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Information about Circuit Switching

Multiplex techniques
Circuit mode — for constant bandwidth
TDM | FDM | WDM | Polarization multiplexing | Spatial multiplexing (MIMO)
Statistical multiplexing — for variable bandwidth
Packet mode | Dynamic TDM | FHSS | DSSS | OFDMA
Related topics
Channel access methods | Media Access Control
In telecommunications, a circuit switching network is one that establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate. Each circuit that is dedicated cannot be used by other callers until the circuit is released and a new connection is set up. Even if no actual communication is taking place in a dedicated circuit then, that channel still remains unavailable to other users. Channels that are available for new calls to be set up are said to be idle.

The call

For call setup and control (and other administrative purposes), it is possible to use a separate dedicated signalling channel from the end node to the network. ISDN is one such service that uses a separate signalling channel while Plain Old Telephone Service (POTS) does not.

The method of establishing the connection and monitoring its progress and termination through the network may also utilize a separate control channel as in the case of links between telephone exchanges which use CCS7 to communicate the call setup and control information and use TDM to transport the actual circuit data.

Early telephone exchanges are a suitable example of circuit switching. The subscriber would ask the operator to connect to another subscriber, whether on the same exchange or via an inter-exchange link and another operator. In any case, the end result was a physical electrical connection between the two subscribers' telephones for the duration of the call. The copper wire used for the connection could not be used to carry other calls at the same time, even if the subscribers were in fact not talking and the line was silent.

Compared to packet

Since the first days of the telegraph it has been possible to multiplex multiple connections over the same physical conductor, but nonetheless each channel on the multiplexed link was either dedicated to one call at a time, or it was idle between calls. Circuit switching can be relatively inefficient because capacity is wasted on connections which are set up but are not in continuous use (however momentarily). On the other hand, the connection is immediately available and capacity is guaranteed until the call is disconnected.

Circuit switching contrasts with packet switching which splits traffic data (for instance, digital representation of sound, or computer data) into chunks, called packets, that are routed over a shared network. Packet switching networks do not require a circuit to be established and allow many pairs of nodes to communicate almost simultaneously over the same channel. Each packet is individually addressed precluding the need for a dedicated path to help the packet find its way to its destination.

Packet switching, in contrast, is the process of segmenting a message/data to be transmitted into several smaller packets. Each packet is labeled with its destination and the number of the packet. Each is dispatched and many may go via different routes. The original message is reassembled in the correct order at the destination.

As opposed to circuit switching, where a route is reserved from source to destination and the entire message is send in order so that the message does not have to be reassembled at the destination.

See also

External links

In electronics, telecommunications and computer networks, multiplexing (short muxing) is a term used to refer to a process where multiple analog message signals or digital data streams are combined into one signal. The aim is to share an expensive resource.
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Time-Division Multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but physically are taking turns on the channel.
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In fibre-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes multiple optical carrier signals on a single optical fibre by using different wavelengths (colours) of laser light to carry different signals.
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Statistical multiplexing is a type of communication link sharing. In statistical multiplexing, a communication channel is divided into an arbitrary number of variable bit-rate digital channels or data streams.
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Packet switching is a communications paradigm in which packets (discrete blocks of data) are routed between nodes over data links shared with other traffic. In each network node, packets are queued or buffered, resulting in variable delay.
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Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver.
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In telecommunications, direct-sequence spread spectrum (DSSS) is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that is being modulated.
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Orthogonal Frequency Division Multiple Access (OFDMA) is a multi-user version of the popular OFDM digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users as shown in the figure below.
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In telecommunications and computer networks, a channel access method or multiple access method allows several terminals connected to the same physical medium to transmit over it and to share its capacity.
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Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer OSI model (layer 2).
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Telecommunication is the transmission of signals over a distance for the purpose of communication. In modern times, this process typically involves the sending of electromagnetic waves by electronic transmitters, but in earlier times telecommunication may have involved the use of
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A telecommunication circuit is defined as follows:
  1. The complete path between two terminals over which one-way or two-way communications may be provided. See communications protocol.
  2. An electronic path between two or more points, capable of providing a number of channels.

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Channel, in communications (sometimes called communications channel), refers to the used to convey information from a sender (or transmitter) to a receiver.

Overview

A Channel can take many forms.
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A node is a device that is connected as part of a computer network. For example, a node may be a computer, personal digital assistant, cell phone, router, switch, or hub.
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terminal is a device which is capable of communicating over a line. Examples of terminals are telephones, fax machines, and network devices - printers, work stations, routers in a VoIP network.
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In telecommunications, a user is a person, organization, or other entity that employs the services provided by a telecommunication system, or by an information processing system, for transfer of information.
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In telecommunication, signalling (UK spelling) or signaling (US spelling) has the following meanings:
  • The use of signals for controlling communications.

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Separate channel signaling is a form of signaling in which the whole or a part of one or more channels in a multichannel system is used to provide for supervisory and control signals for the message traffic channels.
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SS7 protocol suite
Layer Protocols
Application INAP, MAP, IS-41...
TCAP, CAP, ISUP, ...
Transport SCCP
Network MTP Level 3
Data link MTP Level 2 ...
Physical MTP Level 1 ...
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Time-Division Multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but physically are taking turns on the channel.
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worldwide view of the subject.
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In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls.
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The electrical telegraph is a telegraph that uses electric signals. The electromagnetic telegraph is a device for transmission of written messages without physical transport of letters over wire.
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In electronics, telecommunications and computer networks, multiplexing (short muxing) is a term used to refer to a process where multiple analog message signals or digital data streams are combined into one signal. The aim is to share an expensive resource.
..... Click the link for more information.
Packet switching is a communications paradigm in which packets (discrete blocks of data) are routed between nodes over data links shared with other traffic. In each network node, packets are queued or buffered, resulting in variable delay.
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Packet switching is a communications paradigm in which packets (discrete blocks of data) are routed between nodes over data links shared with other traffic. In each network node, packets are queued or buffered, resulting in variable delay.
..... Click the link for more information.
Packet switching is a communications paradigm in which packets (discrete blocks of data) are routed between nodes over data links shared with other traffic. In each network node, packets are queued or buffered, resulting in variable delay.
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In telecommunications, message switching was the precursor of packet switching, where messages were routed in their entirety, one hop at a time. It was first introduced by Leonard Kleinrock in 1961.
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In computer science and telecommunications a call is:
  • Any attempt to set up a telecommunication circuit
  • A unit of traffic measurement
  • The actions performed by a call originator

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