Zeros and Ones - Video Voice and Data Requirements Over Fiber

If all pulses look the same, what's the difference between video, voice, and data? Theoretically, there is no difference. But each requires special skills on the part of providers. Voice, for instance, does not require much bandwidth; 100 Kbps per second will carry a high-quality phone conversation over Ethernet. A regular "analog" phone line uses as little as 8 Kbps. But the voice signal must be very clean, with no noticeable delay and no static. That's difficult to do on a network such as the Internet, which is used for many purposes at the same time.

Technical people thus describe voice as requiring a high QoS (quality of service and low bandwidth). Telephone service over digital data networks is called VoIP for Voice over Internet Protocol.

Video also requires good QoS, but not as good as voice. Small delays and a bit of static will often go unnoticed by viewers. But video requires a lot of bandwidth - 2 Mbps for standard-definition TV, and 4 to 8 Mbps (and as much as 20 Mbps) for the new high-definition TV, or HDTV.

But the video world is changing. Part of that change is already obvious: Cable companies are offering video on demand, or VoD. To deliver, they have to send extra signals down the coax, to individual customers. This increases the need for high quality service.

Today, almost all of those signals arrive as RF (radio frequency or analog) signals. Even when the signals move over fiber, they are often treated as if they are RF.

This is changing. The new technology is IPTV. In IPTV, the video moves as data, using the same Internet Protocol (hence IP) as any other data. As IPTV develops over the next few years, expect thousands, even hundreds of thousands, of channels, mainly sending video on demand to consumers who will be able to view the video on computers or portable devices (think iPODs) as well as on conventional TV sets.

Satellite TV vendors, who now count almost a fourth of American households as subscribers, cannot directly compete with VoD, because they can only send signals one way - from satellite down to subscribers.

Data is requiring more and more bandwidth to meet consumer needs, although 1 to 5 Mbps is typical. QoS needs are not as great as for voice or video, because the Internet Protocol automatically splits up data streams into "packets" each containing many thousands of zeros and ones, and reassembles them when they arrive at their destination. They do not have to arrive at the same time, as long as they arrive within a short period - typically a few fractions of seconds but sometimes much more.

Providers of all of these services have been used to thinking about consumers' bandwidth needs as asymmetrical. That is, the bandwidth has to be higher in one direction (the inbound direction to consumers) than the other. Few consumers create video now, for instance, but almost all view it from elsewhere.

Likewise, most users download more data than they upload. But those patterns have been changing. In much of Europe, where providers have offered symmetrical bandwidth, users have tended to upload more data, and even to create their own video.