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Data Communication. Question Paper
Data Communication.
Course:Diploma In Information Technology
Institution: Mombasa Polytechnic University College question papers
Exam Year:2010
THE MOMBASA POLYTECHNIC UNIVERSITY COLLEGE
Faculty of Engineering & Technology
DEPARTMENT OF COMPUTER SCIENCE & INFORMATION TECHNOLOGY
DIPLOMA IN INFORMATIOM TECHNOLOGY (DIT)
END OF SEMESTER EAMINATION
APRIL / MAY 2010 SERIES
DATA COMMUNICATION
TIME: 2 HOURS
INSTRUCTIONS TO CANDIDATES
- THERE ARE FIVE QUESTIONS IN THIS PAPER.
- SECTION A IS COMPULSORY.
- ANSWER ANY TWO QUESTIONS IN SECTION B.
(C) 2010 Department of Computer Science
SECTION A
QUESTION 1
(a) State the OSI layers where segments, bits, frames and packets are handled (2 Marks)
(b) Identify any THREE levels of synchronization that are applicable in data communication (3 Marks)
(c) Outline THREE elements of Data communication system (3 Marks)
(d) Outline FOUR forms of information that can be transmitted using a data communication channel (4 Marks)
(e) Classify the following transmission media as either guided or unguided
(i) Infrared
(ii) Coaxial cable
(iii) Multimode graded – index fibre
(iv) Laser (4 Marks)
(f) With the aid of a diagram describe the following
(i) Half duplex
(ii) Full duplex (4 Marks)
(g) (i) Define parallel data transmission as applied in data communication
(ii)Explain TWO limitations of parallel data transmission (5 Marks)
(h) State any TWO meaning of the term modulation as applied in data communication
(ii)State any TWO advantages of Delta Modulation DM over Pulse Code Modulation PCM
(iii)State any limitation of DM (5 Marks)
SECTION B
QUESTION 2
(a) Given data as 010011, sketch the encoded signals on the same plane of the following encoding schemes are used
- Manchester
- Differential manchester
- Non- Return to Zero Invented (NRZI) (6 Marks)
(b) Outline any TWO weaknesses of bi-polar encoding schemes (2 Marks)
(c) Describe the following modulation schemes with the aid of a diagram
(I) Frequency Shift Keying FSK
(II) Frequency Modulation FM (4 Marks)
(d) Distinguish between Amplitude Modulation AM and amplitude Shift Keying ASK, with the aid of a sketch (4 Marks)
(e) Determine the upper and lower side band of an amplitude Modulated signal given that the modulating signal range is 100-3400 Hzs and the carrier frequency is 60 KHzs (4 Marks)
QUESTION 3
(a) (i) Distinguish between Forward Error Correction (FEC) and Backward Error Correction (BEC).
(ii)Distinguish between longitudinal redundacy check and cyclic redundancy check as used in data communication (6 Marks)
(b) Calculate the CRC needed for the transmission of data stream 1001011 (4 Marks)
(c) Describe the following transmission line impairments.
(i) Delay distortion
(ii) Attenuation
(iii) Jitter
(iv) White noise (8 Marks)
(d) Scramble the following data bit stream 1000 0001 1000 0000 0011 using
(i) B8ZS (2 Marks)
QUESTION 4
(a) Outline any THREE ways in which a transmission medium can contribute to signal errors during transmission. (6 Marks)
(b) Distinguish between the transmission of light through Multi mode fibre and single mode fibre with the aid of a diagram. (4 Marks)
(c) State FOUR advantages and TWO disadvantages of optical fibres (6Marks)
(d) State any FOUR desirable characteristics of optical detectors (4 Marks)
QUESTION 5
(a) Compare optical fibre and microwave link in terms of
• Transmission speed
• Security of data
• Bandwidth
• Electromagnetic interference (4 Marks)
(b) Distinguish between DCE and DTE as applied in data communication with the aid of a diagram (4 Marks)
(c) Determine the channel capacity given a frequency range of 100 Hzs to 3400 Hertzs, if a 16 level MODEM is used (5 Marks)
(d) (i) describe asynchronous transmission with the aid of a sketch
(ii) Outline TWO advantages of asynchronous transmission
(iii) Outline TWO disadvantages of asynchronous transmission (7Marks)
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