DIGITAL AND DATA COMMUNICATION
EC28505
SESSION 2024 - 25
Submitted to:-
1) Dr. Neetesh Purohit
2) Mr. Neeraj Malviya
3) Dr. Jaya Deepti Lal
Prepared by:-
1) Harish Gupta - 0801IT231050
2) Gourav Solanki- 0801IT231049
3) Meet Lahori - 0801IT231075
4) Aman Romade - 0801IT231020
5) Ansh Lanjhiwar - 0801IT231028
6) Harshit Gotre - 0801It231054
7) Akshat Jaishwal - 0801IT231018
8) Ashutosh Patkar- 0801IT231038
Question Paper
Unit -1
1. Differentiate between low-pass and high-pass filters.(2)
2. What is power spectral density (PSD) and why is it important?(2)
3.A signal x(t)=5cos(100πt)+3sin(200πt) is given.
(a) Determine the fundamental frequency of the signal. (3)
(b) Find its total power.
4. Describe modulation and demodulation in analog signals. (7)
Explain AM, FM, and PM with suitable diagrams and examples.
Unit-2
a) Define line coding and mention its necessity in digital communication. (2 marks)
b) What is Inter-Symbol Interference (ISI)? How does it affect signal transmission? (2 marks)
c) Explain the eye diagram and its role in detecting signal distortion. (3 marks)
d) Describe different types of line coding techniques with their advantages and disadvantages.
(7 marks)
OR
e) Explain the optimum detection of signals in noise using matched filter detection. (7 marks)
UNIT 3
Question 1 (2 Marks):
Define Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK). How
does the number of bits per symbol differ between BPSK and QPSK?
Question 2 (2 Marks):
What is the key difference between Frequency Hop Spread Spectrum (FHSS) and Direct
Sequence Spread Spectrum (DSSS) in terms of their approach to spreading the signal?
Question 3 (3 Marks):
Explain the concept of Power Spectral Density (PSD) in the context of digital modulation
schemes. How does the PSD of BPSK differ from that of QPSK?
Question 4 (7 mark)
a) Derive the probability of error for BPSK in an Additive White Gaussian Noise (AWGN)
channel. (4 marks)
b) Compare the probability of error of BPSK with that of QPSK, and explain why QPSK might be
preferred despite its error performance. (3 marks)
Or
Question 5 (7 Marks):
a) Explain the working principle of Direct Sequence Spread Spectrum (DSSS) and its
advantages in combating interference. (3 marks)
b) Consider a BPSK-modulated DSSS system with a spreading factor of 7 (i.e., the chip rate is 7
times the bit rate). If the bit energy-to-noise ratio ( E_b/N_0 ) is 10 dB without spreading,
calculate the effective ( E_b/N_0 ) after despreading at the receiver, and discuss how this
impacts the probability of error. (4 marks)
Unit 4
Q.1 Briefly explain the concept of "entropy" in the context of information theory.(2)
Q.2 What is the significance of "channel capacity" in a communication system?(2)
Q.3 Explain the trade-off between bandwidth and signal-to-noise ratio (S/N) as described by
Shannon's theorem.(3)
Q.4 Discuss the fundamental principles of linear block codes, cyclic codes, and convolutional
codes. Highlight the key differences between these coding techniques and provide a scenario
where each might be particularly advantageous.(7)
OR
Q.5 Explain the purpose of source encoding and channel coding in a digital communication
system. Discuss the objectives and techniques associated with each, and illustrate how they
work together to ensure reliable transmission of information. Provide specific examples of
source coding and channel coding methods.(7)
Unit-5
1.What is latency and how does it affect data transmission. (2)
2.Define jitter and its impact on real-time communication.(2)
3.A TDM system multiplexes 4 signals, each with a bandwidth of 5 kHz. If a guard band of (3)
1 kHz is required between channels, determine the minimum bandwidth required for
transmission.
4.(a) Explain the concept of Multiplexing and its types (FDM, TDM, WDM) with (7)
suitable diagrams.
(b) How does Error Detection and Correction work? Explain CRC and Hamming Code with
examples.
