The random variable R (Figure 12.13) is designed to give stations different delays when a collision has occurred. To alleviate the collision, we expect that different stations generate different values of R. To show the point, find the probability that the value of R is the same for two stations after

Figure 12.13

a. The first collision.

b. The second collision.

Station has a frame to send K = 0 Legend T: Frame average transmission time K : Number of attempts R : (random number): 0 to 2* 1 Tp: (Backoff time) = R Tf Wait TB Apply one of the persistence methods seconds Create random Done or [false] Transmit number R collision? and receive [true] [true] Send a Collision K < 15 ? [true] K = K + 1 |[false] jamming signal detected? [false] Abort Success