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EC2301    DIGITAL COMMUNICATION

UNIT – I
PART – A
1. Give an example for time limited and time unlimited signals.[MAY 2011]
2. Give the advantages and disadvantages of digital communication[May 2011]
3. Which parameter is called figure of merit of a digital communication system
and why?       [NOV 2010]
4. What is meant by distortion less transmission?              [NOV 2010]
5. Define BER
6. What are the advantages of PAM?
7. What is meant by basis set?
8. What is the condition for orthogonal?
9. Define noise equivalent bandwidth
10. State Dimensionality theorem
11. What is GSOP?
12. Write the expression for bandwidth of digital signal.
13. Write the expression for Linear filter channel.

PART-B
1. Explain how PWM and PPM signals are generated.(16 )              [MAY 2011]
2. Classify channels. Explain the mathematical model of any two communication channels (16)
[MAY 2011]
3. Draw a neat block diagram of a typical digital communication system and
explain the function of the key signal processing blocks.( 16)     [NOV 2010]
4. Distinguish between base band and bandpass signaling. (6)
5. Explain Binary symmetric channel and Gaussian channel with
their mathematical models. (10)               [NOV 2010]
6. Derive Geometrical representation  of  signal.(8)
7. Explain the procedure for obtaining from the basis set.(8)
8. Explain the mathematical models of communication channel
9. Explain the concept of PWM and PAM
10. Obtain the orthonormal basis function for the set of waveforms using GSOP

UNIT-II
PART-A
1. State sampling theorem.                                                                [MAY 2011]
2. What is quantization error                                                              [MAY 2011]
3. Why is prefiltering done before sampling?                                        [NOV 2010]
4. Define quantization noise power                                                      [NOV 2010]
5. State sampling theorem.  (MAY/JUN2006/MAY/JUN2007, APR/MAY2008, NOV 2008)
6. What are the limitations of delta modulation?   (APR/MAY2004,MAY/JUNE 2009)
7. What should be the pass band for anti aliasing and smoothing filters used with pulse
modulation / demodulation systems?      (NOV/DEC2004)
8. Why compressors are used in PCM?      (NOV/DEC2004)
9. What is the interpolatory property for sinc function?    (APR/MAY2005)
10. Draw the block diagram of transmitter and receiver sections of DPCM.   (APR/MAY2005,
MAY/JUNE 2009)
11. What do you under stand by the term aliasing?     (NOV/DEC2005)
12. A band pass signal has the spectral range that extends from 20 kHz to   82 kHz. Find the
acceptable range of sampling frequency fs.     (NOV/DEC2005)
13. What is the SNR of PCM system if number of quantization levels is 28
?  (MAY/JUN2006)
14. State bandpass sampling theorem     (MAY/JUNE 2006)
15. Define quantisation error.     (MAY/JUNE2007,NOV/DEC 2008)
16. )
17. A signal x(t)=5 cos (1000 Î t) is sampled and quantized using 8 bit PCM system. Find the signal
to quantization noise ratio      (NOV/DEC 2007)
18. State the principle of DPCM       (APR/MAY2008)
19. Plot the magnitude spectrum of the ideally sampled version of the signal M(t)=2 cos (200 Î t) +
40 sin (290 Î t). Assume that the sampling rate is 1 KHz.   (APR/MAY 2008)
