ec2252 communication theory

EC2252 – COMMUNICATION THEORY III Sem ECE – R.Vanitha Asst.Prof./ECE

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MAHALAKSHMI ENGINEERING COLLEGE

TIRUCHIRAPALLI – 621213

QUESTION BANK

DEPARTMENT: ECE SEMESTER: IV

SUBJECT CODE / Name: EC2252 – COMMUNICATION THEORY

UNIT-I AMPLITUDE MODULATION SYSTEMS

PART -A (2 Marks)

1. Define Modulation Index for an AM Signal (AUC MAY 2010) (AUC MAY 2006)

2. What is the mid frequency of IF section of AM receivers and its bandwidth

(AUC NOV 2006)

3. Draw the circuit of an envelope detector. (AUC NOV 2007)

4. State any important spectral properties of periodic power signals (AUC NOV 2007)

5. Define Amplitude Modulation. Give the expression for AM wave (AUC NOV 2007)

6. Give the applications of SSBSC-AM. (AUC NOV 2007)

7. Compare low level modulation and high level modulation. (AUC NOV 2007)

8. A transmitter radiates 9 KW without modulation and 10.125 KW after modulation.

Determine depth of modulation. (AUC NOV 2007)

9. A 2 MHz carrier having amplitude of 5V is modulated by a 4 KHz audio signal having

amplitude of 2V. Determine the modulation index and draw frequency spectrum of

amplitude modulated wave. (AUC MAY 2008)

10. SSB is suitable for speech signals and not for video signals. Why?

(AUC MAY 2008)

11. A 500 W carrier modulated to a depth of 60 percent. Calculate the total power in

modulated wave. (AUC NOV 2008)

12. Define vestigial sideband transmission. Mention its application. (AUC NOV 2008)

13. Compute the bandwidth of the Amplitude modulated signal

a. C(t)=23*cos (230000πt)[1+0.8*cos (310πt)] (AUC MAY 2009)

14. Define AM and its spectrum (AUC MAY 2009)

15. An AM DSB-FC wave with a peak unmodulated carrier voltage AC=10V, a load

resistor RL=10Ώ and the modulation index m=1. Determine the total power of the

modulated wave. (AUC MAY 2009)

WWW.VIDYARTHIPLUS.COM


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16. How many AM broadcast stations can be accommodated i n a 100 kHz bandwidth if t

he highest frequency modulating a carrier i s 5 kHz? (AUC MAY 2010)

17. What are the causes of linear distortion? AUC MAY 2010)

18. How many AM broadcast stations can be accommodated in a 100 kHz bandwidth

(AUC DEC 2010)

19. If the highest frequency modulating a carrier i s 5 kHz?

20. State the applications of FDM (AUC DEC 2010)

21. What are the advantage of VSB (AUC MAY 2011)

22. Calculate the local oscillator frequency if incoming frequency is f1 and translated

carrier frequency (AUC MAY 2011)

23. How many AM broadcast stations can be accommodated i n a 100 kHz bandwidth

if the highest frequency modulating a carrier i s 5 kHz? (AUC DEC 2011)

24. State the applications of FDM. (AUC MAY 2011)

25. What is meant by frequency translation? (AUC DEC 2011)

26. Compute the bandwidth of the amplitude modulated signal given by s(t)=23[1+0.8

cos(310t)]cos(230000πt) (AUC MAY 2012)

27. What are the causes of linear distortion (AUC MAY 2012)

PART- B

1. Discuss coherent detection of DSB-SC modulated wave with a block diagram of the

detector. (AUC NOV 2006)

2. Draw the filtering scheme for the generation of VSB modulated wave and Explain.

(AUC NOV 2007)

3. Explain the double side band suppressed carrier modulation technique

(AUC NOV 2007)

4. Explain frequency translation. (AUC NOV 2007)

5. Discuss Frequency Division Multiplexing. (AUC NOV 2007)

6. Explain in detail about the balanced modulator with block diagram.

(AUC NOV 2007)

