HW 1
1. (이 문제는 interactive exercise 의 문제와 유사합니다. 거기에 예제도 있으니
참고하십시오.)
This question requires a little bit of background in probability (but we'll try to help
you though it in the solutions). Consider the two scenarios below:
•
A circuit-switching scenario in which Ncs users, each requiring a bandwidth
of 10 Mbps, must share a link of capacity 150 Mbps.
•
A packet-switching scenario with Nps users sharing a 150 Mbps link,
where each user again requires 10 Mbps when transmitting, but only
needs to transmit 20 percent of the time.
Answer the following questions:
a.
When circuit switching is used, what is the maximum number of circuit-
switched users that can be supported? Explain your answer.
b.
What is the probability that one user (any one among the Nps users) is
transmitting, and
the remaining users are not transmitting? When one user is transmitting,
what fraction of the link capacity will be used by this user?
c.
What is the probability that any 15 users (of the total Nps users) are
transmitting and the remaining users are not transmitting?
d.
Assume that packet switching is said to support N users if the probability
that more than 15 users are active is less than 0.004. How many users is the
packet switching able to support?
