CSMA with Binary Exponential Backoff / CD

Carrier sense multiple access (CSMA / CD）is a network protocol running at the medium access control (MAC) layer. It can sense or listen to whether the shared transmission channel is busy and delay transmission until the channel is idle.

When multiple stations send their frames simultaneously, a collision occurs. The backoff algorithm is a collision resolution mechanism commonly used to schedule retransmissions after Ethernet collisions. The waiting time a station waits before attempting to retransmit a frame is called the backoff time.

CSMA / CD algorithm

Steps1）When the frame is ready, the sending station will check if the channel is idle or busy.

Steps2）If the channel is busy, the station will wait until the channel becomes idle.

Steps3）If the channel is idle, the station will start sending and continue to monitor the channel to detect collisions.

Steps4）If a collision is detected, the work station will initiate the binary exponential compensation algorithm.

Steps5）the station will reset the retransmission counter and complete the frame transmission.

Binary exponential backoff algorithm in the case of collision

Steps1）the station will continue to transmit the current frame and the jam signal within the current time to ensure that all other stations detect the collision.

Steps2）the station will increase the retransmission counter c to indicate the number of collisions.

Steps3）the station will choose to transmit at 0 and2 ^c – 1range of random slot times. For example, in the first collision (i.e., c = 1）after that, the station will wait for 0 or1slot time. After the second collision (i.e., c = 2），the station will wait for 0 to3slots between any two slots. After the third collision (i.e., c = 3），the station will wait for 0 to7Any time between slots, and so on.

Steps4）If the radio station selects a number