7. Discuss the method of demodulation of DSBSC signal using costas loop.

(AUC MAY 2008)

8. An SSB signal is generated by modulating an 800 KHz carrier by the signal m(t) =

cos2000πt + 2sin1200πt. The amplitude of the carrier is Ac=10. Obtain the

magnitude spectrum of the lower sideband SSB signal. (AUC MAY 2008)

9. With a neat block diagram explain the SSB transmission. (AUC NOV 2008)

10. Explain the operation of a ring modulator. State its advantages. (AUC NOV 2008)



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11. (i)Draw an envelope detector circuit used for demodulation of AM and explain its

operation. (10)

(ii) How SSB can be generated using Weaver’s method? Illustrate with a neat block

diagram. (6) (AUC MAY 2010)

12. (i) Discuss i n detail about frequency translation and frequency division multiplexing

technique with diagrams. (10)

(ii) Compare Amplitude Modulation and Frequency Modulation. (6) (AUC MAY 2010)

13. (i)With the help of a neat diagram, explain the generation of DSB-SC using.Balanced

modulator. (8)

(ii) Write about the coherent detection method in detail for DSB-SC and SSB- SC.

What happens when there is phase mismatch? (8) (AUC DEC 2010)

14. (i) Explain the concept of Frequency Translation. (4)

(ii) With aid of block diagram explain the principle of FDM. (8)

(iii) Illustrate the formation of Basic group and super group. (4) (AUC DEC 2010)

15. With a help of a neat diagram, explain the operation of an envelope detector. Why

does negative peak clipping take place (AUC MAY 2011)

16. (i)Compare the characteristics of DSBFC, DSBSC, SSBFC, SSBSC, VSB schemes.

(ii)Explain the concept of FDM with a suitable block diagram (AUC MAY 2011)

17. With necessary diagrams and expressions explain the generation and demodulation

of AM. (AUC DEC 2011)

18. (i)Compare the various amplitude modulation schemes.(6)

(ii)With neat block diagram, explain the transmitter and receiver section ofFrequency

Division Multiplexing. (10) (AUC DEC 2011)

19. (i)Draw an envelope detector circuit used for demodulation of Am and explain its

operation

(ii)How SSB can be generating using Weaver’s method? Illustrate with a neat block

diagram (AUC MAY 2012)

20. (i)What is frequency division multiplexing? Explain

(ii)Compare various Amplitude modulation systems (AUC MAY 2012)



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UNIT-II ANGLE MODULATION SYSTEMS

PART- A

1. What is frequency deviation in FM? (AUC NOV 2006)

2. What are the applications of phase locked loop? (AUC NOV 2006)

3. What is narrow band FM? (AUC MAY 2006)

4. Determine and draw the instantaneous frequency of a wave having a total phase

angle given by Ф (t) = 2000t + sin 10t (AUC MAY 2006)

5. State Carson’s rule. (AUC NOV 2007)

6. Define phase modulation. (AUC NOV 2007)

7. Mention advantages of angle modulation over amplitude modulation.

(AUC NOV 2008)

8. State the disadvantages of FM. (AUC NOV 2008)

9. When modulating frequency in an FM system is 500 Hz and modulating voltage is

3V, modulation index is 60. Calculate maximum deviation and bandwidth.

