 Digital Communication -Engineering-Nov2019 - Grad Plus

# Digital Communication -Engineering-Nov2019

T.E. (E & TC)
DIGITAL COMMUNICATION
(2015 Pattern) (Semester – I)

Time : 2½ Hour
Max. Marks : 70
Instructions to the candidates:
1) Answer Q.1 or Q.2, Q.3 or Q.4, Q.5 or Q.6, Q.7 or Q.8.
2) Assume suitable data if necessary.
3) Figures to the right side indicate full marks.

Q.1 a) What is narrowband noise? Show the generation of narrowband noise from its in phase and quadrature components. [6M]
b) A binary channel with 32kbps bit rate is available for PCM voice transmission. Find [6M]
i) No. of quantization levels
ii) No. of bits per sample
iii) sampling frequency
The voice signal is band limited to3.4KHz.

c) What is bit synchronization? Explain Early-Late bit synchronizer in detail.[8M]

OR

Q2) a) List properties of Line Codes (Data Formats). Draw the following line codes for bit stream 10110010 [8M]
i) Polar RZ
ii) Polar NRZ
iii) Manchester
iv) AMI
v) Polar Quaternary
vi) Unipolar RZ

b) What is White noise? Explain. [6M]

c) With the help of neat block diagram, explain Pulse Code Modulation.[6M]

Q3) a) Explain likelihood function. [6M]

b) Derive an expression for probability of error of matched filter. [8M]

c) State properties of Match filter. [2M]

OR

Q4) a) Derive an expression for signal to noise ratio of integrator and dump filter. [6M]

b) Find impulse response of matched filter whose input is given by [6M]
g(t) = A sin(2πt/T) ; 0 < t < T
= 0; Otherwise

c) Draw block diagram and explain in detail correlation receiver. [4M]

Q5) a) Draw block diagram of BPSK and explain it. [4M]

b) With the help of block diagram and waveforms, explain generation of coherent BFSK. [6M]
Binary data is transmitted using PSK at a rate 5Mbps over RF link having bandwidth 10 MHz. Find signal power required at receiver input so that error probability is less than or equal to 10–4 watt/Hz. Q(3.71) = 10–4, No/2 = 10–10. [6M]

OR

Q6) a) Compare BPSK, BFSK, QPSK w.r.t. [6M]
i) BW
ii) Probability of Error
iii) Bit Rate

b) Draw block diagram and Explain generation of QPSK with waveforms.[6M]

c) Explain M-ary QAM transmitter and receiver. [4M]

Q7) a) Define [4M]
i) Processing Gain
ii) Jamming Margin

b) The DSSS communication system has message bit duration (Tb) = 4.095ms and chip duration(Tc) = 1 μs. Calculate the processing gain and jamming margin if (Eb/No) = 10 and the average probability of error Pe = 0.5 × 10–5 [6M]

c) Draw the block diagram of DSSS system and explain various blocks. [8M]

OR

Q8) Write short note on [18M]

i) FHSS

ii) Properties of PN sequence

iii) Fast and slow frequency hoping

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