20. Define pulse position modulation scheme with a suitable diagram.
21. Differentiate Noise and fading.       (NOV/DEC 2008)
22. An analog signal is quantized and transmitted by using a PCM system. If each sample at the
receiving end of the system must be known to within ± 0.5% of the peak to peak full scale
value. How many digits must each sample contain   (NOV/DEC 2008)
23. Define quantisation noise.      (NOV/DEC 2008)
24. State sampling theorem for lowpass signals.    (MAY/JUNE 2009)
25. What are the drawbacks of delta modulation.    (MAY/JUNE 2009)

PART-B
1. Explain a uniform quantization process(8).                                         [MAY 2011]
2. Write note on temporal waveform coding(8)                                         [MAY  2010]
3. Explain a spectral waveform encoding process (8)                                       [MAY 2011]
4. Compare various speeches encoding method(8)                                          [MAY 2011]
5. State the nyquist sampling theorem.Demonstrate its validity for an analog signal
having fourier transform x(f) which is zero outside the interval[-fm<f<+fm]  [DEC2010]
6. Explain in detail the various source coding  generating wideband FM with neat block diagram.
7. What is meant by compander? What are the two types of compression? (APR/MAY2004, 8 MARKS)
8. Explain the frame format and signaling scheme used in T1 carrier system.(APR/MAY2004,8 MARKS)
9. Draw the block diagram of differential PCM and explain the function performed by each block.
(NOV/DEC2004,8 MARKS)
10. What is meant by slope overload distortion in DM? What is the condition to be satisfied to avoid
this situation?        (NOV/DEC2004,8 MARKS)
11. With neat block diagram, explain in detail about delta modulation and the types of quantization
errors occurring in it.       (APR/MAY2005,12 MARKS)
12. With necessary sketches and expressions, briefly explain about flat top sampling.
(APR/MAY2005,8 MARKS)
13. With supporting derivation prove that if a signal contains no frequencies higher than W hertz, it
may be reconstructed from its samples at a sequence of points spaced 1/2W seconds apart.
(APR/MAY2005; MAY/JUN2006,8 MARKS)
14. Derive expressions for the quantization noise and signal to noise ratio in a PCM system using
uniform quantizer.        (NOV/DEC2005,10 MARKS)
15. A sinusoidal signal is transmitted using PCM. An output SNR of 55.8 dB is required. Find the
number of representation levels required to achieve this performance. (NOV/DEC2005,6
MARKS)
16. Derive the expression for SNR in PCM system and compare it with delta modulation. Explain
how SNR can be improved in a PCM system.     (MAY/JUN2006,10 MARKS)
17. Show that predication error variance is less than the variance of the predicator input for
predictior of order 1      (MAY/JUNE 2006 6 MARKS)
18. Explain the principle of delta modulation and derive an expression for average output noise
power in delta modulation.      (MAY/JUN2006,8 MARKS)
19. Explain the process of quantisation, encoding and decoding in PCM? In what way DPCM is better
than PCM?         (MAY / JUNE 2007)
20. Explain uniform and non uniform quantisation    (4 marks- APR/MAY2008)
21. Write notes on TDMA        (APR/MAY2008)
22. (i) Give the block diagram of differential pulse Code Modulation Scheme and explain the principles
in detail         (APR/MAY 2008 9 Marks)
a. (ii) Obtain an expression for the processing gain of a DPCM system  (APR/MAY 2008 4
MARKS)
b. (iii) Suppose an exesting standard PCM system for voice signal is replaced by a DPCM of
processing gain 6dB, while maintaining the (SNR)Q/ What will be the reduction in the bit
rate achieved by DPCM? (APR/MAY 2008 3 MARKS)
23. (i) For a uniform quantizer, discuss the way in which the number of quantization levels (L)
a. (ii) Discuss the need for Non-uniform quantization os speech signal  (APR/MAY 2008 2
MARKS)
b. (iii) Outline the principles of compander used for speech signal.  (APR/MAY 2008 4
MARKS)
c. (iv) Give the bit rate of a Delta modulator fed samples at a rate of 40ksamples/sec.
