telecommunication Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

, a shared medium is a

medium Medium may refer to: Aircraft *Medium bomber, a class of warplane * Tecma Medium, a French hang glider design Arts, entertainment, and media Films * ''The Medium'' (1921 film), a German silent film * ''The Medium'' (1951 film), a film vers ...

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

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 highligh ...

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 ...

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 ...

, 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� ...

scheme divides up the

capacity Capacity or capacities may refer to: Mathematics, science, and engineering * Capacity of a container, closely related to the volume of the container * Capacity of a set, in Euclidean space, the total charge a set can hold while maintaining a giv ...

of the medium. Common multiplexing schemes include time-division multiplexing and

frequency-division multiplexing In telecommunications, frequency-division multiplexing (FDM) is a technique by which the total bandwidth (signal processing), bandwidth available in a communication channel, communication medium is divided into a series of non-overlapping freque ...

. 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, ...

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 short messages in fixed format, i.e. ''network packet, packets,'' that are transmitted over a digital Telecommunications network, network. Packets consi ...

, 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 traffic before transmitting on a shared transmission medium, such as an electrical bus or a band of the electromagnetic ...

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 mos ...

, etc.

Examples

DOCSIS Data Over Cable Service Interface Specification (DOCSIS) is an international telecommunications standard that permits the addition of high-bandwidth data transfer to an existing cable television (CATV) system. It is used by many cable televisio ...

GPON ITU-T G.984 is the series of standards for implementing a gigabit-capable passive optical network (GPON). It is commonly used to implement the link to the customer (the ''last kilometre'', or ''last mile'') of fibre-to-the-premises ( FTTP) serv ...

10BASE5 10BASE5 (also known as thick Ethernet or thicknet) was the first commercially available variant of Ethernet. The technology was standardized in 1982 as IEEE 802.3. 10BASE5 uses a thick and stiff coaxial cable up to in length. Up to 100 stat ...

References

Multiplexing {{Telecomm-stub