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Several ways of categorizing multiple-access schemes and protocols have been used in the literature. For example, Daniel Minoli (2009) [2] identifies five principal types of multiple-access schemes: FDMA, TDMA, CDMA, SDMA, and random access.
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". [1] [2] When they do transmit, nodes transmit their packet data in its entirety.
In the Ethernet protocol, when a communication collision happens (when two users of the medium try to send at the same time), each user waits for a random period of time before re-accessing the link. However, a user will wait ("back off") for a random amount of time proportional to the number of times it has successively tried to access the link.
ALOHA and the other random-access protocols have an inherent variability in their throughput and delay performance characteristics. For this reason, applications that need highly deterministic load behavior may use master/slave or token-passing schemes (such as Token Ring or ARCNET) instead of contention systems.
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. [1] The users transmit in rapid succession, one after the other, each using its own time slot.
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 spectrum.
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 the bandwidth of the channel into separate non-overlapping frequency sub-channels and allocating each sub-channel to a separate user.
Multiple Access with Collision Avoidance for Wireless (MACAW) [1] is a slotted medium access control (MAC) protocol widely used in ad hoc networks. [2] Furthermore, it is the foundation of many other MAC protocols used in wireless sensor networks (WSN). [2] The IEEE 802.11 RTS/CTS mechanism is adopted from this protocol.