(APR/MAY 2008 2 MARKS)
d. (v) How does adaptive delta modulation help in alleviating the problems associated with
Delta modulation Scheme
24. Obtain an expression for the processing gain of a DPCM   (NOV/DEC2007)
25. How does ADM  allevates problems associated with DM   (NOV /DEC2007)
26. With neat diagram ,explain the detection of PWM signals.(8)                   (NOV /DEC2007)
27. Explain the two types of quantization noise in delta modulation system.(8) (NOV /DEC2007)
28. Draw the block diagram and explain the process of a PCM system in detail.
i. (NOV/DEC 2008-10 Marks)
29. Compare the principles of Delta and adaptive delta modulation systems.
i. (NOV/DEC 2008-6 Marks)
30. An analog voltage waveform having an absolute bandwidth of 100 Hz and an amplitude range
of –10 V o +10 V is to be transmied over a PCM system with ± 0.1% accuracy (full scale).
31. Determine the minimum sampling rate needed.(4)
32. Determine the number of bits needed in each PCM word.(4)
33. Determine the minimum bit rate required in the PCM signal.(4)
34. Determine the minimum absolute channel bandwidth required for transmission of this PCM
signal.(4)        (NOV/DEC 2008)
35. (i) Discuss the principle of Adaptive Delta modulation in detail.    (10)
(ii) Give an account of the advantages and limitations of PCM. (6) (MAY/JUNE 2009)
36. (i) Describe the concept of digital multiplexing and demultiplexing  (8)
(ii) Explain how PCM is influenced by noise sources.     (8) (MAY/JUNE 2009)
37. (i) A PCM system uses a uniform quantizer followed by a 7 bit binary encoder. The bit rate of
the system is equal to 50 × 106 bits per second.
(1) What is the maximum bandwidth for which the system operates
(2) satisfactorily?
(3) Determine the output signal to quantizing noise ratio when a full – load
(4) Sinusoidal modulating wave of frequency 1 MHz is applied to the
output.(8)
38. With neat diagram and necessary equations, explain the concept of sampling and
reconstruction of signals.(8)(MAY/JUNE 2009)
39. Explain the principle of Delta modulation and derive and expression for thermal
noise in delta modulation.(8)
40. What is the need for companding in PCM? Draw the transfer characteristics of a
companding system.(4)
41. With a neat diagram, explain the principle of TDMA  (4) (MAY/JUNE 2009)

UNIT-III
PART A
1. Define hamming distance.                                                                             (MAY 2011)
2. What is meant by transparency with respect to line codes                                 (MAY 2011)
3. Define hamming distance and calculate its value for two code words 11100 and 11011
(NOV 2010)
4. Draw the NRZ and RZ code for the digital data 10110001                                  (NOV 2010)
5. What is meant by syndrome of linear block code?     (APR/MAY2004)
6. How is the syndrome computed for block codes?       (NOV/DEC2004)
7. Draw the diagram of a convolutional encoder of rate ½ with generator polynomial:
g(1)(D)=1+D+D2  and g(2)(D)=1.        (NOV/DEC2004)