(AUC NOV 2008)

10. Draw the phasor diagram, frequency spectrum of narrowband FM.

(AUC MAY 2004) (AUC NOV 2006) (AUC MAY2010)

11. Distinguish between slope detector and Foster Seeley discriminator(AUC MAY 2009)

12. Define modulation index of the FM wave. (AUC MAY 2009)

13. Differentiate between narrowband FM and Wideband FM. (AUC MAY 2009)

14. Obtain the bandwidth of the FM signal

c(t) = 10*cos[2*107*πt + 8 cos(1000*πt)] (AUC MAY 2009)

15. Draw t he block diagram of a method for generating a narrowband FM signal.

(AUC MAY 2010)

16. A carrier wave of frequency 100 MHz i s frequency modulated by a signal 20

sin(200π × 103t). (AUC MAY 2010)

17. Distinguish between narrow band FM and wide band FM (AUC MAY 2011)

18. What is meant by detection? Name the methods for detecting FM signals

(AUC MAY 2011)

19. How is the Narrow band FM converted into wideband FM? (AUC DEC 2011)

20. What are the advantages of Ratio detector? (AUC DEC 2011)

21. Illustrate the relationship between FM and PM, with block diagram. (AUC MAY 2012)

22. What is meant by detection? Name the method for detecting FM signal.

(AUC MAY 2012)



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PART- B

1. (i) Explain any two techniques of demodulation of FM.

(ii) Explain how varactor diode can be used for frequency modulation.

(AUC NOV 2005)

2. Derive the expression for the frequency modulated signal. Explain what is meant by

narrow band FM and wide band FM using expression. (AUC NOV 2006)

3. Discuss the indirect method of generating a wide-band FM signal

(AUC NOV 2006)

4. Draw the circuit diagram of Foster-seeley discriminator and explain its working

(AUC NOV 2006)

5. Explain the direct FM generation using varactor diode and VCO (AUC NOV 2007)

6. Explain in detail about (i) Balanced discriminators (ii) Phase-shift discriminators.

(AUC NOV 2007)

7. Derive the expression for the spectrum of a FM signal with single tone modulation.

(AUC MAY 2009)

8. Give the method of generation of FM signal. (AUC MAY 2009)

9. (i) Using suitable Mathematical analysis show that FM modulation produces infinite

sideband. Also deduce an expression for the frequency modulated output and its

frequency spectrum. (10)

(ii) How can you generate an FM from PM and PM from FM? (6) (AUC MAY 2010)

10. (i) A 20 MHz i s frequency modulated by a sinusoidal signal such that t he maximum

frequency deviation is 100 kHz. Determine the modulation index and approximate

bandwidth of t he FM signal for t he following modulating signal frequencies, (1)1 kHz

(2) 100 kHz and (3) 500 kHz. (8)

(ii) Derive the time domain expressions of FM and PM signals. (8) (AUC MAY 2010)

11. (i)Derive the expression for the single tone frequency modulation and draw its

frequency spectrum

(ii)An angle modulated wave is described by the equation V (t) = 10 cos (2 £ 106¼t

+10 cos 2000¼t). Find (1) Power of the modulated signal (2) Maximum frequency

deviation (3) Bandwidth. (AUC MAY 2011)

12. (i)A 100 kHz carrier is frequency modulated to produce a peak deviation of This FM

signal is passed through a 3 by 3 by 4 frequency.multiplierchain, the output of which is

mixed with an oscillator signal and the difference frequency taken as the new output

Determine the frequency of the oscillator required to produce a 100 kHz FM

output and the peak deviation of the output



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13. (ii)With necessary diagrams explain the operation of slope detector for demodulating

FM signal. (AUC MAY 2011)

14. (i) Define frequency modulation. Draw the FM waveform. Derive an expres-sion for

single tone frequency modulation.(2 + 2 + 6)

(ii) Compare Narrowband and Wideband FM.(6) (AUC DEC 2011)

15. Write about the basic principle of FM detection and explain about radio detector

(AUC DEC 2011)

16. Fig. Shows block diagram of WBFM modulator used to transmit audio signal

containing frequencies in the range 100 Hz to 15kHz. The desired Fm signal at the

transmitter output is to have a carrier frequency of 100 MHz and minimum frequency

deviation deviation of 75 k Hz. Asume the modulation index β=0.2radeian for NBFM.

