CS 898T Mobile and Wireless Networks - Homework 4 - Name:_________________

    Assigned: Thursday, July 14 
    Due: Thursday, July 21 (in class)

    Please show all work on a separate sheet attached to this sheet.
    For each question write key points. 


    1. (2 points) What is a wireless mesh network?
       (3 points) List three advantages of hybrid wirelss networks.

    2. 1) (4 points) Briefly classify MAC protocols for ad hoc wireless 
          networks. 
       2) (4 points) Briefly explain the idea behind each type of protocols.
       3) (3 points) List three advantages of using directional antennas.

    3. (8 points) Briefly mention at least four reasons why TCP does not 
       perform well in ad hoc wireless networks? 

    4. (6 points) Encrypt the plaintext "enjoyyoursummerbreak" using a 
       transposition cipher based on the key "TIGER".

    5. Using the RSA public key cryptography algorithm.

     1) (3 points) If p = 17 and q = 19, list 3 legal values for d.
     2) (3 points) If p = 7, q = 11, and d = 13, find e.
     3) (4 points) Using p = 7, q = 17, and d = 19, find e. 
        (3 points) Encrypt "cheers" where a = 1, b = 2, c = 3, ...., 
        and z = 26.

    6. 1) (3 points) What is Wired Equivalent Privacy (WEP)? 
       2) (3 points) Name at least two problems of WEP.
       3) (4 points) Briefly describe how 802.11i enhance security in 
          wireless LANs.