8. What does meant by RS coding?       (APR/MAY2005)
9. What is convolutional code?      (APR/MAY2005; MAY/JUN2006)
10. Explain the fundamental difference between block codes and convolutional codes.
(NOV/DEC2005,M
AY/JUNE 2009))
11. How will you define coding gain with reference to error control codes?   (NOV/DEC2005)
12. What is meant by BCH code?      (MAY/JUN2006, NOV /DEC2007)
13. List the advantages of turbo codes.      (MAY/JUN2007)
14. Define minimum distance.        (MAY/JUN2007)
15. Give the special features of Trellis code       (NOV /DEC2007)
16. Define linear block code.                                                                                 (NOV /DEC2007)
17. What is meant by constraint length of convolutional code?                                  (NOV /DEC2007)
18. Write 4 features of linear block codes       (APR/MAY2008)
15.Define Hamming distance of a block code.      (NOV/DEC 2008)
16.Show that the code C={000,100,011,111} is not cyclic.                                       (NOV/DEC 2008)
17.Define Hamming distance and hamming weight       (MAY/JUNE2009)
18.What are the error detection and error correction capabilities of Hamming Code? (MAY/JUNE
2009)
19.What are the fundamental properties exhibited by cyclic codes?                     (MAY/JUNE2009)
20.Define block hopping.                                                                                (MAY/JUNE2009)

PART-B
1. Assume a (2,1) convolutional coder with constraint length 6.Draw the tree diagram,state
diagram and trellis diagram for the assumed coder   (MAY 2011)
2. Find the (7,4) linear systematic block code word corresponding to 1101.Assume a suitable
generator matrix.                                                                 (MAY 2011)
3. Derive the power spectra of polar codes and on-off codes. Discuss their characteristics (16)
(MAY 2011)
4. For(6,3) systematic linear block code the codeword comprises I1,I2,I3,P1,P2,P3 where the 3
parity bits P1,P2,P3 are formed from the information bits as follows:
a. P1= I1Ó¨ I2
b. P2= I1 Ó¨ I3
c. P3= I2 Ó¨ I3
Find parity check matrix,generator matrix,all possible codewords, minimum weight
5. minimum distance ,the error correcting and detecting capability of the code.(MAY2010)
6. Explain how encoding is done by convolutional codes with a suitable example (MAY2010)
6. Explain tree diagram,trellis diagram and state transition diagram of convolutional codes
7. Write the generator matrix and parity check matrix of (7,4) hamming code.
i. (APR/MAY2004,6 MARKS)
8. Describe a decoding procedure for linear block code.   (APR/MAY2004,6 MARKS)
9. Draw the block diagram of rate ½ convolutional encoder with constraint length 3. What is
generator polynomial of the encoder? Find the encoded sequence you have drawn, corresponding
to the message (10011).      (APR/MAY2004,12 MARKS)
10. Obtain the trellis diagram of the encoder that you have drawn.  (APR/MAY2005,4 MARKS)
11. Draw the diagram of the ½ rate convolutional encoder with generator polynomial: g
(1)(D)=1+D and g(2)(D)=1+D+D2 . And compute the encoder output for input sequence 101101.
i. (NOV/DEC2004,10 MARKS)
12. What is meant by free distance of a convolutional code? How does it affect the number of errors
that can be corrected and coding gain?      (NOV/DEC2004,6 MARKS)
13. Briefly explain the viterbi-decoding algorithm.       (APR/MAY2005; MAY/JUN2005,APR/MAY2008)
14. Describe in detail about linear block codes.   (APR/MAY2005; MAY/JUN2006,4 MARKS)
15. Consider a rate ½ , non systematic convolutional code with, g(1) = {1,0,1} and g(2)={1,1,1}.
Determine the encoder output corresponding to the data sequence {1,0,1,0,1}. If the first and the
fourth bits of the encoded sequence are affected during transmission, demonstrate the error
correcting capability of the viterbi algorithm.     (NOV/DEC2005,16 MARKS)
16. A (15,5) linear cyclic code has a generator polynomial, g(D)=1+D+D
2+D4+D5+D8+D10  Draw the block diagrams of an encoder and syndrome calculator for this code. Find the code polynomial in the systematic form, for the message polynomial m(D)=1+D2+D4. Is y(D)=1+D4+D6+D8+D14, a code polynomial? If not, find the syndrome of y(D).
