In telecommunications and computer networking, a communication channel or 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. A channel is used to convey an information signal, for example a digital bit stream, from one or several senders (or transmitters) 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 data from one location to another requires some form of pathway or medium. These pathways, called communication channels, use two types of media: cable (twisted-pair wire, cable, and fiber-optic cable) and broadcast (microwave, satellite, radio, and infrared). Cable or wire line media use physical wires of cables to transmit data and information. Twisted-pair wire and coaxial cables are made of copper, and fiber-optic cable is made of glass.Digital channel models[edit]In a digital channel model, the transmitted message is modelled as a digital signal Examples of digital channel models are:

Binary symmetric channel (BSC), a discrete memoryless channel with a certain bit error probabilityBinary bursty bit error channel model, a channel "with memory"Binary erasure channel (BEC), a discrete channel with a certain bit error detection (erasure) probabilityPacket erasure channel, where packets are lost with a certain packet loss probability or packet error rateArbitrarily varying channel (AVC), where the behavior and state of the channel can change randomlyAnalog channel models[edit]In an analog channel model, the transmitted message is modelled as an analog signal. The model can b

e a linear or non-linear, time-continuous or time-discrete (sampled), memoryless or dynamic (resulting in burst errors), time-invariant or time-variant (also resulting in burst errors), baseband, passband (RF signal model), real-valued or complex-valued signal model. The model may reflect the following channel impairments:Types of communications channels[edit]Digital (discrete) or analog (continuous) channelBaseband and passband channelTransmission medium, for example a fibre channelMultiplexed channelComputer network virtual channelSimplex communication, duplex communication or half duplex communication channelReturn channelUplink or downlink (upstream or downstream channel)

Broadcast channel, unicast channel or multicast channelhese are examples of commonly used channel capacity and performance measures:

Spectral bandwidth in HertzSymbol rate in baud, pulses/s or symbols/sDigital bandwidth bit/s measures: gross bit rate (signalling rate), net bit rate (information rate), channel capacity, and maximum throughputChannel utilizationLink spectral efficiency