### EC1351 DIGITAL COMMUNICATION–Important Questions 2012 Edition

Anna University
Department of Electronics Communication Engineering

Department : B.E ECE
Semester : V
Year : 3rd yr
Regulation : 2008
Subject Code : EC1351

Subject Name : DIGITAL COMMUNICATION

Content : EC1351-DIGITAL COMMUNICATION – Important Questions 2012 Edition

UNIT-1

PULSE MODULATION

1. Drive the expression for the sampling process in time domain. (16)

2. What are all the types of sampling technique and explain about any two. (16)

3. a. Explain the generation of PPM and PWM with neat circuit diagram. (8)

b. Explain the quantization process with PCM block diagram. (8)

4. Write brief notes on 1) TDMA (8 )

2) FDMA (8)

5. Compare DM with ADM and explain linear prediction filter. (16)

UNIT -2

BASEBAND PULSE TRANSMISSION

1. Derive the expression for the matched filter and prove any one property. (16)

2. Prove the effect ISI using necessary block diagram and design. (16)

3. Write brief notes on Nyquist‟s criterion for distortion less base band binary transmission. (16)

4. Explain the six array PAL transmission. (16)

5. Why do we use adoptive equalizer and design any one type of adoptive equalizer. (16)

UNIT - 3

PASSBAND DATA TRANSMISSION

1. Derive the expression for the BPSK technique. (16)

2. Explain the MFSK and derive the pe. (16)

3. Draw the space diagram of MSK and explain about the same. (16)

4. Derive the error probability expression for the MPSK. (16)

5. Compare the all types of Passband transmission. (16)

Unit- 4

ERROR CONTROL CODING

1. Explain the channel coding technique used in the Block codes. (16)

2. What are all the message vectors can be extracted from the code vector that was generated by 1+X+X3. (16)

3. Explain the Viterbi algorithm for the detection of any two message vectors (One Word) from the code vectors that were generated by (111), (101) and (011). (16)

4. Explain the construction of Block Code and Explain how error syndrome is calculated. (16)

5. Explain in detail about Orthogonal codes, Biorthogonal codes and Transorthogonal codes. (16)

UNIT- 5

1. Generate the PN sequence for [5, 4, 3, 1] and prove the all properties of the same. (16)

2. List out and prove the Properties of the PN sequence. (16)

3. Explain the concept of DS/BPSK. (16)

4. List out the uses of the FH. Explain the FH techniques with the frequency spectrum. (16)

5. Write shorts notes on

1. Probability Error. (4)

2. Jamming Margin (4)

3. (S/N) of the DS System. (8)