Channel access method

multiple accessmultiple access methodchannel accessmultiple access protocolChannel access methodsChannelsCodingmultiaccess channelmultiple-accessPower-division multiple access
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.wikipedia
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Multiplexing

multiplexedmultiplexmultiplexes
A channel access method is based on multiplexing, that allows several data streams or signals to share the same communication channel or transmission medium.
Carrier sense multiple access and multidrop communication methods are similar to time-division multiplexing in that multiple data streams are separated by time on the same medium, but because the signals have separate origins instead of being combined into a single signal, are best viewed as channel access methods, rather than a form of multiplexing.

Physical layer

physicalLayer 1PHY
In this context, multiplexing is provided by the physical layer.

Data link layer

Layer 2Data linkLayer-2
Media access control is a sub-layer in the data link layer of the OSI model and a component of the link layer of the TCP/IP model.

Multi-carrier code-division multiple access

multi-carrier code division multiple accessMC-CDMAmulti-carrier
Other techniques include orthogonal frequency-division multiple access (OFDMA) and multi-carrier code division multiple access (MC-CDMA).
Multi-carrier code-division multiple access (MC-CDMA) is a multiple access scheme used in OFDM-based telecommunication systems, allowing the system to support multiple users at the same time over same frequency band.

Space-division multiple access

SDMAspace division multiple accessSpace Division Multiple Access (SDMA)
Space-division multiple access (SDMA) transmits different information in different physical areas.
Space-division multiple access (SDMA) is a channel access method based on creating parallel spatial pipes (focused signal beams) using advanced antenna technology next to higher capacity pipes through spatial multiplexing and/or diversity, by which it is able to offer superior performance in radio multiple access communication systems (where multiple users may need to use the communication media simultaneously).

Medium access control

media access controlMACMAC layer
A channel access method is also based on a multiple access protocol and control mechanism, also known as medium access control (MAC).
When sending data to another device on the network, the MAC sublayer encapsulates higher-level frames into frames appropriate for the transmission medium (i.e. the MAC adds a syncword preamble and also padding if necessary), adds a frame check sequence to identify transmission errors, and then forwards the data to the physical layer as soon as the appropriate channel access method permits it.

Modulation

modulatedmodulatordigital modulation
Each message signal (each phone call) is modulated on a specific carrier frequency.
OFDM can be extended to multi-user channel access method in the orthogonal frequency-division multiple access (OFDMA) and multi-carrier code division multiple access (MC-CDMA) schemes, allowing several users to share the same physical medium by giving different sub-carriers or spreading codes to different users.

Multi-frequency time-division multiple access

multi-frequency time division multiple access
Multi-frequency time-division multiple access (MF-TDMA) combines time and frequency multiple access.

Carrier-sense multiple access with collision avoidance

CSMA/CAcarrier sense multiple access with collision avoidanceCollision avoidance (networking)
Common examples are CSMA/CD, used in Ethernet bus networks and hub networks, and CSMA/CA, used in wireless networks such as IEEE 802.11.
Carrier-sense multiple access with collision avoidance (CSMA/CA) in computer networking, is a network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by beginning transmission only after the channel is sensed to be "idle".

Token passing

token-passingtoken
On a local area network, token passing is a channel access method where a signal called a token is passed between nodes to authorize that node to communicate.

Communication channel

channelchannelscommunications channel
A channel access method is based on multiplexing, that allows several data streams or signals to share the same communication channel or transmission medium.

Token ring

IEEE 802.5TokenRingToken-Ring
This token passing is a channel access method providing fair access for all stations, and eliminating the collisions of contention-based access methods.

Reservation ALOHA

Reservation ALOHA, or R-ALOHA, is a channel access method for wireless (or other shared channel) transmission that allows uncoordinated users to share a common transmission resource.

Orthogonal frequency-division multiple access

OFDMAOrthogonal Frequency Division Multiple AccessOFDM
Other techniques include orthogonal frequency-division multiple access (OFDMA) and multi-carrier code division multiple access (MC-CDMA). An advanced form of FDMA is the orthogonal frequency-division multiple access (OFDMA) scheme, for example used in 4G cellular communication systems.
Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users.

Dynamic bandwidth allocation

Bandwidth-on-DemandDynamic Bandwidth
Due to its random character, it can be categorised as statistical multiplexing methods and capable of dynamic bandwidth allocation.

Frequency-hopping spread spectrum

frequency hoppingFHSSfrequency-hopping
Another form is frequency-hopping CDMA (FH-CDMA), based on frequency-hopping spread spectrum (FHSS), where the channel frequency is changed rapidly according to a sequence that constitutes the spreading code.
It is used as a multiple access method in the code division multiple access (CDMA) scheme frequency-hopping code division multiple access (FH-CDMA).

Frequency-division multiple access

FDMAfrequency division multiple accessFDD
The frequency-division multiple access (FDMA) channel-access scheme is based on the frequency-division multiplexing (FDM) scheme, which provides different frequency bands to different data streams.
Frequency division multiple access (FDMA) is a channel access method used in some multiple-access protocols.

Duplex (telecommunications)

half-duplexfull-duplexduplex
Examples of shared physical media are wireless networks, bus networks, ring networks and point-to-point links operating in half-duplex mode.
Where channel access methods are used in point-to-multipoint networks (such as cellular networks) for dividing forward and reverse communication channels on the same physical communications medium, they are known as duplexing methods.

Time-division multiple access

TDMAtime division multiple accessDynamic TDMA
The time-division multiple access (TDMA) channel access scheme is based on the time-division multiplexing (TDM) scheme.
Time-division multiple access (TDMA) is a channel access method for shared-medium networks.

Orthogonal frequency-division multiplexing

OFDMCOFDMOFDM system comparison table
OFDM in its primary form is considered as a digital modulation technique, and not a multi-user channel access method, since it is used for transferring one bit stream over one communication channel using one sequence of OFDM symbols.

Code-division multiple access

CDMAcode division multiple accessCDMA-450
The code division multiple access (CDMA) scheme is based on spread spectrum, meaning that a wider radio channel bandwidth is used than the data rate of individual bit streams requires, and several message signals are transferred simultaneously over the same carrier frequency, utilizing different spreading codes.
Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies.

Carrier-sense multiple access with collision avoidance and resolution using priorities

CSMA/CARPCSMA/CA
In computer networking, carrier-sense multiple access with collision avoidance and resolution using priorities (CSMA/CARP) is a channel access method.

Direct-sequence spread spectrum

DSSSDirect Sequence Spread SpectrumDS-CDMA
One form is direct-sequence CDMA (DS-CDMA), based on direct-sequence spread spectrum (DSSS), used for example in 3G cell phone systems.

General Packet Radio Service

GPRSGSM GPRS(E)GPRS
The multiple access methods used in GSM with GPRS are based on frequency division duplex (FDD) and TDMA.