The CSMA (Carrier Sense Multiple Access) does not define the procedure for a collision. That is the reason CSMA was never implemented.
CSMA/CD (Carrier Sense Multiple Access with collision detection) adds a procedure to handle a collision. In this procedure, any station can send a frame. The station then monitors the medium to see if transmission was successful. If so, the station is finished. If, however, there was a collision the frame need to be sent again. To reduce the probability of collision, the second time, the station waits, it needs to back off.
While the CSMA/CA procedure differs from the CSMA/CD procedures in that there is no collision. This procedure is helpful in avoiding collision. The station uses one of the persistence strategies. After it finds the line idle, the station waits an IFG (Inter-frame Gap) amount of time. It then waits for another random amount of time. After that, it sends frame and sets a timer. The station waits for an acknowledgement from the receiver. If it receives the acknowledgment before the timer expires, the transmission is successful. If the station does not receive an acknowledgement; it knows that something is wrong (either the frame is lost or an acknowledgement is lost). The station increments the value of the back off parameter, waits for a back off amount of time, and re-senses the line. CSMA/CA is used in wireless LANs.
CSMA/CD (Carrier Sense Multiple Access with collision detection) adds a procedure to handle a collision. In this procedure, any station can send a frame. The station then monitors the medium to see if transmission was successful. If so, the station is finished. If, however, there was a collision the frame need to be sent again. To reduce the probability of collision, the second time, the station waits, it needs to back off.
While the CSMA/CA procedure differs from the CSMA/CD procedures in that there is no collision. This procedure is helpful in avoiding collision. The station uses one of the persistence strategies. After it finds the line idle, the station waits an IFG (Inter-frame Gap) amount of time. It then waits for another random amount of time. After that, it sends frame and sets a timer. The station waits for an acknowledgement from the receiver. If it receives the acknowledgment before the timer expires, the transmission is successful. If the station does not receive an acknowledgement; it knows that something is wrong (either the frame is lost or an acknowledgement is lost). The station increments the value of the back off parameter, waits for a back off amount of time, and re-senses the line. CSMA/CA is used in wireless LANs.
