telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

, a shared medium is a

medium Medium may refer to: Science and technology Aviation *Medium bomber, a class of war plane *Tecma Medium, a French hang glider design Communication * Media (communication), tools used to store and deliver information or data * Medium of ...

channel Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Austral ...

information transfer In telecommunications, information transfer is the process of moving messages containing user information from a source to a sink via a communication channel. In this sense, information transfer is equivalent to data transmission which highlights ...

that serves more than one user at the same time. In order for most channels to function correctly, no more than one user can be transmitting at a time, so a

channel access method In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. Examples of shared physical med ...

must always be in effect. In

circuit switching Circuit switching is a method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel ( circuit) through the network before the nodes may communicate. The circuit guarantees the full b ...

, each user typically gets a fixed share of the channel capacity. A

multiplexing In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - a ...

scheme divides up the capacity of the medium. Common multiplexing schemes include

time-division multiplexing Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fracti ...

and

frequency-division multiplexing In telecommunications, frequency-division multiplexing (FDM) is a technique by which the total bandwidth available in a communication medium is divided into a series of non-overlapping frequency bands, each of which is used to carry a separate ...

. Channel access methods for circuit switching include

time-division multiple access Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, o ...

frequency-division multiple access Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing ...

, etc. In

packet switching In telecommunications, packet switching is a method of grouping Data (computing), data into ''network packet, packets'' that are transmitted over a digital Telecommunications network, network. Packets are made of a header (computing), header and ...

, the sharing is more dynamic — each user takes up little or none of the capacity when idle, and can utilize the entire capacity if transmitting while all other users are idle. Channel access methods for packet switching include

carrier-sense multiple access Carrier-sense multiple access (CSMA) is a medium access control (MAC) protocol in which a node verifies the absence of other Network traffic, traffic before Transmission (telecommunications), transmitting on a shared transmission medium, such as a ...

token passing On a local area network, token passing is a channel access method where a packet called a ''token'' is passed between nodes to authorize that node to communicate. In contrast to polling access methods, there is no pre-defined "master" node. The most ...

, etc.

References

Multiplexing {{Telecomm-stub