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.