i. (NOV/DEC2005,16 MARKS)
17. Generate the code words for (7,4) hamming code.   (MAY/JUN2006, 8 MARKS)
18. State and prove the properties of syndrome decoding.   (APR/MAY2005,6 MARKS;
MAY/JUN2006,8 MARKS)
19. Explain the features of RS code.     (APR/MAY2004,4 MARKS)
20. Explain any four characteristics of the following block codes (i) BCH codes (ii) CRC codes (iii)
maximum length codes.      (NOV/DEC2004, 12 MARKS)
21. Find the generator and parity check matrix for (5,1) repetition code. (NOV/DEC2004,4 MARKS)
22. Evaluate the syndromes for all five probable signal error patterns in (5,1) repetition
code.(MAY/JUN2006,6 MARKS)
23. Let g(x) be the generarator polynomial of a cyclic code C. Find a scheme for encoding the data
sequence(d0 ,
d1, d2, …. dk-1 )into an (n,k) systematic code C.  (MAY/JUNE,2007/16MARKS)
24. Give the details of implementation of cyclic encoder and decoder based on linear feedback shift
registers                    (NOV /DEC2007)
25. Discuss the convolutional decoder algorithm in detail for the encoder of constraint length 3 and
code rate ½.        (NOV /DEC2007)
26. Prove that the minimum distance of a linear block code is equal to the minimum weight of any
non zero word in the code      (APR/MAY2008)
27. Explain the concept and design procedure of Viterbi decoding algorithm for a block
code.(NOV/DEC 2008)
28. A 1/3 rate convolutional code has the following generators:
a. g1=[1 0 0]; g2=[1 0 1] and g3=[1 1 1]
b. (1)Draw the encoder circuit corresponding to this code.     (2.5)
c. (2) Draw the state transition diagram for this code            (2.5)
d. (3) Draw the state diagram for this code.                         (2.5)
e. (4)Draw the Trellis diagram for this code.                         (2.5)
f. (5)  This code is used for transmission over a AWGN channel with hard decision
decoding. The output of the demodulation detector is (101001011110111…). Using
viterbi-decoding  algorithm, find the transmitted sequence. (NOV/DEC 2008)
29. (i) the parity check matrix of a particular (7,4) linear block code is given by
1    1    1    0    1    0    0
H=     1    1    0    1    0    1    0
1    0    1    1    0    0    1
Find the generator matrix.    (6)
(ii) Explain in detail the coding and decoding of linear block codes  (10)(MAY/JUNE 2009)
30. (i) For the convolutional coder show in figure, draw the state diagram and hence the trellis
diagram. The input sequence is 11010100. (8)
(ii) What are called cyclic codes? Explain with merits and demerits. (8)   (MAY/JUNE 2009)
26. (i) With necessary polynomial of a (7,4) cyclic code is g(x) = 1 + x + x3. Generate a
systematic code word for the message vector M = 1011.                                      (8)
31. (ii) State and prove any two properties of syndrome decoding.  (8)(MAY/JUNE 2009)
27. (i) The h sub matrix of a (7,4) systematic linear block code is given by

UNIT-IV
PART-A
1. What is a matched filter?                                                                      (MAY 2011)
2. Give 2 application for eye pattern?                                                       (MAY 2011)
3. What is the need for a demodulator in case of baseband signaling when the received are
already pulselike waveforms                                                                 (NOV 2010)
4. How does pulse shaping reduce ISI
5. What does the term equalization refer to? Explain how it is carried out by using transversal
filters?                                                                                                 (NOV 2010)
6. How is eye pattern obtained on the CRO?     (APR/MAY2004)
7. What is the condition for zero intersymbol interference?    (APR/MAY2004)
8. How is the transfer function of matched filter related to the spectrum of the input signal?
9. (APR/MAY2004)
10. A TDM signal with bit time of 0.5 Âµs is to be transmitted using a channel with raised cosine roll
off factor of 0.5. What is the bandwidth required?    (NOV/DEC2004)
