Multiple access protocols
There are two types of links: point-to-point and broadcast (shared wire or medium). In single shared broadcast channel two or more simultaneous transmissions may collide. We need a multiple access protocol that determines how nodes share channel. An ideal multiple access protocol satisfies the following desiderata given a broadcast channel of R bps:
- When one node wants to transmit, it can send at rate R.
- When M nodes want to transmit, each can send at average rate R/M
- Fully decentralized:
- No special node to coordinate transmissions
- No synchronization of clocks, slots
- Simple
There are three broad classes of MAC (Medium Access Control) protocols:
- Channel partitioning: divide channel into smaller “pieces”, e.g. Frequency Division Multiplexing, Time Division Multiplexing
- Random access: MAC protocol specifices how to detect collisions and how to recover, e.g. ALOHA, slotted ALOHA, CSMA/CA
- Taking turns
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Project
Contact
This resource was developed as part of an Erasmus+ project, funded with support from the European Commission under grant agreement 2016-1-SE01-KA203-22064.
The project was a collaboration between:
- The University of Borås, Sweden
- The University of the Highlands and Islands, Scotland
- The University of Alcalá, Spain
- Digital Connections, Scotland
This resource has been released under Creative Commons license CC-BY-SA 4.0.
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- Technical resource development – The University of the Highlands and Islands Educational Development Unit - EDU (edu@uhi.ac.uk)
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