Find the frequency multiplier values N1,N2 and avlues of acrrier frequency and

frequency deviation at the various points in WBFM modulator. (AUC MAY 2012)

17. Draw the circuit diagram of Foster Seeley discriminator and explain its working with

relevant phasor diagram. (AUC MAY 2012)

Integrator NBFM

Crystal Controlled

Oscillator(9.5MHz)

Crystal Controlled

Oscillator(0.1MHz)

Freq

Multiplier

Mixer

Freq

Multiplier



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UNIT-III NOISE THEORY

PART-A

1. What is the classification of random process? give one example for each

(AUC MAY 2006)

2. Define random process? (AUC NOV 2006)

3. Define noise figure (AUC MAY 2008)

4. What is white noise? (AUC MAY 2008)

5. Define noise equivalent bandwidth (AUC MAY 2008)

6. What is partition noise? (AUC MAY 2008)

7. Draw the auto correlation function and power spectral density of white noise.

(AUC MAY 2008)

8. Define noise factor (AUC NOV 2008)

9. Define noise temperature (AUC MAY 2004)(AUC NOV 2008)

10. Calculate noise figure and equivalent noise temperature for a receiver connected to

an antena whose resistance is 100Ω and equivalent noise resistance is 50Ω?

(AUC NOV 2008)

11. State central limit theorem. (AUC NOV 2008)

12. Give the characteristic of shot noise (AUC MAY 2009)

13. What are the advantages of Gaussian process? (AUC MAY 2009)

14. Define shot noise and thermal noise? (AUC MAY 2010)(AUC MAY 2009)

15. Determine the equivalent noise temperature for a noise figure of 10 dB

(AUC MAY 2010)

16. When i s a random process called deterministic? (AUC MAY 2010)

17. A receiver conected to an antenaof resistance of 50Ω has an equivalent noise

resistance of 30Ω. Find the receiver noise figure. (AUC MAY 2010)

18. Define a random variable. Specify the sample space and the random variable for a

coin tossing experiment. (AUC DEC 2010)

What i s white noise? Give its characteristics. (AUC DEC 2010)

19. Write the Rayleigh and Rician probability density functions (AUC MAY 2011)

20. What is white noise? State its power density (AUC MAY 2011)

21. When i s a random process called deterministic? (AUC DEC 2011)

22. Two resistors of 20 KΩ, 50 KΩ are at room temperature (290 K). For a bandwidth

of 100 KHz, calculate the thermal noise voltage generated by the two resistors in

series



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23. Define random variable. Specify the sample space and the random variable for a coin

tossing experiment (AUC MAY 2012)

24. Give the definition of the noise equivalent temperature (AUC MAY 2012)

PART-B

1. Write notes on noise temperature and noise figure (AUC MAY2004)

2. Explain the following terms(i)Random variable (ii)Gaussian process(iii) Shot noise

(iv) Noise temperature (AUC NOV 2006)

3. Explain the following terms (i)Thermal noise(ii)White noise(ii)Narrow band noise

a. (iv) Random noise (AUC NOV 2006)

4. Explain concept of noise equivalent bandwidth (AUC NOV 2007)

5. Discuss the type’s causes and effects of various forms of noise created within a

receiver? (AUC NOV 2008)

6. A stationary Gaussian process X (t) with zero mean and power spectral density Sx(f)

is applied to a linear filter whose impulses response h(t) is shown in figure. a sample

Y is taken of the random process at the filter output at the time T.

i)Determine the mean and variance of Y.

ii) What is the probability density function of Y? (AUC NOV 2008)

7. Derive the noise figure of an receiver having input impedance Rt, output impedance

RL and overall voltage gain A? (AUC NOV 2008)(AUC MAY 2009)

8. Explain in detail about the white noise and filtered noise (AUC NOV 2008)

9. Explain the following terms

i. Statistical average, correlation, covariance and ergodicity?

ii. Discuss the properties of Gaussian process? (AUC MAY 2008)

10. i)Determine the overall noise figure of a three stage cascade amplifier; each stage

having a power gain of 10dB and noise figure of 6dB?

