Pokhara University
Bachelor of Engineering in Computer Engineering
Semester 3 · PU Spring
Course Title: Data Communication
Full Marks: 100Pass Marks: 45Time: 3hrs.
Candidates are required to give their answers in their own words as far as practicable.
- 2.15
- a) Define continuous and discrete time signals. Illustrate graphically unit step signal, ramp signal, impulse signal, sinusoidal signal and signum signal with their mathematical relation.
- b) Define LTI system. Check the linearity and time invariance of the following system. y(n) = nx(n)
- 3.15
- a) Explain layers of the OSI model.
- b) Define electromagnetic spectrum for telecommunication. Briefly explain ground wave, sky wave and line of sight (LOS) propagation.
- 4.15
- a) Briefly explain attenuation, distortion and noise that occurs in data communication. Why are they called transmission impairments? ae) If the frame is x” + x5 + 1 by the generator polynomial x3 +1, what would be the transmitted frame using CRC?
OR
Encode the given five source symbols (messages) using Huffman codes and find its efficiency . PProbabiliy [04 [02 [o2fo1 for}
- 5.22
- a) When is the Retransmission necessary? Explain about stop and wait ARQ protocol for the damaged frame.
- b) Briefly explain circuit switching and packet switching. —_—-» t
- b) What is multilevel modulation? Briefly explain with a suitable example. —
- a) ATMand Frame Relay ——— b)TCPAP layer ©) Very Small Aperture Terminal (VSAT) é
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