Carrier sense multiple access
- Carrier sense multiple access
Carrier Sense Multiple Access (CSMA) is a probabilistic Media Access Control (MAC) protocol in which a node verifies the absence of other traffic before transmitting on a shared physical medium, such as an electrical bus, or a band of electromagnetic spectrum.
"Carrier Sense" describes the fact that a transmitter listens for a carrier wave before trying to send. That is, it tries to detect the presence of an encoded signal from another station before attempting to transmit. If a carrier is sensed, the station waits for the transmission in progress to finish before initiating its own transmission.
"Multiple Access" describes the fact that multiple stations send and receive on the medium. Transmissions by one node are generally received by all other stations using the medium.
Types of CSMA
* 1-persistent CSMAWhen the sender (station) is ready to transmit data, it checks if the physical medium is busy. If so, it senses the medium continually until the it becomes idle, and then it transmits a piece of data (a frame). In case of a collision, the sender waits for a random period of time and attempts to transmit again.
* p-persistent CSMAThis protocol is a generalization of 1-persistent CSMA. When the sender is ready to send data, it checks continually if the medium is busy. If the medium becomes idle, the sender transmits a frame with a probability "p". In case the transmission did not happen (the probability of this event is "1-p") the sender waits until the next available time slot and transmits again with the same probability "p". This process repeats until the frame is sent or some other sender starts transmitting. In the latter case the sender waits a random period of time, checks the channel, and if it is idle, transmits with a probability "p", and so on.
* Nonpersistent CSMAWhen the sender is ready to send data, it checks if the medium is busy. If so, it waits for a random amount of time and checks again. When the medium becomes idle, the sender starts transmitting. If collision occurs, the sender waits for a random amount of time, and checks the medium, repeating the process.
ources
* Andrew S. Tanenbaum, "Computer Networks". Prentice Hall, Upper Saddle River, NJ (2003). 892 pp. ISBN 0-13-066102-3
ee also
*Carrier sense multiple access with collision detection
*Carrier sense multiple access with collision avoidance
*Local collision
*Remote collision
*jam signal
Wikimedia Foundation.
2010.
Look at other dictionaries:
Carrier Sense Multiple Access — (CSMA) вероятностный сетевой протокол канального (МАС) уровня. Узел, желающий передать пакет данных, выполняет процедуру оценки чистоты канала, то есть слушает шумы в передающей среде в течение заранее определённого периода времени. Если… … Википедия
Carrier Sense Multiple Access — Der englische Begriff Carrier Sense Multiple Access (CSMA) (deutsch etwa: Mehrfachzugriff mit Trägerprüfung) bezeichnet im Bereich der Telekommunikation und der Rechnernetze ein dezentrales, asynchrones Verfahren zum Erlangen des Zugriffsrechts… … Deutsch Wikipedia
Carrier sense multiple access — En telecomunicaciones, se entiende por Acceso Múltiple por Detección de Portadora (Carrier Sense Multiple Access) el escuchar el medio para saber si existe presencia de portadora en los momentos en los que se ocupa el canal. El fin es evitar… … Wikipedia Español
Carrier sense multiple access with collision detection — (CSMA/CD), in computer networking, is a network control protocol in which *a carrier sensing scheme is used. *a transmitting data station that detects another signal while transmitting a frame, stops transmitting that frame, transmits a jam… … Wikipedia
Carrier Sense Multiple Access/Collision Resolution — (CSMA/CR) ist ein Verfahren, das der Entdeckung und Vermeidung von Kollisionen auf geteilten Medien dient. Es kommt bei Feldbussen wie dem Controller Area Network (CAN) zum Einsatz. CSMA/CR ist dem nach IEEE 802.3 (Ethernet) standardisierten… … Deutsch Wikipedia
Carrier sense multiple access with collision avoidance — Saltar a navegación, búsqueda Contenido 1 Detalles 2 Usos 3 Problemas que resuelve CSMA/CA (con respecto a CSMA/CD) … Wikipedia Español
Carrier Sense Multiple Access / Collision Avoidance Point Coordination Function — ist ein Verfahren zur Vermeidung von Kollisionen in drahtlosen Netzwerken (Wireless LANs), bei dem der Access Point den Medienzugriff zentral steuert. Dazu richtet der Access Point neben der Wettbewerbsperiode (CP, Contention Period) eine… … Deutsch Wikipedia
Carrier Sense Multiple Access with Collision Detection — [engl.], CSMA/CD … Universal-Lexikon
Carrier sense multiple access with collision avoidance — In computer networking, CSMA/CA belongs to a class of protocols called multiple access methods. CSMA/CA stands for: Carrier Sense Multiple Access With Collision Avoidance.In CSMA, a station wishing to transmit has to first listen to the channel… … Wikipedia
Carrier Sense Multiple Access with Collision Avoidance — Pile de protocoles 7. Application 6. Présentation 5. Session 4. Tr … Wikipédia en Français