ii) Discuss the properties of narrow band noise. (AUC MAY 2008)

11. What is thermal noise in communication? What are the different types of

noise?Explain

(AUC MAY 2009)

12. i)Give a random process, X (t) = A cos(ωt+ θ), where Aand ω a re constants and θ i s

a uniform random variable. Show that X (t) is ergodic in both mean and

autocorrelation. (8)



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ii) Write a short note on shot noise and also explain about power spectral density of

shot noise. (8) (AUC MAY 2010)

13. Write t he details about narrow band noise and t he properties of quadrature

components of narrowband noise. (16) (AUC MAY 2010)

14. (i) List the different types of random process and give the definitions. (10)

(ii) Write short notes on shot noise. (6) (AUC DEC 2010)

15. (i) A mixer stage has a noise figure of 20 dB and this i s preceded by an amplifier

that has a noise figure of 9 dB and an available power gain of 15 dB. Calculate the

overall noise figure referred to the input. (8)

(ii) A receiver has a noise figure of 12 dB and it is fed by a low noise amplifierthat has

a gain of 50 dB and a noise temperature of 90 K. Calculate the noise temperature of

the receiver and the overall noise temperature of the receiving system. Take room

temperature as 290 K. (8) (AUC DEC 2010)

16. State and prove four properties of Gaussian process (AUC MAY 2011)

17. (i)Derive the representation of narrow band noise in terms of envelop and phase

component and list out its properties

(ii)Consider two amplifiers are connected in cascade. First stage amplifier has gain

and noise figure as 10 dB and 2 dB. Second stage has noise figure of 3 dB.

(AUC MAY 2011)

18. (ii)State any 5 properties of autocorrelation function(10)

(ii)When is a random process said to be strict stationary (SSS), wide sense stationary

(WSS) and ergodicprocess(6) (AUC DEC 2011)

19. (i)Explain Narrowband Noise. Show that a narrow band noise n(t) can be represented in

terms of its in phase and qudrature phase components

(ii)Thermal noise from a measured as 4*10-17 W at a temperature of 200 C for a given

bandwidth. What will be the Noise power when temperature is changed to 500

(AUC DEC 2011)

20. (i)List the different type of random process and give the definitions(10)

(ii)Write short notes on shot noise (6) (AUC MAY 2012)

21. (i)Write the definition, power spectral density and autocorrelation function for white noise

and narrow band noise(filtered white noise)(10)

(ii)What causes thermal noise in a materiala? Write the expression for RMS values of

the noise. (AUC MAY 2012)



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UNIT-IV PERFORMANCE OF CW MODULATION SYSTEMS

PART-A

1. What are the advantages of the super heterodyne receiver over TRF receiver?

(AUC MAY 2004)

2. What is FM threshold effect? (AUC MAY 2004)

3. What is the NiSi

NS

/

0/0for AM (with envelope detection) with small noise case.

(AUC NOV 2005)

4. What is meant by figure of merit of a receiver? (AUC NOV 2006)

5. What are called extended threshold demodulators? (AUC NOV 2006)

6. What is the purpose of pre-emphasis and de-emphasis in FM?

(AUC NOV 2006, AUC MAY 2007, AUC NOV 2007)

7. What is threshold effect with respect to noise? (AUC MAY 2007)

8. What do you understand by ‘capture effect’ in FM? (AUC MAY 2008)

9. Compare the noise performance of AM and FM systems. (AUC MAY 2008)

10. What do you understand by FM stereo multiplexing? (AUC MAY 2009)

11. Compare the noise performance of AM and FM systems. (AUC MAY 2009)

12. What is meant by FM threshold effect? (AUC MAY 2010)

13. Draw the circuit diagram of pre-emphasis filter (AUC MAY 2010)

14. What are the characteristics of super heterodyne receivers? (AUC MAY 2010)

15. What are the methods to improve FM threshold reduction? (AUC MAY 2010)

16. Define threshold effect in AM receiver. (AUC DEC 2010)

17. Define pre-emphasis and de-emphasis. (AUC DEC 2010)

18. Compare the noise performance of DSBSC receiver using coherent detection

with AM (AUC MAY 2011)

