CMPE581 Exam Questions from Previous Years

EASTERN MEDITERRANEAN UNIVERSITY

CMPE-581 Modeling Multimedia Systems

Final Exam

Duration: 120 minutes.            Open book, Open notes.                  February 9,  2001

Q1) (20 points)

Discuss the difficulties involved in multimedia presentations :

1. In multicast mode,    
2. In broadcast mode,   
   
   compared to a unicast (node-to-node) presentation. Assume connection speeds may be different for different destinations.

Q2) (25 points)

1. Explain the following types of redundancy in multimedia data :
   (i) Spatial     (ii) Temporal           (iii) in Scale
   
2. Why do we use lossy compression techniques although there are known lossless compression methods? Explain.
   
   
3. Draw the Huffman code tree for characters (a, b, c, d, e, f), given their occurrence probabilities as follows :  p(a)=1/16,  p(b)=4/8,  p(c)=1/8,  p(d)=1/32,  p(e) = 2/8,  p(f)=1/32

Q3) (30 points.)

1. What are the advantages of 'layered' multimedia synchronization models?
2. Compare the layered models of (Blakowski&Steinmetz) and (Aktun&Aybay), emphasizing their differences.

Q4) (25 points.)  

1. Define multimedia terms 'lip synchronization' and 'skew'.
2. Discuss experimental findings on skew tolerance in lip synchronization.
3. How can one correct/reduce lip synchronization problems :
   
   (i) in live broadcasting       (ii) in video-on-demand applications?

EASTERN MEDITERRANEAN UNIVERSITY

CMPE-581 Modeling Multimedia Systems

Final Exam

Duration: 120 minutes.            Open book, Open notes.                     February 9, 2002

Q1) (30 points)  Assume there is a 30 second video movie that is formed of 1024 x 768 pixel 'frames'. Each pixel is represented by 8 bits of color information. For each second of the movie, 24 consecutive still 'frames' are used.

1. Compute the amount of information that has got to be transferred (in bits) for this movie, if it is to be sent to a remote destination over a communication network.
2. Find out how much time it will take to send this movie over :

1. an ISDN line (128 kbps),
2. a 1 Mbps satellite link,
3. a 34 Mbps Internet2 link.

Q2) (15 points) Assume we have an alphabet of six characters : (a, b, c, d, e, f).

Construct the Huffman code tree for these characters, and decide on their optimal binary Huffman codes, given their occurrence probabilities as follows : 

p(a)=0.1,  p(b)=0.05,  p(c)=0.15,  p(d)=0.3,  p(e) = 0.35,  p(f)=0.05

Q3) (30 points.)  Consider the following communication networking technologies :

i) Ethernet   ii) Token Ring   iii) X.25   iv) ATM

1. Which of these technologies permit broadcasting? Which of them permit multicasting? Explain.
2. Which of these technologies are suitable for real-time distributed multimedia systems? Explain.

Q4) (25 points.)  Consider an audio/video stream that must be played synchronously. For such a stream, what are the advantages and disadvantages of :

1. Synchronization at the source,
2. Synchronization at the destination?
   

EASTERN MEDITERRANEAN UNIVERSITY

CMPE-581 Modeling Multimedia Systems

Final Exam

Duration: 120 minutes.                 Open book, Open notes.                  June 15, 2009

Q1) (20 points) Explain the following terms giving examples and drawing illustrative diagrams:

a)    Reuse factor (in wireless networks)

b)   Jitter

Q2) (20 points) Discuss the difficulties involved in "multicasting" multimedia data to a number of clients from a single server in detail and compare this technique with the peer-to-peer (server-to-one client) case.

Q3) (20 points) In distributed multimedia presentations, there are two main approaches with respect to where the synchronization operations take place: synchronization at the source, and synchronization at the destination.

1. Explain these approaches using diagrams,
2. Comment on the conditions under which synchronization at the source is preferable.

Q4) (20 points) List and explain the types of frames in MPEG coding of video frames.

Q5) (20 points) Discuss the basic properties of the Time Division Multiple Access (TDMA) technique. How does it differ from the Frequency Hopping (FH) technique? What are the advantages (if any) of TDMA over FH?

EASTERN MEDITERRANEAN UNIVERSITY

CMPE-581 Modeling Multimedia Systems

Final Exam

Duration: 100 minutes.                   Open book, Open notes.                   June 8, 2010

Q1) (20 points) Explain the following terms giving examples and drawing illustrative diagrams:

a)    Huffman coding

b)   Nyquist's Sampling Theorem

Q2) (20 points)  Explain what quantization is, and discuss its importance in picture quality for image transmission with an example.

Q3) (30 points) Consider your work for Assignment#2.

1. What are the current problems in video-on-demand networks?
2. What kind of new developments in terms of hardware and/or software do you expect in the future, concerning video-on-demand applications?

Q4) (30 points) According to a news article published at industry.bnet.com, the GSM standard, which is the most widely used cellular technology in the world, has recently been the target of some successful security hazing.  A German researcher announced that he deciphered and published the GSM encryption algorithm. Then, researchers at the Weizmann Institute of Science cracked a security algorithm for 3G networks in less than two hours. In April 2010, it was shown that it is possible to track a GSM user's location and listen to voicemail and calls. Cellular security vendor Cellcrypt has already demonstrated a mobile fake base station for intercepting GSM calls.

1. Considering all these, discuss why these security problems are observed in GSM networks.
2. What would you recommend to ensure the safety of mobile communications?