Question

R15. Suppose users share a 2Mbps link. Also suppose each user transmits continuously at 1Mbps when transmitting, but each user transmits only 20 percent of thetime.
a. When circuit switching is used, how many users can be supported?
b. For the remainder of this problem, suppose packet switching is used. Why there be essentially no queuing delay before the link if two or fewer users transmit at thesame time? Why will there be a queuing delay if three users transmit at the same time?
c. Find the probability that a given user is transmitting.
d. Suppose now there are three users. Find the probability that at any given time, all three users are transmitting simultaneously.

Answer 1

Dear User,

a) Given,Total transmission rate = 2MbpsMinimum transmission rate required by each user = 1MbpsTherefore, the number of userssupported
b) Given that each user transmits continuously at 1Mbps when transmitting. Suppose packet switching is used, if two or fewer users transmit at the sametime, a maximum of 2Mbps will be required. Also given that users share a 2Mbps link. So there will be no queuing delay before the link.
While three users transmit at the same time, a maximum of 3Mbps will be required which is more than the given shared link(2Mbps). So, there will bequeuing delay before the link.

c)
Each user transmits only 20 percent of the time.So, the probability that a given user is transmitting
d)Given,Total number ofusers=3Number of users transmitting = 3Since, each user transmits 20 percent of the time.Hence, probability, By using binomial distribution,the probability of3 users transmitting simultaneously,



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