19. What are the methods to improve FM threshold reduction? (AUC MAY 2011)

20. What is FM Threshold effect? (AUC DEC 2011)

21. Define threshold effect in AM receiver. (AUC DEC 2011)

22. Determine the range of tuning of a local oscillator of a super Heterodyne receiver

when fLO>fc. The broadcast frequency range is 540Hz to 1600 Hz. Assume

Fif=445kHz

(AUC MAY 2012)

23. What is capture effect in FM? (AUC MAY 2012)



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PART-B

1. (i) Explain the noise in AM receiver using its noisy model block diagram.

(ii) What are pre-emphasis and de-emphasis in FM? Draw suitable circuits and

explain.

(AUC MAY 2007, AUC MAY 2004, AUC NOV 2005, AUC NOV2006, AUC MAY 2008)

2. (i) Explain the capture effect and FM threshold effect.

(ii) Draw the block diagram of FM demodulator and explain the effect of noise in

detail and compare the performance of AM and FM in the presence of noise.

(AUC NOV 2006)

3. Explain the working of super heterodyne receiver. (AUC MAY 2006)

4. Compare the noise performance of AM and FM systems.

(AUC NOV2005, AUC MAY2007)

5. (i) Derive the output SNR for envelope detection.

(ii) Explain the FM receiver with block diagram. (AUC NOV 2007)

6. Write a note on the following: (i)FM threshold Effect

(ii) FM threshold reduction. (AUC MAY 2008)

7. Why pre-emphasis is used in FM system? Sketch a typical pre-emphasis circuit.

(AUC MAY 2008)

8. State central limit theorem. (AUC NOV 2008)

9. (i) Draw the model of DSB/SC receiver that using coherent detection and derive its

figure merit.

(ii) Discuss about the noise performance of an FM receiver to evaluate its figure of

merit. (AUC NOV 2008)

10. Derive the expression for the Power spectral density at the output of a FM

discriminator when the received signal is corrupted by additive white Gaussian Noise.

(AUC MAY 2009)

11. Derive a n expression for SNR at input (SNRc) and output of (SNRo) of a coherent

detector. (16) (AUC MAY 2010)

12. (i) Explain pre-emphasis and De-emphasis i n detail. (10)

(ii) Compare the performances of AM and FM systems. (6) (AUC MAY 2010)

13. Derive the expression for figure of merit of an AM receiver using envelope

Detection. What do you infer from the expression? (16) (AUC DEC 2010)

14. Define and explain FM Threshold effect. With suitable diagram, explain

threshold reduction by FMFB demodulator. (16) (AUC DEC 2010)



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15. (i)Sketch the block diagram of DSB-SC/AM system and derive the figure of merits

(ii)Using super heterodyneprinciple, drawthe block diagram of AM radio receiver and

briefly explain it (AUC MAY 2011)

16. (i)Explain pre-emphasis and De-emphasis in detail.

(ii)Compare the performances of AM and FM systems(AUC MAY 2011)

Obtain the expression for figure of merit of DSB-SC receiver using coherent

detection. (AUC DEC 2011)

17. (i)Derive the figure of merit for FM Receiver.(10)

(ii)What is the necessity of pre-emphasis and de-emphasis used in FM System?

