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Digital Communication Question Paper - Dec 18 - Electronics And Telecomm (Semester 5) - Pune University (PU)
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Digital Communication - Dec 18
Electronics And Telecomm (Semester 5)
Total marks: 80
Total time: 3 Hours
INSTRUCTIONS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.
1.a.
Derive Mathematical expression for Signal to noise ratio in PCM system.
(8marks)
00
1.b.
Compare PCM and DM systems.
(6 marks)
00
1.c.
What is a strictly stationary process? Explain.
(6 marks)
00
2.a.
What is bit synchronization? Explain Early-late and early gate method?
(8 marks)
00
2.b.
A binary channel with 64 kbps bit rate is available for PCM Voice transmission find
(5 marks)
00
i) Number of quantization levels
ii) Number of bits per sample
iii) Sampling frequency , the voice signal is band limited to 3.4kHz
2.c.
What are the properties of line codes.
(4 marks)
00
3.a.
Explain Maximum likelihood ratio test. (LRT)
(4 marks)
00
3.b.
Derive the expression of SNR and probability of error for Matched filter in presence of AWGN noise channel.
(8 marks)
00
3.c.
Define Gaussian process state its properties.
(4 marks)
00
OR
4.a.
Explain geometrcal representation of signal and Gram-Schimitt Procedure.
(4 marks)
00
4.b.
Derive expression of SNR for Integrator and Dump circuit.
(8 marks)
00
4.c.
State the various properties of Match filters.
(4 marks)
00
5.a.
Find the probability of error for coherent FSK. when amplitude of I/P at coherent optimal reciever is 10mv and frequency 10 mHz, the signal corruptes with white noise of PSD $10^{-9}$ W/Hz , the data rate is 100 kbps. [erfc (1.01) = 0.1531, erfc(1.11) = 0.1164, erfc(1.22) = 0.0844, erfv(1.33) = 0.0599]
.
(8 marks)
00
5.b.
Explain QPSK generation with neat diagram and waveform.
(4 marks)
00
5.c.
Compare the performance of modulation schemes , BPSK , BFSK, QPSK, DPSK, M-ary PSK, M-ary FSK w.r.t.
(6 marks)
00
i) BW
ii) PSD
iii) probability of Error
iv) Application Bit rate
OR
6.a.
Derive the expression of Probability of error for BPSK receiver in presence of AWGN noise channel.
(8 marks)
00
6.b.
Explain coherent binary FSK signal generation
(4 marks)
00
6.c.
Explain M-ary PSK transmitter and receiver.
(6 marks)
00
7.a.
What is PN sequence ? Explain its properties with 4-stage Shift register
(6 marks)
00
7.b.
What are the advantages of FHSS.
(4 marks)
00
7.c.
Explain the concept of spread spectrum in advanced digital communication system
(6 marks)
00
OR
8.a.
Explain the concept of Processing gain, Probability of error and Concept of jamming.
(6 marks)
00
8.b.
Explain Fast and slow frequency hopping techniques.
(4 marks)
00
8.c.
Derive PSD for DSSS system and enlist its disadvantages.
(4 marks)
00
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