S 1 S 2 B.E. (Electronics Engineering / Elect ... · N IR /K W /18/3466/3471 2 3. a) A zero memoryless source emits m1 and m2 with probabilities 0.8 and 0.2 respectively. Find the

NIR/KW/18/3466/3471 1 P.T.O

B.E. (Electronics Engineering / Elect. Telecommunication / Elect. Communication Engineering)

Sixth Semester (C.B.S.) Digital Communication

P. Pages : 2 NIR/KW/18/3466/3471

Time : Three Hours Max. Marks : 80

_____________________________________________________________________

Notes : 1. All questions carry marks as indicated.

2. Solve Question 1 OR Questions No. 2.






8. Due credit will be given to neatness and adequate dimensions.

9. Assume suitable data whenever necessary.

10. Illustrate your answers whenever necessary with the help of neat sketches.

11. Use of non programmable calculator is permitted.

1. a) A random process provides measurements x between the values 0 and 1 with PDF given

as 3 2xf (x) 12x 21x 10x= − + for 0 x 1 ,

Determine (i) 12

P x (ii) 12

P x .

6

b) Explain Correlation Receiver in detail.

OR

7

2. a) State and prove central limit theorem.

5

b) Consider the given signals 1 2 3S (t),S (t),S (t) and 4S (t) as shown in fig. Find orthonormal

basis functions for this set of signals using Gram-Schmidt orthogonalization procedure.

S1(t)

t20

1

S2(t)

t2

0

1

1

-1

S3(t)

t3

0

1

2

-1

S4(t)

03

-1

t

8

*1291*

NIR/KW/18/3466/3471 2

3. a) A zero memoryless source emits 1m and 2m with probabilities 0.8 and 0.2 respectively.

Find the optimum binary code for this source as well as for its 2nd and 3rd order extension.

Determine code efficiency in each case.

8

b) Explain Adaptive transform coding.

OR

5

4. a) Consider the binary sequence :

1010110100100111010100001100111010100011011

6

b) Write short note on ADPCM.

7

5. a) Explain QPSK transmitter and receiver.

6

b) Explain generation and detection of DPSK in detail.

OR

7

6. a) Explain MSK transmitter and receiver.

7

b) Explain CPFSK in detail.

6

7. a) Explain Automatic Repeat Request System (ARQ) for error control.

6

b) Obtain the field elements of 4GF(2 ) whose modulo polynomial is given by

4P(x) x x 1= + + . Determine the conjugates of 7 in 4GF(2 ) . Also obtain its minimal

polynomial.

OR

8

8. A 1/3 rate convolutional encoder is described by 1 2g [1 0 0], g [1 0 1]= = and 3g [111]=

(i) Draw encoder corresponding to this code. (ii) Draw code tree (iii) Draw state transition

diagram. (iv) Draw trellis diagram. (v) Determine the expression for transfer function and

find the free distance for this code.

14

9. a) Explain Trellis coded modulation encoder in detail.

7

b) Write short note on LDPC coding.

OR

6

10. Find the generator polynomial of the double error correcting Reed – Solomon code of length 32 1− with symbols from 3GF(2 ) generated by 3P(x) x x 1= + + . For the above generator

polynomial if message polynomial is 4 4 2a(x) x= + . Find codeword polynomial and

code vector.

13

11. a) A four – stage shift register with feedback connections taken from the outputs of stages 4

and 1 through modulo – 2 adder, is used for PN sequence generation. Assuming the initial

contents of the shift register to be 0100, determine the output sequence. What is the length

of the sequence? Demonstrate its balance and run properties.

7

b) What is spread spectrum? Explain DS – SS in detail with mathematical analysis.

OR

7

12. a) Explain slow and fast frequency hopping with block diagram and suitable example.

9

b) A spread spectrum communication has following parameters,

Information bit duration, bT 4.095msec= PN chip duration, CT 1 sec=

Find processing gain and jamming margin in dB given that b

o

E10

N= .

