Wireless Security

CS547 Wireless Networking and Security
Exam 2
Question 1 (10 pts):
Prove that, if every user code is orthogonal to every other user code in CDMA, unwanted signals
can easily be filtered out. Note: you have to show me a generalize proof. Showing me examples of
three or more instances or examples is NOT a proof!
Question 2 (10 pts):
A message needs to be fragmented into 12 frames with each frame having a probability of 92%
of arriving error free. Calculate the probability of the entire message getting through.
Question 3 (10 pts):
Using the Hamming algorithm, determine whether the received 24-bit Hamming code 0x616FB3
is error-free. If it is not error-free and assuming that there is no error masking, fix the error.
Note: read the binary values from left to right, i.e. the leftmost bit is bit # 1.
Question 4 (10 pts):
Using CRC, calculate the transmitted data for a message M = 1011011101001010 and a dividing
polynomial P = x5 + x3 + x2 + 1.
Question 5 (15 pts):
Briefly describe five ways of increasing the capacity of cellular systems.
Question 6 (5 pts):
Explain why a 2-cell or a 5-cell reuse pattern does not exist in symmetrical cellular arrangements.
Question 7 (10 pts):
In satellite communications that follows the free space law, which option will provide more
received power: doubling the effective area of both antennas or doubling the transmission
frequency? Justify your answer.
Question 8 (10 pts):
Choose between FHSS and DSSS and justify your choice with a convincing argument!.
Question 9 (20 points):
Write a two-page research report on “Jamming Satellite Communications.”
For research problems, you are expected to provide a reference section and properly cite your
sources.