A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several senders to one or several receivers. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second.
Communicating an information signal across distance requires some form of pathway or medium. These pathways, called communication channels, use two types of media: Transmission line (e.g. twisted-pair, coaxial, and fiber-optic cable) and broadcast (e.g. microwave, satellite, radio, and infrared).
In information theory, a channel refers to a theoretical channel model with certain error characteristics. In this more general view, a storage device is also a communication channel, which can be sent to (written) and received from (reading) and allows communication of an information signal across time.
Examples of communications channels include:
A connection between initiating and terminating communication endpoints of a telecommunication circuit.
A single path provided by a transmission medium via either
physical separation, such as by multipair cable or
separation, such as by frequency-division or time-division multiplexing.
A path for conveying electrical or electromagnetic signals, usually distinguished from other parallel paths.
A data storage device which can communicate a message over time.
The portion of a storage medium, such as a track or band, that is accessible to a given reading or writing station or head.
A buffer from which messages can be put and got.
In a communications system, the physical or logical link that connects a data source to a data sink.
A specific radio frequency, pair or band of frequencies, usually named with a letter, number, or codeword, and often allocated by international agreement, for example:
Marine VHF radio uses some 88 channels in the VHF band for two-way FM voice communication.