A communication channel is used to transport an information signal, such as a digital bit stream, from one or several senders (or transmitters) to one or several receivers. The capacity of a channel to transmit information is measured by its bandwidth in Hertz or its data rate in bits per second.
The pathways used to communicate data or communication channels, use two types of media:
• A physical transmission medium such as a wire, or cable (twisted-pair wire, coaxial cable, and fiber-optic cable).
• A logical connection or broadcast over a multiplexed medium (microwave, satellite, radio, and infrared). The multiplexing divides the capacity of the communication channel into several logical channels, one for each message signal or data stream to be transferred.