Explain pre-emphasis and de-emphasis with neat circuit.(6) (AUC DEC 2011)

18. Sketch the block diagram of DSB-SC/AM system and derive the figure of merit.

(AUC MAY 2012)

19. Using super heterodyne principle, draw the block diagram of AM radio

20. Discuss the effects of noise on the carrier in FM receiver with suitable mathematical

derivation. (AUC MAY 2012)



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UNIT-V INFORMATION THEORY

PART-A

1. What is binary symmetric chanel (AUC DEC 2006)

2. What is discrete chanel capacity (AUC DEC 2006)

3. Define information rate? (AUC DEC 2007)

4. Define entropy? (AUC DEC 2007)

5. Define mutual information? (AUC MAY 2008)

6. Find the entropy

Symbol S0 S1 S2 S3 S4

probability 0.4 0.3 0.1 0.1 0.1

(AUC DEC 2008)

7. State Shanon first theorem? (AUC DEC 2008)

8. State chanel capacity theorem. (AUC MAY2008)

9. Define entropy for a discrete memory less source. (AUC MAY 2007)

10. State chanel coding theorem. (AUC MAY 2007)

11. What is chanel capacity of binary synchronous chanel with error probability of 0.2?

(AUC DEC 2007)

12. Calculate the entropy of the source with a symbol set containing 64symbols each

with a probability pi =1/64? (AUC APR 2008)

13. Compare Shanon and Huffman coding. (AUC MAY 2009)

14. A discrete memoryless source with source alphabet S= S0, S1, S2 with respective

probabilities P=1/4,1/4,1/2. Find the entropy. (AUC MAY 2010)

15. Determine differential entropy. . (AUC MAY 2010)

16. Define entropy function.

17. Define Rate Bandwidth and Bandwidth efficiency.

18. A source generates 3 messages with probability 0.5, 0.25, 0.25. Calculate source

entropy. (AUC DEC 2010)

19. Define Rate Bandwidth and Bandwidth efficiency. (AUC DEC 2010)

20. Define entropy function. (AUC MAY 2011)

21. Differentiate between lossless and lossy coding (AUC MAY 2011)

22. State Shannon’s channel capacity theorem, for a power and band limited channel. (AUC DEC 2011)

23. Calculate the Entropy of the Source with symbol probabilities 0.6, 0.3 and 0.1.

(AUC DEC 2011)

24. A source generate three message with probability 0.5,0.25,0.25. calculate H(x)

(AUC MAY 2012)

25. State the advantages of Lempi=Ziv coding (AUC MAY 2012)



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PART-B

1. Five symbols of the alphabet of a discrete memory less source and their probabilities

are given below:[s] = [so , s1 , s2 , s3 , s4]

[P(s)] = [0.4 ,0.2 , 0.2 ,0.1 , 0.1]

Code the symbols using Huffman coding. (AUC NOV 2006)

2. (i) Define Mutual information. Find the relation between the mutual information and

the joint entropy of the chanel input and chanel output.

(ii) What are the implications of information capacity theorem? (AUC NOV 2006)

3. (i) Discuss the source coding theorem.

(ii) Give the advantage and disadvantage of chanel coding in detail.

(iii) Discuss the data compaction. (AUC MAY 2007)

4. (i) Write short notes on differential entropy.

(ii) Derive the chanelcapacity theorem.

(iii)Discuss the implication of the information capacity theorem. (AUC MAY2007)

5. A discrete memory less chanel has the following alphabet with probability of

occurrence.

Symbol S0 S1 S2 S3 S4 S5 S6

Probability 0.125 0.0625 0.25 0.0625 0.125 0.125 0.25

Generate the Huffman coding. Find average Coded Length, entropy and η.

` (AUC NOV 2007)

6. (i)Derive the expression for chanel capacity of a binary symmetric chanel.

(ii) Encode the following source using Huffman Coding.

X = x1, x2 , x3 , x4 , x5

P(X) = 0.2, 0.02 , 0.1 , 0.38 , 0.3 (AUC MAY 2006)

7. Derive the expression for chanel capacity of a continuous chanel. Find also the

expression for chanel capacity of a continuous chanel of infinite bandwidth comment

on the results. (AUC MAY 2006)



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8. Consider a sequence of letters of English alphabet with their probabilities of

occurrence as given.

