BE Computer Engineering (Pokhara University) Data Communication (PU, CMM 220) Question Paper 2079
This is the official BE Computer Engineering (Pokhara University) Data Communication (PU, CMM 220) question paper for 2079, as set in the regular annual examination. It carries 100 full marks and a time allowance of 180 minutes, across 12 questions. On Kekkei you can attempt this Data Communication (PU, CMM 220) past paper online with a timer, get instant AI feedback and step-by-step solutions, and track the topics where you lose marks — completely free. Whether you are revising for your BE Computer Engineering (Pokhara University) Data Communication (PU, CMM 220) exam or solving previous years' question papers, this 2079 paper is a great way to practise under real exam conditions.
Section A: Long Answer Questions
Attempt all / any as specified.
(a) Distinguish between analog and digital signals, and explain the relationship between bit rate, baud rate, and bandwidth with the help of suitable examples. (8)
(b) Compare guided and unguided transmission media. With neat diagrams, explain the construction and operating characteristics of optical fiber cable, and state two advantages it has over coaxial cable. (7)
(a) Explain the process of Pulse Code Modulation (PCM) with a block diagram, clearly describing the sampling, quantization, and encoding stages. State the Nyquist sampling theorem. (9)
(b) A signal band-limited to 4 kHz is sampled and each sample is encoded using 8 bits. Calculate the minimum sampling rate and the resulting bit rate of the PCM output. (6)
(a) Compare circuit switching, datagram packet switching, and virtual-circuit packet switching in terms of connection setup, addressing overhead, delay, and resource utilization. (9)
(b) Explain the working of the Stop-and-Wait ARQ protocol with a timing diagram, and describe how it handles a lost data frame and a lost acknowledgment. (6)
(a) Explain how the Cyclic Redundancy Check (CRC) detects errors. For the data word 1101011011 and the generator polynomial G(x) = x^4 + x + 1, compute the CRC and show the transmitted code word using binary division. (10)
(b) State the relationship between Hamming distance and a code's ability to detect and correct errors. How many bit errors can a code with a minimum Hamming distance of 5 detect and correct? (5)
Section B: Short Answer Questions
Attempt all / any as specified.
Differentiate between Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM). With a neat diagram, explain how synchronous TDM works and why guard bands are required in FDM.
Explain the three main causes of transmission impairment: attenuation, distortion, and noise. A signal travels through a transmission medium and its power is reduced to one-half. Express this attenuation in decibels (dB).
With the help of waveforms, explain the three basic digital-to-analog modulation techniques: Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), and Phase Shift Keying (PSK). Why is QPSK preferred over BPSK?
Explain the sliding window concept used in flow control. Differentiate between Go-Back-N ARQ and Selective Repeat ARQ in terms of window size, buffering, and retransmission behavior.
With appropriate signal diagrams, explain the following line-coding schemes: (a) NRZ-L, (b) NRZ-I, (c) Manchester, and (d) Differential Manchester. State one advantage of self-synchronizing schemes.
State and explain the Shannon capacity formula and the Nyquist bit-rate formula. A telephone channel has a bandwidth of 3000 Hz and an SNR of 3162 (35 dB). Calculate the maximum theoretical channel capacity using Shannon's formula.
Explain the principle of error detection using a simple parity check and a two-dimensional parity check. Show with an example how a two-dimensional parity check can both detect and correct a single-bit error.
Write short notes on any TWO of the following: (a) Spread spectrum techniques (FHSS and DSSS) (b) Wavelength Division Multiplexing (WDM) (c) Unguided media: radio, microwave, and infrared waves