Midterm Exam I for CS 359T (Mobile Computing and Wireless Network)
Time: March 05 (Monday)
Required Materials
- Wireless Communications and Wireless Networks
- Mobile Networking
- C. Perkins,
"Mobile IP,"
IEEE Communications Magazine, Vol. 35, No. 5, (May 1997), pp. 84-99.
- P. Bhagwat, C. Perkins, S. Tripathi,
"Network layer mobility: an architecture and survey,"
IEEE Personal Communications, Vol. 3, No. 3, (June 1996), pp. 54-64.
- A. Snoeren and H. Balakrishnan,
"An End-to-End Approach to Host Mobility,"
Proceedings of ACM MobiCom 2000.
- Ad Hoc Networks
- E. Royer and C.-K. Toh,
"A review of current routing protocols for ad hoc mobile wireless networks,"
IEEE Personal Communications, Vol. 6, No. 2, (Apr. 1999), pp. 46-55.
- D. Johnson and D. Maltz,
"Dynamic Source Routing in Ad Hoc Wireless Networks",
Mobile Computing, edited by T. Imielinski and H. Korth,
Chapter 5, pages 153-181, Kluwer Academic Publishers, 1996.
- C. Perkins and E. Royer,
"Ad hoc On-Demand Distance Vector Routing,"
Proceedings of the 2nd IEEE Workshop on Mobile Computing Systems and App
lications, New Orleans, (Feb. 1999), pp. 90-100.
- TCP for Wireless Networks
- R. Caceres and L. Iftode,
"Improving the performance of reliable transport protocols in mobile computing environments,"
IEEE JSAC, Vol. 13, No. 5, (Jun 1995), pp. 850-857.
- H. Balakrishnan, V. Padmanabhan, S. Seshan, and R. Katz,
"A comparison of mechanisms for improving TCP performance over wireless links,"
IEEE/ACM Transactions on Networking, December 1997.
Format
- Close book, close papers.
- Interview type questions, simple answers (in a few sentences).
Sample Exam Questions
The exam will cover the basic knowledge and
what you need to know about mobile computing;
I won't give questions that test some obscure topics.
If you have read all the Required Papers and understood them,
you will be doing good in the exam and you don't need to prepare.
Here are some sample questions and some also include answers.
- If your signal strength is 100 and you are 1 meter from the basestation,
what is your signal strength when you are 2 meters from the basestation?
Answer: 25
- Describe "hidden terminal problem" and explain why Ethernet-type
collision detection algorithm won't work.
- What is horizontal handoff and what is vertical handoff?
Briefly explain their differences.
- What is "triangle routing" in Mobile-IP?
Answer: packets from MH to CH takes the shortest path,
but packets from CH to MH takes a longer, indirect path --
they must travel from CH to HA, and then from HA to MH.
- Define "handoff latency" in Mobile-IP.
List a few common approaches that may
reduce/elimilate such "handoff latency."
- Briefly explain the architectural difference between IETF Mobile-IP
and Columbia Mobile-IP.
- Among DSDV, DSR, AODV, and TORA, when topological changes make
a route invalid, which ones will notify the source?
Answer: DSR and AODV.
(Note: DSDV reconstructs the route table through periodic exchanges
of route information; TORA uses link reversal and route repair.)
- Explain why errors in a wireless network are bad for TCP performance.
Briefly explain how TCP snooping can improve this situation.
If it is a straightforward answer (like the first question),
you answer it in a straightforward way.
If the question requires explanation,
what I am looking for is an “elevator answer”.
Remember people always tell you that you should always be prepared to give
an “elevator talk” of your work,
so that you can explain to somebody during an elevator ride
from the conference floor to your hotel room floor
(which takes about 1 minute)?
You should do the same thing here.
If you are waiting on the elevator and run into a potential employer,
who happens to overhear the term “vertical handoff”
and wants to ask you about it,
you must be able to explain in 5 sentences -- what it is and why it matters --
to show that you know this field.
So in this exam, I am expecting the same --
please construct you answers precisely and concisely,
and use no more than 5 sentences.
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