In general, broadband refers to telecommunication in which a wide band of frequencies is available to transmit information. Because a wide band of frequencies is available, information can be multiplexed and sent on many different frequencies or channels within the band concurrently, allowing more information to be transmitted in a given amount of time (much as more lanes on a highway allow more cars to travel on it at the same time). Related terms are wideband (a synonym), baseband (a one-channel band), and narrowband (sometimes meaning just wide enough to carry voice, or simply “not broadband,” and sometimes meaning specifically between 50 cps and 64 Kpbs).
Various definers of broadband have assigned a minimum data rate to the term. Here are a few:
Newton’s Telecom Dictionary: “…greater than a voice grade line of 3 KHz…some say [it should be at least] 20 KHz.”
Jupiter Communications: at least 256 Kbps.
IBM Dictionary of Computing: A broadband channel is “6 MHz wide.”
It is generally agreed that Digital Subscriber Line (DSL) and cable TV are broadband services in the downstream direction.
WHAT IS BANDWITH
1) In electronic communication, bandwidth is the width of the range (or band) of frequencies that an electronic signal uses on a given transmission medium. In this usage, bandwidth is expressed in terms of the difference between the highest-frequency signal component and the lowest-frequency signal component. Since the frequency of a signal is measured in hertz (the number of cycles of change per second), a given bandwidth is the difference in hertz between the highest frequency the signal uses and the lowest frequency it uses. A typical voice signal has a bandwidth of approximately three kilohertz (3 kHz); an analog television (TV) broadcast video signal has a bandwidth of six megahertz (6 MHz) — some 2,000 times as wide as the voice signal.