************

5

TKN/KS/16/7470/7475 1 P.T.O

B.E. (Electronics Engineering / Electronics Telecommunication / Electronics Communication

Engineering) Sixth Semester (C.B.S.) Digital Communication

P. Pages : 2 TKN/KS/16/7470/7475


_____________________________________________________________________












1. a) The CDF for a certain random variable is given as,

x10k100

10x0kx

0x0

)x(F 2x

i) Find the value of k; ii) Find the value of )5x(P

iii) Find the value of ;)7x5(P iv) Find the expression for PDF.

8

b) State and explain Central-Limit Theorem.

5

OR

2. a) Consider the given signals )t(Sand)t(S),t(S,)t(S 4321 as shown in figure. Find

orthonormal basis functions for this set of signals. Using Gram-Schmidt orthogonalization

procedure.

S1(t)

1

0

3T

t

S2(t)

1

0

3T2

S3(t)

0

3T

t t

T

S4(t)

1

0T

7

b) Explain the concept of matched filter in detail.

6

3. a) A zero memory source emits messages 321 xandx,x with probabilities 0.45, 0.35 and 0.2

respectively. Find optimum (Huffman) binary code for this source as well as for its second

order extension (i.e. for N = 2). Determine code efficiency in each case.

8

b) Explain Adaptive Transform coding.

5

OR

4. a) Find L – Z source code for the binary source sequence given below:

10101101001001110101000011001110101100011011

7

b) With the help of block diagram explain CELP coding.

6

*0840*

NagpurStudents.Org

TKN/KS/16/7470/7475 2

5. a) Explain generation and detection of DPSK in detail.

7

b) Explain MSK transmitter and receiver.

6

OR


7

b) Explain CPFSK. Draw its signal space diagram.

6

7. a) Obtain the field elements of )2(GF 3 whose modulo polynomial is, 1xx)x(P 3 .

Show that 5 is primitive element of )2(GF 3 .

10

b) Explain Automatic Repeat Request (ARQ) for error control. 4

OR

8. A convolutional code is described by:

111gand101g;001g 321

i) Draw the encoder corresponding to this code.

ii) Draw the code tree for this code

iii) Draw the state transition diagram for this code.

iv) Draw the Trellis diagram for this code

v) The output of demodulator detector is (101001011110111), using Viterbi algorithm

find transmitted sequence.

14

9. a) Explain Trellis coded modulation encoder in detail.

6

b) Explain Turbo encoding and decoding with suitable block diagram. 7

OR

10. a) What are the different parameters of Reed solomon codes and obtain the generator

polynomial for (7 , 3) double error correcting R – S code using )2(GF 3 whose modulo

polynomial is .1xx3

8

b) Write a note on LDPC codes.

5

11. a) What is spread spectrum? Explain DS-SS technique in detail.

10

b) A spread spectrum communication has the following parameters:

Information bit duration ;.secm095.4Tb PN Chip duration .sec1Tc

Find processing gain and jamming margin in dB given that 10N

E

o

b .

4

OR

12. a) Figure shows four stage feedback shift register. The initial state is 1000. Find the output

sequence of shift register. Demonstrate the balance and run property of PN sequence. Also

plot autocorrelation function of PN sequence produced by this shift register.

+

Flip - flopOutput

Modulo -2 adder

8

b) Explain slow frequency hopping with suitable example. Draw its black diagram. 6

*********

NagpurStudents.Org

NKT/KS/17/7382/7387 1 P.T.O

B.E.Sixth Semester (Electronics Engineering / Electronics Telecommunication /

Electronics Communication Engineering) (C.B.S.) Digital Communication

P. Pages : 2 NKT/KS/17/7382/7387


_____________________________________________________________________









1. a) State and explain central limit theorem.

7

b) Probability density function is given by 1x1be.axFx , where 'X' is a random variable

whose allowable values range from .to

Find:

i) Relationship between a and b.

ii) CDF

iii) .2x1P

OR

7

2. a) Explain Gram Schmitt orthogonalization procedure.

7

b) Explain the concept of matched filter with its properties.

7

3. a) A memoryless source emits six messages with probabilities 0.3, 0.25, 0.15, 0.12, 0.1 and

0.08. Find entropy of source, obtain compact binary code. Find average length of code and

code efficiency.

7

b) Write short note on CELP coding.

