bandwidth

bandwidth
1. of a transmission channel. A measure of the information-carrying capacity of the channel, usually the range of frequencies passed by the channel. This will often consist of a single passband, but may instead consist of several distinct (nonoverlapping) passbands. Each passband contributes to the bandwidth of the channel a quantity equal to the difference between its upper and lower frequency limits; the sum of all such differences plus necessary guard-bonds gives the total bandwidth required.

In these cases bandwidth is measured in frequency units, i.e. hertz (Hz). If the bandwidth is considered in a transform domain other than frequency (such as sequency) then it is measured in the appropriate units. In defining channels and filters in the frequency domain, bandwidth, unless otherwise defined, is assumed to be the frequency range between the points at which the frequency response is 3 decibels lower than the passband frequency and is sometimes known as the half-power bandwidth.

See also band-limited channel, channel coding theorem (for Shannon–Hartley law), Nyquist's criterion.

2.. A measure of the rate of transfer of digital information, usually expressed in bits or bytes per second.

3. See band matrix.