Multimedia Engineering

Understanding "bandwidth" is an essential factor in making intelligent choices in today's world of telecommunications services and products. Ferociously abused by the unschooled, "bandwidth" exceeds "digital" as the technology word most misunderstood and as a result, misused, term to come down the pike since Henry Ford made his first automobile and "mass-production" became the term to abuse. Although popularized by Ford's assembly line dynamics, mass-production can be traced to the shipbuilders of Venice several hundred years earlier.

Long before the world of digital electronics became mainstream, long before personal computers and the internet become common, "bandwidth" was a term engineers and scientists relied on to specify the numerical difference between the upper and lower frequencies of a section of the electromagnetic spectrum. Often this referred to a section designated for a specific application like radio broadcasting, but could also mean, e.g. the "visible spectrum" of light or the area of frequencies known as "gamma-rays." In this respect, "bandwidth" has no dependence on the speed that the signal(s) under consideration travel. All electromagnetic energy moves through a perfect vacuum at the speed light does, even if the signal is not at light frequencies. In the near vacuum of space, these speeds are near the speed of light. In the atmosphere, they slow down a little due to atmospheric conditions, but in that case and in wires and circuit boards we still consider these speeds to be very nearly the speed of light. This is why there is no discernible delay in analog electronics unless engineers provide long signal paths using mechanical and/or electronic methods. Comprehension of the meaning of bandwidth is quite difficult in the analog world without also understanding the relationship between frequency and period of a sinusoidal waveform, knowledge of which would help when considering that the bandwidth allocated for a conventional television broadcast signal is wide enough to accommodate 30 conventional FM radio broadcast signals.

The misunderstanding of the term "bandwidth" really began as the internet became commonplace towards the end of the last century. In an effort to promote "fast" connections to information, marketing folk kind of perverted the notion that somehow the terms "digital bandwidth" and "digital throughput" were interchangeable. They are not. Generally, "bandwidth" in the digital domain means the capacity of a digital transmission over an electronic pathway and is measured in bits per second. The speed of this transmission, also measured in bits per second, varies depending on conditions, mainly demand. The difference in terms is easy to understand. The pathway can support a maximum rate of transmission, but that doesn't mean all information over that path is traveling at that maximum rate.. For example, a cable modem service may provide you with 12 Megabits per second capability, but overloaded servers, overloaded routers, and overloaded shared connections contribute to the slowing of the information you wish to retrieve. "Throughput" is a term that reflects the amount of work the system is actually achieving over any specific amount of time. Why the marketing people don't refer to "maximum achievable bandwidth" as bandwidth and "actual data speed" as throughput is a mystery.

It is important to note that a digital transmission modulated (mixed) onto an analog carrier (e.g. digital television) is still an analog transmission the bandwidth of which is measured in Hertz (Hz.)(cycles per second) like any other analog transmission. The digital bandwidth of the data stream is a separate quantity and is expressed in bits per second.