Solutions to Chapter 4 - Communication Networks

Communication Networks (2 nd Edition)
Chapter 4 Solutions
airport (“somewhere on the third level of parking lot A”). Sketch the sequence of events that
take place to set up this call. (Don’t concern yourself with the specifics of the conversation.)
Bob’s
Mobile
Station
Base
Station
L. A.
MSC
Phone
Switch
Telephone
Network
Visitor’s
location
register
Wife’s phone
c. In the meantime, Bob’s college roommate, Kelly, who now works in Hollywood calls Bob’s
cell phone. Note that Bob’s cell phone begins with the Chicago area code. Sketch the
sequence of events that take place to set up this call. Should this call be billed as local or long
distance
Kelly’s long-distance service provider sees Bob’s Chicago area code and proceeds with
connecting her to Bob’s Chicago cellular network. When the call arrives at Bob’s cellular network
(in the form of signaling traffic), Bob’s home MSC checks its home location register and sees that
Bob is in LA (recall that it found out about his whereabouts in part a)). The call is then forwarded
back to LA where the connection can be made via Bob’s temporary MSC and its visitors’ location
register.
Whether Bob or Kelley should be billed long distance depends on the setup of Bob’s “roaming
service”. If the three networks involved (two cellular and one wireline) are coordinated enough,
Kelly’s final connection could be routed directly from Hollywood to Bob’s mobile station directly.
In this case it could be possible to bill them both locally.
However, it is more likely that the connection will actually be made from Kelly to Bob’s home
network and then back to L. A. By dialing long distance, Kelly implicitly agrees that she will pay
the long distance charges for a call to Chicago. By using his phone in L. A. Bob expects to pay
long distance fees for all calls he receives (even local ones) because if someone from Chicago
calls him, the call must be carried by a long distance carrier. In this case, both Bob and Kelly will
pay long distance charges. She will pay the same as if she were dialing a regular Chicago
number (which she is), and Bob will pay as if he is receiving a call from a Chicago caller, say, his
wife.
70. Compare cellular wireless networks to the local loop and to the coaxial cable television system in
terms of their suitability as an integrated access network. In particular comment on the ability to
support telephone service, high-speed Internet access, and digital television service. Consider the
following two cases:
In question 45, the local loop and coaxial cable network were compared in terms of their ability to
act as integrated access networks. Here, we examine the ability of cellular wireless networks to
provide these services.
Each type of traffic on an integrated access network has very different characteristics. Digital
television requires high bandwidth and low loss. Although the signal can be compressed using
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