11. From the eye pattern, how is the best time for sampling determined?
12. (NOV/DEC2004, NOV /DEC2007)
13. Why intersymbol interference takes place in a channel?    (APR/MAY 2005)
14. What is meant by” pseudoternary signaling”?                                        (APR/MAY 2005)
15. What is the purpose of using an eye pattern?   (NOV/DEC2005,APR/MAY2008)
16. Why do you need adaptive equalization in a switched telephone network? (NOV/DEC2005)
17. Draw an illustrative figure to show the operation of a correlation receiver. (NOV/DEC2005)
18. What is an ideal nyquist channel?      (MAY/JUN2006)
19. What is the need for equalization?      (MAY/JUNE2007)
20. Give the Nyquist criterion for zero ISI.      (NOV /DEC2007)
21. What is meant by intersymbol interference?   (MAY/JUN2006, APR/MAY2008)
22. 15. Why do we require equalization for a communication system?  (NOV/DEC 2008)
23. 16.List the applications of matched filters.                                     (NOV/DEC 2008)
24. 17.What do you mean by M-ary orthogonal signals?                                (NOV/DEC 2008)
25. 17.What is meant by matched filter?     (MAY/JUNE 2009)
26. 18.How do we get eye pattern? What do you infer from this?  (MAY/JUNE 2009)
27. 19.Draw the functional model of pass band data transmission.  (MAY/JUNE 2009)

PART-B
1. Derive the expression for bit error probability due to a matched filter(16)(MAY 2011)
2. Discuss on signal design for ISI illumination(16)(MAY 2011)
3. Define a matched filter and compare its functioning with a correlator(10)(NOV 2010)
4. Explain how a matched filter can maximize SNR for a given transmitted symbol(6)
5. What does the term equalization refer to? Explain how it is carried out by using transversal
filters?                                                                                (NOV 2010)
6. Sketch the time response and frequency response of signal with raised cosine pulse spectrum.
(APR/MAY2004,8 MARKS)
7. Why is precoding used with duo binary signaling scheme? Draw the block diagram of precoder and
explain its operation.        (APR/MAY2004,8 MARKS)
8. Draw the block diagram of an adaptive filter and explain the LMS algorithm. (APR/MAY2004,10
MARKS)
9. Explain how eye pattern is used to study the performance of a data transmission system.
(APR/MAY2004,6 MARKS)
10. What is meant by the ideal nyquist channel? What are its merits and limitations?
(NOV/DEC2004,8 MARKS)
11. Draw the block diagram of the duo binary signaling scheme and derive the overall frequency
response of this scheme.      (NOV/DEC2004, NOV /DEC2007)
12. Derive the equation for the impulse response coefficients of the zero forcing equalizer.
(NOV/DEC2004,8 MARKS)
13. Explain why adaptive equalizers are required for telephone channel (NOV/DEC2004, 4 MARKS)
14. With neat sketches, explain the duo binary signaling scheme. (APR/MAY2005,10 MARKS;
MAY/JUN2006,8 MARKS)
15. Obtain an expression for nyquist criterion for distortion less base band transmission for zero
intersymbol interference.     (APR/MAY2005,6 MARKS)
16. Write briefly about eye pattern and adaptive equalization for data transmission.
(APR/MAY2005,10 MARKS; MAY/JUN2006,8 MARKS)
17. What you understand by intersymbol interference (ISI)? Discuss in detail the nyquist criterion for
minimizing (ISI). Explain the difficulties in implementing it in a practical system.
(NOV/DEC2005,16 MARKS)
18. Discuss the merits and demerits of duo binary signaling.           (NOV/DEC2005,6 MARKS)
19. The binary data (0 1 1 1 0 0 1 0 1) are applied to the input of a duo binary encoder. Construct the
duo binary encoder output and the corresponding receiver output, without precoder. Suppose due
to error during transmission, the level produced by 3rd digit is reduced to zero, construct the new
receiver output.       (NOV/DEC2006,10 MARKS)
20. Discuss on (i) Adaptive equalization
i. (ii)Base band binary PAM system.     (MAY/JUNE2007)
21. Compare Base band binary PAM system with BFSK.    (NOV /DEC2007)
22. Derive the expression for probability of error for matched filter.(8)                      (NOV /DEC2007)
23. Draw the block diaram of adaptive equalisation and explain.(8)                           (NOV /DEC2007)
24. Explain Nyquist solutions to avoid ISI.       (APR/MAY2008)
25. Design a 3-tap equalizer to reduce ISI due to Pr (t).     (APR/MAY2008)
26. A baseband binary digital communication system transmits data at 1 kbps. The PSD of noise is
10-7  W/Hz and the received signal amplitude is 20mV.
