BE Computer Engineering (Pokhara University) Data Communication (PU, CMM 220) Question Paper 2078
This is the official BE Computer Engineering (Pokhara University) Data Communication (PU, CMM 220) question paper for 2078, 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 2078 paper is a great way to practise under real exam conditions.
Section A: Long Answer Questions
Attempt all / any as specified.
(a) Differentiate between guided and unguided transmission media with suitable examples. Compare twisted-pair cable, coaxial cable and optical fiber on the basis of bandwidth, attenuation, cost and immunity to electromagnetic interference. (8 marks)
(b) A signal travels through a transmission medium and its power is reduced to one-half of its original value. Calculate the attenuation in decibels. If the same signal is then amplified by a factor of 10, find the overall gain in dB. (6 marks)
(a) With the help of neat waveform diagrams, explain Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK) and Phase Shift Keying (PSK). State one practical application of each. (8 marks)
(b) Draw the constellation diagram for QPSK and 8-PSK. A digital signal uses 8-PSK modulation. If the baud rate is 2000, what is the bit rate? (6 marks)
(a) Compare circuit switching, datagram packet switching and virtual-circuit packet switching with respect to setup delay, addressing overhead, resource reservation and suitability for bursty traffic. (8 marks)
(b) Explain, with a labelled diagram, the three phases of a circuit-switched connection. Why is circuit switching inefficient for data traffic? (4 marks)
(a) A bit stream 1101011011 is to be transmitted using the CRC generator polynomial (i.e. divisor 10011). Compute the CRC bits and show the complete codeword to be transmitted. Verify that the receiver detects no error. (8 marks)
(b) Explain how a single-bit error and a burst error are detected by CRC, and state the conditions a generator polynomial must satisfy to detect all single-bit errors. (4 marks)
Section B: Short Answer Questions
Attempt all / any as specified.
Differentiate between Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM) and Wavelength Division Multiplexing (WDM). Explain the difference between synchronous TDM and statistical TDM with a diagram.
State and explain the three main causes of transmission impairment: attenuation, distortion and noise. List the different types of noise that affect a communication channel.
State Nyquist's theorem and Shannon's capacity formula. A telephone channel has a bandwidth of 3000 Hz and an SNR of 30 dB. Calculate the maximum theoretical channel capacity using Shannon's formula.
Explain the steps involved in Pulse Code Modulation (PCM) with a block diagram. Define sampling, quantization and encoding, and state the sampling rate required for a signal band-limited to 4 kHz.
Compare the Stop-and-Wait ARQ, Go-Back-N ARQ and Selective-Repeat ARQ protocols on the basis of window size, number of retransmissions on error, and channel utilization.
Explain the concept of Hamming distance and its relation to error detection and correction capability. A code has a minimum Hamming distance of 5; how many errors can it detect and how many can it correct?
With the help of waveforms, explain the following line coding schemes: NRZ-L, NRZ-I, Manchester and Differential Manchester. State one advantage of Manchester encoding over NRZ.
Explain the framing and flow control functions of the data link layer. Describe byte stuffing and bit stuffing with an example for the flag pattern 01111110.