Letter A I L M N O P Y

Probability 0.1 0.1 0.2 0.1 0.1 0.2 0.1 0.1

Compute two different Huffman codes for this alphabet. Also for each of the two codes,

find the average code-word length and variance of average code-word length over

ensemble of letters. (AUC NOV 2008)

9. (i) Consider a discrete memory less chanel with input alphabet X, output alphabet Y

and transition probabilities p(Yk / Xj ). Find the mutual information of chanel to obtain

the chanel capacity. Also find the chanel capacity of binary symmetricchanel.

(ii) Elaborate the chanel coding theorem with an example. (AUC NOV 2008)

10. Discuss the various technique used for compression of information

(AUC MAY 2009)

I. Define differential entropy.

II. Define Mutual information.

III. What is the relation between mutual information and chanel capacity?

IV. Give the (Shanon- Hartley) information capacity theorem and

Discuss the implication of the same in detail. (AUC MAY 2009)

11. (i) Find the code words for five symbols of t he alphabet of a discrete memoryless

source with probability 0.4, 0.2, 0.2, 0.1, 0.1, using Huffman coding and determine

the source entropy and average code word length. (10)

(ii) Discuss the source coding theorem. (6) (AUC MAY 2010)

12. (i) Derive t hechanel capacity of a continuous band limited white Gaussian noise

chanel. (10)

(ii) Discuss about rate distortion theory. (6)(AUC MAY 2010)

13. (i) An Analog signal i s band limited to `B' Hz and sampled at Nyquist rate. The

sampled signals are quantized into 4 levels. Each level represents

one message. The probability of occurrence of the four messages are

p1=p3=1/8; p2=p4=3/8. Find out information rate of the source. (6)

(ii) Five source messages are probable to appear as m1 = 0:4, m2 = 0:15,

m3 = 0:15, m4 = 0:15, m5 = 0:15. Find coding efficiency for (1) Shannon-

Fano coding, (2) Huffman coding.

(10) (AUC DEC 2010)



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14. (i) Derive the chanel capacity for Binary Symmetric chanel.(6)

(ii) Derive the chanel capacity for band limited, power limited Gaussian

Chanel. (10) (AUC DEC 2010)

15. Using Huffman code I, encode the following symbols.S = [0.3, 0.2, 0.25, 0.12, 0.05,

0.08,]Calculate average code length, entropy of the source, code efficiency,

redundancy (AUC MAY 2011)

16. i)State and prove the properties of mutual information

ii)The channel transition matrix [0.9 0.1 0.2 0.8 ]. Draw the channel diagram and

determine the probabilities associated with output assuming equipropable inputs.

(AUC MAY 2011)

17. Justify the need for an efficient source encoding process in order to increase the

average transmitted information per bit, if the source emitted symbol are not equally

likely with example .consider a discrete memoryless source for your justification

18. Eight possible messages m1,m2,m3,m4,m5,m6,m7 and m8 from a source and their

P(m1)=0.5,P(m2)=0.15,P(m3)=0.15,P(m4)=0.08,P(m5)=0.08,P(m6)=0.02,P(m7)=0.0

1,P(m8)=0.01.Construct the Shannon fano coding for each of these message in

order to increase the average information per bit. Find the coding efficiency.

(AUC DEC 2011)

19. State and explain Shannon theorem on channel capacity(12)

Define Mutual information. State any two propertites(4) (AUC DEC 2011)

20. A Database Management System (DMS) has following alphabet with probability of

occurrence as shown below

Symbol S0 S1 S2 S3 S4 S5 S6

probability 0.125 0.0625 0.25 0.06252 0.125 0.125 0.25

(AUC MAY 2012)

21. Derive Shannon-Hartley theorem for the channel capacity of a continous channel

having an average limitation and perturbed by an additive band limited white

Gaussian noise. Explain the bandwidth signal to noise radio trade off for this theorem

(AUC MAY 2012)


ec2252 communication theory

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