27. Find the error probability for bipolar rectangular signaling.
28. If the bit rate is 10kbps to what value must A be adjusted in order o attain the same error
probability as in part (a).
29. What is the required channel bandwidth in case (b).
30. If not more than a 5kHz channel is available, What should be the value of A so that the data
rate is maximized and the error probability is same as in part (a).      (NOV/DEC 2008)
31. Explain on Correlative level coding and adaptive equalization of baseband transmission.
(NOV/DEC 2008)
32. (i) What is known as ISI? Discuss the cause for ISI. Also explain Nyquist criteria for distortionless
33. Transmissin. (10)
34. (ii) Write a note on Base band M-ary PAM transmission  (6)         (MAY/JUNE 2009)
35. 24.(i) describe Duobinary encoding. Also discuss how error propagation is eliminated.  (10)
36. (ii)Explain the two operation modes of adaptive equalizers  (6)         (MAY/JUNE 2009)
25. (i) A binary PAM wave is to be transmitted over a low pass channel with an
i. absolutely maximum bandwidth of 75 KHz. The bit duration in 10 msec. Find
ii. a raised cosine spectrum that satisfies these requirements.(6)
37. (ii) With neat sketches, explain the modified duo binary signaling scheme (10) (MAY/JUNE
2009)
26. (i) Write briefly about eye pattern and adaptive equalization for data transmission (10)
38. (ii) Compare the power spectra of different binary formats.(MAY/JUNE 2009)

UNIT-V
PART-A
1. Draw the PSK waveform for 011011                                                               (MAY 2011)
2. What is a non coherent  detection system                                                       (MAY 2011)
3. Define QAM and draw its constellation diagram                                               (NOV 2010)
4. A binary shift keying system employs 2 signalling frequencies f1 and f2. the  lower frequency
is  1200hz and signaling rate is 500 baud calculate f2                                         (NOV 2010)
5. In minimum shift keying what is the relation between the signal frequencies and bit rate?
(APR/MAY2004)
6. Write the expression for bit error rate for coherent binary FSK.               (NOV/DEC2004)
7. Bring out the difference between coherent and non-coherent binary modulation schemes.
(APR/MAY2005)