OR

6

4. a) Consider the following binary sequence. 11101001100010110100. Use the Lempel- Ziv

algorithm to encode this sequence. Assume that the binary symbols 0 & 1 are already in

code list.

6

b) Explain Adaptive Subband coding.

7

*0346* NapurStudents.Org

NKT/KS/17/7382/7387 2


7

b) Write short note on memory less modulations methods.

OR

6

6. a) Explain DPSK transmitter and receiver.

6

b) Explain the continuous phase FSK (CPFSK). Draw its signal Space diagram.

7

7. a) Construct the Galoss field is GF (24) whose modulo polynomial is given as .1XX4

Determine the minimal polynomial for the elements only for 53 & for above case.

7

b) Explain Automatic repeat request system.

OR

7

8. a) A rate 3

1 convolutional encoder is described by.

;111g

;101g

;100g

3

2

1

Find:


ii) Draw the state diagram.

iii) Draw the code trellis diagram.

9

b) Explain Fano algorithm in detail.

5

9. a) Explain the concept of Turbo coding.

7

b) Explain Reed Solomon codes.

OR

6

10. a) Explain Trellis coded modulation.

6

b) Explain the concept of low density parity check coding.

7

11. a) What is the spread spectrum modulation? Give its application.

7

b) What is CDMA techniques and what are the different advantages of it.

OR

6

12. a) Explain DS-SS system with suitable transmitter and receiver diagram.

7

b) What is frequency hopping? Explain fast frequency hopping system. 6

************

NapurStudents.Org

NRJ/KW/17/4521/4526 1 P.T.O

B.E. (Electronics Engineering / Electronics Telecommunication /

Electronics Communication Engineering) Sixth Semester (C.B.S.) Digital Communication

P. Pages : 2 NRJ/KW/17/4521/4526


_____________________________________________________________________












1. a) Explain Digital communication system with the help of block diagram.

7

b) State and explain central limit theorem. 6

OR

2. a) Show that maximum signal component occurs at t = T and has magnitude E, i. e energy of

the signal x(t)

4

b) Consider the given signals )t(Sand)t(S),t(S),t(S 4321 as shown in fig. given below. Find

orthonormal basis functions for this sets of signals using gram Schmidt orthogonalization

procedure.

S1(t)

1

0 T/3 t

S2(t)

1

0 2T/3 t

S3(t)

1

T

S4(t)

1

0 T t3

T t

9

3. a) Consider a DMS with alphabets 321 S,S,S with probabilities{0.45, 0.35, 0.20}

respectively

a) Find average codeword length of the Huffman code

b) Let the source be extended of order number two. Apply the Huffman's algorithm to

the resulting extended source. Determine the average codeword length of new code

and its entropy

c) Compare the average code word length calculated in part b with entropy of original

source.

9

b) State and explain Kraft Mcmillan Inequality. 4

OR

4. a) Find the LZ source coding for the given sequence.

11101001100010110100

Assume that the binary symbols 0 & 1 are already in the code book.

6

*0120* NagpurStudents.Org

NRJ/KW/17/4521/4526 2

b) Explain scalar and vector quantization in detail.

7

5. a) Explain coherent binary phase shift keying technique with the help of block diagram and

mathematical equations.

9

b) Write short note on Gaussian Minimum shift keying Technique. 5

OR

6. a) Write short note on memory less modulation method.

7

b) Explain quadrature phase shift keying transmitter and receiver.

7

7. a) Construct the galal's field for of (2)

7

b) A rate

3

1 convolutional encoder is described by, ]100[gand]011[g]101[g 321 .

Determine the expression for transfer function.

7

OR

8. a) A rate 2/3 convolutional encoder is described by,

]0101[gand]1011[g]1101[g 321


ii) Draw the code tree for this code.

iii) Draw the state transition diagram for this code.

iv) Draw the trellis diagram for this code

14

9. a) Explain low density parity check coding.

7

b) Write short note on turbo coding. 6

OR

10. a) Write short note on Reed Solomon codes.

6

b) The (7, 3) RS code is a double error correcting code Using of (23) determine the generator

polynomial of the code and transmitted code vector j and m(x) is 243 xx

7

11. a) Write down the properties of pseudo noise sequence.

