Channel access method

multiple accesschannel accessmultiple access methodChannelsmultiple access protocolCodingmultiaccess channelmultiple-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

physicalPHYlayer 1
In this context, multiplexing is provided by the physical layer.
Carrier sense and collision detection utilized by some level 2 multiple access protocols

Data link layer

layer 2Data linkdatalink layer
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.
Multiple access protocols for channel-access control, for example CSMA/CD protocols for collision detection and re-transmission in Ethernet bus networks and hub networks, or the CSMA/CA protocol for collision avoidance in wireless networks.

Medium access control

media access controlMACEMAC
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 block 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. Controlling when data is sent and when to wait is necessary to avoid congestion and collisions, especially for topologies with a collision domain (bus, ring, mesh, point-to-multipoint topologies).

Multi-carrier code-division multiple access

MC-CDMAmulti-carrier code division multiple accessmulti-carrier
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.

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.

Direct-sequence spread spectrum

Direct Sequence Spread SpectrumDSSSdirect sequence
One form is direct sequence spread spectrum (DS-CDMA), used for example in 3G cell phone systems.
Some practical and effective uses of DSSS include the Code Division Multiple Access (CDMA) channel access method and the IEEE 802.11b specification used in Wi-Fi networks.

Carrier-sense multiple access with collision avoidance

CSMA/CAcarrier sense multiple access with collision avoidancecollision avoidance
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".

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.
Multiple access channel: In this channel, multiple senders transmit multiple possible different messages over a shared physical medium to one or several destination nodes. This requires a channel access scheme, including a media access control (MAC) protocol combined with a multiplexing scheme. This channel model has applications in the uplink of the cellular networks.

Token passing

token-passingtoken
Token passing:
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.

Carrier sense multiple access with collision avoidance and resolution using priorities

CSMA/CA
[[Carrier sense multiple access with collision avoidance and Resolution using Priorities]] (CSMA/CARP)
In computer networking, carrier sense multiple access with collision avoidance and resolution using priorities (CSMA/CARP) is a channel access method.

Wavelength-division multiple access

Wavelength division multiple access (WDMA)
Wavelength-division multiple access (WDMA) is a channel access method based on wavelength-division multiplexing.

Token ring

IEEE 802.5TokenRing802.5
Token ring
This token passing is a channel access method providing fair access for all stations, and eliminating the collisions of contention-based access methods.

Contention (telecommunications)

contentioncontention systemsnetwork
Contention based random multiple access methods
A contention based channel access (multiple access) protocol is a protocol where data packet collisions may occur.

Dynamic bandwidth allocation

Dynamic Bandwidth
Due to its random character, it can be categorised as statistical multiplexing methods and capable of dynamic bandwidth allocation.
Channel access method

Reservation ALOHA

Reservation ALOHA (R-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

OFDMAOFDMorthogonal frequency division multiple access
An advanced form of FDMA is the orthogonal frequency-division multiple access (OFDMA) scheme, for example used in 4G cellular communication systems. Orthogonal frequency-division multiple access (OFDMA), based on Orthogonal frequency-division multiplexing (OFDM)
Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users.

Frequency-division multiple access

FDMAfrequency division multiple accessAnalog
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 multiple-access protocol.

Frequency-hopping spread spectrum

frequency hoppingFHSSfrequency-hopping
Another form is frequency-hopping (FH-CDMA), 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).

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. GSM with the GPRS packet switched service combines FDD and FDMA with slotted Aloha for reservation inquiries, and a Dynamic TDMA scheme for transferring the actual data.
Time-division multiple access (TDMA) is a channel access method for shared-medium networks.

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.

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.

Orthogonal frequency-division multiplexing

OFDMorthogonal frequency division multiplexingCOFDM
Orthogonal frequency-division multiple access (OFDMA), based on Orthogonal frequency-division multiplexing (OFDM)
The OFDM-based multiple access technology OFDMA is also used in several 4G and pre-4G cellular networks, mobile broadband standards and the next generation WLAN:

General Packet Radio Service

GPRSGSM GPRS(E)GPRS
GSM with the GPRS packet switched service combines FDD and FDMA with slotted Aloha for reservation inquiries, and a Dynamic TDMA scheme for transferring the actual data.
The multiple access methods used in GSM with GPRS are based on frequency division duplex (FDD) and TDMA.

Radio resource management

radio-resource managementRadio Resourceradio resources
Radio resource management for inter-base station interference control
Dynamic bandwidth allocation using resource reservation multiple access schemes or statistical multiplexing, for example Spread spectrum and/or packet radio