industry
ultimately requires that cable TV magnates develop a new grasp of the
dynamics of the microcosm: the exponential growth of computer power and
connections. Accustomed to the role of propagating mass entertainment,
cable leaders have long downplayed the potential market in computer communications.
Gradually growing throughout TCI, Time Warner, Continental Cablevision,
Jones Intercable and other cable firms, however, is a recognition that
the real future of cable is in computers rather than TVs. As David Fellows
of Continental declared in launching his pioneering new Internet access
system in Boston In late February, “The market for computer communications
is huge.”
Indeed, during the next decade the cable companies are going to discover
that the computer market for their services is far more important than
the television market. The computer industry, hardware and software, is
already some 60 percent larger than the television and movie industries
put together and is growing six times as fast. On-line networked computer
services, such as Prodigy, CompuServe, Delphi and America Online, are
collectively growing at a pace of close to 100 percent per year. When
on-line services can exchange video and audio files as readily as they
transfer text today, these computer networks will be able to outperform
any television system. Against all their expectations and plans, cable
executives are going to find themselves a central part of the computer
networking industry.
As Fellows explains, “Cable and computer network topologies go together
perfectly. Both provide shared bandwidth. Ethernet over cable is a natural.”
In both networks all the data flow by every terminal. The receiver tunes
into the desired channel. For computers, cable offers the dumb bandwidth
that is increasingly needed as terminals gain near-supercomputer powers.
In the past networks had to be smart in order to provide needed services
to the dumb terminals on their periphery, whether phones, computers or
TVs. Dumb terminals could tolerate narrowband connections. In the future,
however, all terminals will command supercomputer powers.
|