6

b) Explain in detail, slow and fast frequency hopping with suitable example.

7

OR

12. a) Explain direct sequence spread spectrum in detail.

7

b) Consider a maximum length sequence requiring the use of linear feedback shift register of

length 5. The set of feedback tab is [5, 2]

i) Draw the corresponding configuration of code generator.

ii) Assuming the initial state is 10000 Evaluate one period of maximum length sequence

generated by this scheme.

6

*********

NagpurStudents.Org

KNT/KW/16/7382/7387 1 P.T.O

B.E. Sixth Semester (Electronics Engineering/ Electronics Telecommunication /

Electronic Communication Engineering) (C.B.S.) Digital Communication

P. Pages : 3 KNT/KW/16/7382/7387


_____________________________________________________________________










10. Diagrams and chemical equations should be given whenever necessary.



1. a) Draw & explain basic block diagram of digital communication system.

7

b) Explain the central Limit Theorem.

6

OR

2. a) Consider the signals tS&tS,tS,tS 4321 as shown in figure below:

1

0

3

T2 t

)t(S1

1

0 tT

)t(S2

0 tT/3

)t(S3

0 t

)t(S4

3

T T

Using the Gram-Schmidt orthogonalization procedure find the orthonormal basis functions

of the above signal set.

7

b) Explain the concept of Matched Filter Receiver with its properties.

6

3. a) A discrete memoryless source S, produces the symbols A, B & C with probabilities

350&250,40 respectively.

a) Design a Huffman code for this source and determine its coding efficiency.

b) Design a Huffman code for the second order extension of this source and find the

average length of the code word for this code. What is the coding efficiency ?

7

b) Explain the concept of scalar & vector quantization.

6

OR

*0097*

www.solve

out.in

KNT/KW/16/7382/7387 2

4. a) Write a note on any two.

i) Adaptive sub band coding

ii) LP & CELP coding

iii) ADPCM

6

b) Encode the following binary sequence using Lempel - Ziv coding scheme

111010011000101.

Assume that binary symbols 0 & 1 are already there in the code book.

7

5. a) Explain QPSK transmitter & receiver with waveforms & signal space representations of

QPSK signals.

8

b) The binary sequence 1100100010 is applied to the following transmitted of modulation

system. Sketch the resulting waveform at the transmitter output for.

i) DPSK

ii) BPSK & BFSK

6

OR

6. a) Explain the MSK system in detail.

8

b) Write a note on:

i) Linear & non-linear modulation with examples.

ii) CPM

6

7. a) Construct the Galois field i.e. 42GF whose modulo polynomial is given by 1xx4 .

Determine the minimal polynomial for the elements only for 53 & for the above case.

7

b) Explain the different types of error control strategies & compare them.

7

OR

8. A rate

3

1 conventional encoder has the generator vectors as

111g,101g,001g 321

i) Draw the block diagram of the encoder

ii) Draw the code Tree

iii) Draw the Trellis Diagram

iv) Using Viterbi Algorithm find most likely data sequence if the received sequence is

(111, 101, 010, 111).

14

9. a) Explain the Trellis code Modulation concept with block diagram. Also illustrate the

partitioning of 16QAM - constellation.

8

b) Write a note on Turbo coding. 5

OR

www.solve

out.in

KNT/KW/16/7382/7387 3 P.T.O

10. a) What are the different parameters of Reed-Solomon codes & obtain the generator

polynomial for (7, 3) double - error correcting R S code using 32GF whose modulo

polymial is 1XX3 .

8

b) Write a note on LDPC codes.

5

11. a) Explain the generation of PN sequence with any example & also explain the properties of

the same.

5

b) Explain the FHSS system in detail with slow & fast frequency hopping.

8

OR

12. Write a note on any two.

i) CDMA

ii) OFDM

iii) Synchronization method for spread spectrum system.

13

**********

www.solve

out.in

KNT/KW/16/7382/7387 4

www.solve

out.in

Documents

S 1 S 2 B.E. (Electronics Engineering / Elect ... · N IR /K W /18/3466/3471 2 3. a) A zero memoryless source emits m1 and m2 with probabilities 0.8 and 0.2 respectively. Find the