1. JSS Academy of Technical Education, Noida
Department of Electronics & Communication
B. Tech 6th
CIA–III, AY 2017-18
Subject: Digital Communication, Subject Code: NEC 602
Time: 2 Hrs Total Marks 60
Course Outcomes
CO1 (C314.1) Define data formatting and digital carrier systems.
CO2 (C314.2) Explain statistical analysis of random signals and processes.
CO3 (C314.1) Illustrate the performance of matched filter with different modulation schemes.
CO4 (C314.1) Analyze different spectrum sharing techniques to enhance channel capacity.
CO5 (C314.1) Assess different channel error-correcting and detecting method.
PARTA: Attempt All Questions 5 x 2 =10
1. List the advantage of digital communication over Analog Communication. CO1
2. Three regular dice are thrown. Find the probability for the sum of the points appearing on the three
dice is 4. CO2
3. Draw the block diagram of Correlator detector. CO3
4. Why the FHSS signals adopt M-ary FSK modulation instead of efficient PSK or QAM? CO4
5. High resolution black & white pictures consist of about 2X106 picture elements & 16 different
brightness levels. Pictures are repeated at the rate of 32 per sec. All picture elements are assumed to be
independent & all levels have equal likelihood of occurrence. Calculate the average rate of information
conveyed by this TV picture source. CO5
PART B: Attempt ANY FOUR Question 4 x 5 = 20
6. Draw the block diagram of Digital communication and the list the methods for timing synchronization
in digital receiver. CO1
7. State and prove Chebyshev’s inequality. CO2
8. Derive the probability of error for polar signaling. CO3
9. How the PN Sequence is generated? Explain the properties of PN Sequence. CO4
10. A zero memory source emits six messages with probabilities 0.3, 0.25, 0.15, 0.12, 0.10, 0.08. Find 4-
ary Huffman code. Determine its average word length, the efficiency and the redundancy. CO4
PART C: Attempt ANY TWO Questions 2 x 15= 30
11a. Draw and explain block diagram of frequency hopping spread spectrum (FHSS) system. Show that
FHSS signal is more resistance to jamming signal. CO4
11b. List the properties of PDF. The pdf of a random variable X is given by CO2
pX(x) = k a ≤x ≤ b, where k is a constant
= 0 otherwise
(i) Determine the value of the k (ii) Let a= -1 and b=2. Calculate P (|X|≤ c) for c=1/2
12a. A parity code has the parity check matrix CO 5
H=
1 0 1 1 0 0
1 1 0 0 1 0
0 1 1 0 0 1
a Determine the generator matrix G
b Find the code word that begins with 101…….
c Suppose that the received code word is 110110. Decode this received word.
12b.Derive the optimum SNR for the Matched filter. CO3
13a. What is Near Far effect in CDMA? How it is overcome? Explain the OFDM with lock diagram.
13b. Sketch the state and tree diagram for the convolution encoder shown in fig. CO 5
