CS 898T Mobile and Wireless Networks - Homework 2 - Name:_________________

    Assigned: Monday, February 23 
    Due: Wednesday, March 3 (in class)

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

    (50 points - 10 points for each question) 

    1. What is direct sequence spread spectrum? 
       List its advantages and disadvantages. 
       What is frequency hopping spread spectrum?
       List its advantages and disadvantages. 
       Give an example system which uses DSSS or FHSS respectively.


    2. What is the cellular system for mobile communications? 
       List its advantages and disadvantages. 
       Describe two types of the frequency assignment.


    3. Describe the problems when CSMA/CD is applied to wireless networks.
       Describe how MACA solve the above problems.


    4. What is a good code for CDMA? 
       Redo the CDMA example of section 3.5, but now add random 'noise'
       to the transmitted signal (-2, 0, 0, -2, +2, 0). Add, for example,
       (1, -1, 0, 1, 0, -1). In this case, what can the receiver detect
       for sender A and B repectively? Now include the near/far problem.
       How does this complicate the situation? What would be possible
       countermeasures?


    5. Name the main elements of the GSM system architecture and describe
       their functions. What are the advantages of specifying not only the
       radio interface but also all internal interfaces of the GSM system?