Definition: Learn what bandwidth is and how the term is used as a synonym for signal frequency range, data transfer rate and capacity.

There are two frequently used definitions of bandwidth. 

1) In electronic communication, bandwidth is the range of frequencies that an electronic signal uses on a given transmission medium. This range is also referred to as the band and bandwidth literally describes 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. This meaning is the origin of the word bandwidth.

2) In computer networks, bandwidth is used as a synonym for data transfer rate, the amount of data that can be carried from one point to another in a given time period (usually a second). In this usage, bandwidth refers to the data rate that is supported by the network connection or the interfaces that connect to the network. This meaning of bandwidth is usually expressed in bits (of data) per second (bps). In general, a communication link with high bandwidth is one that may be able to carry enough information to sustain the succession of images in a video presentation without jitter or buffering caused by latency. It should be remembered that a communications path usually consists of a succession of links, each with its own bandwidth. If one link in the path is much slower than the rest, it is said to be a bottleneck.

When someone talks about how to calculate bandwidth with a bandwidth test, they are most likely discussing how to determine the highest possible reliable transmission rate for data transfer. This rate, which may also be called throughput, can be determined by measuring the time required for a file to leave its point of origin and successfully download at its destination.

3) In business, bandwidth is sometimes used as a synonym for capacity or ability. In this usage, bandwidth may include such things as budget, time, staffing or knowledge.

See also: spectrum efficiency, broadband, throttled data transfer, Shannon's Law

This was first published in August 2014

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