In
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 tha ...
, a shared medium is a
medium or
channel of
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 must always be in effect.
In
circuit switching, each user typically gets a fixed share of the channel capacity. A
multiplexing scheme divides up the
capacity of the medium. Common multiplexing schemes include
time-division multiplexing and
frequency-division multiplexing. Channel access methods for circuit switching include
time-division multiple access,
frequency-division multiple access, 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,
token passing, etc.
References
Multiplexing
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