8. What is the error probability of MSK and DPSK?      (APR/MAY2005)
9. Highlight the major difference between QPSK signal and a MSK signal.   (NOV/DEC2005)
10. Compare the probability of error of PSK with that of FSK.  (MAY/JUN2006, NOV /DEC2007)
11. State the difference between coherent and non-coherent binary modulation techniques.
i. (MAY/JUN2006)
12. What do you understand by continuous phase frequency shift keying?   (MAY/JUN2007)
13. Give the signal space representation of QPSK      (NOV /DEC2007)
14. What is a matched filter?        (APR/MAY2008)
15. What is the need for synchronization?       (APR/MAY2008)
16. What is signal constellation diagram?      (NOV/DEC 2008)
17. State Shannon’s theorem on channel capacity.      (NOV/DEC 2008)
18. What is signal constellation diagram?                                                       (NOV/DEC 2008)
19. Differentiate coherent and non-coherent detection.                      (NOV/DEC 2008)

PART-B
1. Derive the bit error probability due to coherent ASK,PSK & FSK systems. Compare the
2. Performance                                                                                       (MAY 2011)
3. Discuss QPSK Signalling
4. Discuss bit error probability due to QPSK receiver.Compare it with PSK receiver(MAY 2011)
5. Distinguish coherent and non coherent scheme                                          (NOV 2010)
6. Discuss Noncoherent detection method of BFSK Signalling                            (NOV 2010)
7. What do you understand by coherent detection?    (APR/MAY2004,2 MARKS)
8. Discuss the method of bit synchronization.     (APR/MAY2004,6 MARKS)
9. Draw the block diagram of QPSK transmitter and coherent QPSK receiver and explain their
operation.     (APR/MAY2004,10 MARKS;MAY/JUN2006, NOV /DEC2007)
10. Compare the BER of coherent PSK, coherent QPSK and coherent FSK.  (APR/MAY2004,6 MARKS)
11. Draw the block diagram of MSK transmitter and explain the function of each
block.(NOV/DEC2004,8 MARKS)
12. Explain how MSK signal is obtained from CPSK signal?    (NOV/DEC2004,8 MARKS)
13. With necessary equations and signal space diagram, obtain the probability of error for coherent
binary FSK systems.       (APR/MAY2005,12 MARKS)
14. Draw the block diagram of a QPSK receiver and explain its working. (APR/MAY2005,4 MARKS)
15. With neat block diagram, explain briefly how symbol synchronization is achieved? (APR/MAY2005,8
MARKS)
16. Discuss briefly about minimum shift keying for a CPSK signal. (APR/MAY2005;MAY/JUN2006,8
MARKS)
17. Explain BPSK signal transmission and coherent BPSK reception with suitable diagrams. Derive an expression for the probability of symbol error for the scheme.  (NOV/DEC2005,16 MARKS)
18. With necessary equations and signal space diagram, explain briefly about FSK system.
(MAY/JUN2006, NOV /DEC2007, APR/MAY2008)
19. Obtain probability of error in terms of Eb/N0 for QPSK.   (MAY/JUN2006, APR/MAY2008)
20. Draw the block diagram of MSK transmitter and explain the function of each blockwith the
constellation diagram.                 (MAY/JUNE,2007/ 16MARKS)
21. What are the advantages and disadvantages of MSK as compared to QPSK system?(6) (NOV
/DEC2007)
22. (1)Explain carrier synchronization in QPSK signal.(6)
23. (ii)Explain the detection of binary FSK signal with block diagram.(7)
24. (iii)Explain binary PSK signal with geometrical representation.(3)             (NOV /DEC2007)
25. Explain the working of carrier synchronization system    (APR/MAY2008)
26. Draw the block diagrams of MSK transmitter and receiver and explain the functions of each block.
Draw the constellation diagram. Derive probability of error.         (NOV/DEC 2008)
27. Binary data are transmitted over a microwave link at the rate of 1 Mbps and the PSD of the noise
at the receiver input is 10-10W/Hz. For each of the following pairs, determine which one requires
more power than the other. Determine the extra average signal power required by the more power
consuming scheme so that an average probability of error of 10-4 is always maintained.
28. Coherent PSK and DPSK. (4)
29. Coherent FSK and non-coherent FSK. (4)
30. Coherent PSK and QPSK. (4)
31. Coherent FSK and coherent MSK.   (4)                     (NOV/DEC 2008)
32. Explain the generation, detection, signal space diagram, bit error probability and power spectra of
QPSK.  (16)           (MAY/JUNE 2009)
33. (i) Enumerate on carrier and symbol synchronization  (10)
34. (ii) Compare the Digital modulation techniques in terms of bit error rate and bandwidth efficiency.
(6)         (MAY/JUNE 2009)
35. (i) An RSK system transmits binary data at the rate of 2.5 × 106  bits per second. During
36. the course of the transmission, white Gaussian noise of zero mean and power
37. spectral density 10-20 watts per hertz in added to the signal. In the absence of noise,
38. the amplitude of the received sinusoidal wave of digit 1 or 0 is 1 microvolt.
39. Determine the average probability of symbol error, assuming coherent detection. (8)
40. (ii) Discuss briefly about Minimum Shift Keying for a CPFSK signal.
(8)(MAY/JUNE 2009)
41. With necessary equations and signal space diagram, obtain the probability of error for
coherent binary PSK system.

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