Exam Details

Subject digital communications
Paper
Exam / Course b.tech
Department
Organization Institute Of Aeronautical Engineering
Position
Exam Date January, 2019
City, State telangana, hyderabad


Question Paper

Hall Ticket No Question Paper Code: AEC009
INSTITUTE OF AERONAUTICAL ENGINEERING
(Autonomous)
Four Year B.Tech V Semester End Examinations (Supplementary) January, 2019
Regulation: IARE R16
DIGITAL COMMUNICATIONS
Time: 3 Hours Max Marks: 70
Answer ONE Question from each Unit
All Questions Carry Equal Marks
All parts of the question must be answered in one place only
UNIT I
1. State and prove sampling theorem and explain various types of sampling techniques.
Determine the processing gain of a DPCM system with a first order predictor, if the message
signal has a normalized auto-correlation function of 0.8 for a lag of one period, assuming that
the predictor is designed to minimize the mean square value of the prediction error.
2. Explain PCM modulation and demodulation system with neat sketches. Describe the quantization
noise in PCM.
Find the maximum amplitude of a 1 KHz sinusoidal signal input to a delta modulator that will
prevent slope overload, when the sampling rate is 10,000 samples/sec and the step size is
0.1
UNIT II
3. Explain binary PSK and QPSK with corresponding equations and constellation diagrams.
For the signals, the given bit rate is 10Kbps. Estimate the bandwidth for Amplitude Shift Keying
and Frequency Shift Keying signals.

4. Explain the Non-coherent detection of FSK modulation scheme.
The bit stream 11011100101 is to be transmitted using DPSK. Determine the encoded sequence
and the transmitted phase sequence.
UNIT III
5. Describe the scrambling coding scheme HDB3 and Sketch the signal corresponding to the bit
sequence "01100000000100001100" using rectangular pulses.
Define roll off factor and describe the Nyquist bandwidth requirement of raised cosine filter for
distortion less transmission.
6. What is pulse shaping? Why it is useful in baseband transmission? Explain in detail.
Draw and explain the block diagram of modified duo-binary signaling scheme consider the binary
sequence bk= "01001101" applied to the input of a precoded modified duo-binary sequence.
Determine the sequence ak at the pre-coder output.
Page 1 of 2
UNIT IV
7. Calculate the Conditional entropy, mutual information and channel capacity using channel matrix
for a noise free channel.
Illustrate the principle of Frequency hopped spread spectrum. What is the minimum number
of bits in a PN sequence if we use FHSS with a channel bandwidth of B KHz and Bss=100
KHz?
8. Describe Code Division Multiple Access(CDMA) in detail.
Apply Shannon fano coding for the 5 messages with probabilities 0.4, 0.15, 0.15, 0.15, 0.15 and
find the coding efficiency.
UNIT V
9. Define the following terms
Code word
Block length
Code rate
Channel data rate
Code vector
Hamming distance
Minimum distance
Determine the generator polynomial for A cyclic code and find the code vector for
the following data vector 1010, 1111 and 1000.
10. Explain how generator and parity matrices are obtained for cyclic codes with an example.
Decode the given sequence 11 01 01 10 01 of a convolutional code with a code rate of and
constraint length using viterbi decoding algorithm.
Page 2 of 2


Other Question Papers

Subjects

  • ac machines
  • advanced databases
  • aircraft materials and production
  • aircraft performance
  • aircraft propulsion
  • aircraft systems and controls
  • analog communications
  • analysis of aircraft production
  • antennas and propagation
  • applied physics
  • applied thermodynamics
  • basic electrical and electronics engineering
  • basic electrical engineering
  • building materials construction and planning
  • business economics and financial analysis
  • compiler design
  • complex analysis and probability distribution
  • computational mathematics and integral calculus
  • computer networks
  • computer organization
  • computer organization and architecture
  • computer programming
  • concrete technology
  • control systems
  • data structures
  • database management systems
  • dc machines and transformers
  • design and analysis of algorithms
  • design of machine members
  • digital and pulse circuits
  • digital communications
  • digital ic applications using vhdl
  • digital logic design
  • digital system design
  • disaster management
  • disaster management and mitigation
  • discrete mathematical structures
  • dynamics of machinery
  • electrical circuits
  • electrical measurements and instrumentation
  • electrical technology
  • electromagnetic field theory
  • electromagnetic theory and transmission lines
  • electronic circuit analysis
  • electronic devices and circuits
  • elements of mechanical engineering
  • engineering chemistry
  • engineering drawing
  • engineering geology
  • engineering mechanics
  • engineering physics
  • english
  • english for communication
  • environmental studies
  • finite element methods
  • fluid mechanics
  • fluid mechanics and hydraulics
  • fundamental of electrical and electronics engineering
  • fundamental of electrical engineering
  • gender sensitivity
  • geotechnical engineering
  • heat transfer
  • high speed aerodynamics
  • hydraulics and hydraulic machinery
  • image processing
  • industrial automation and control
  • instrumentation and control systems
  • integrated circuits applications
  • introduction to aerospace engineering
  • kinematics of machinery
  • linear algebra and calculus
  • linear algebra and ordinary differential equations
  • low speed aerodynamics
  • machine tools and metrology
  • mathematical transform techniques
  • mathematical transforms techniques
  • mechanics of fluids and hydraulic machines
  • mechanics of solids
  • mechanism and machine design
  • metallurgy and material science
  • microprocessor and interfacing
  • modern physics
  • network analysis
  • object oriented analysis and design
  • object oriented programming through java
  • operating systems
  • optimization techniques
  • power electronics
  • power generation systems
  • probability and statistics
  • probability theory and stochastic processes
  • production technology
  • programming for problem solving
  • pulse and digital circuits
  • reinforced concrete structures design and drawing
  • software engineering
  • strength of materials - i
  • strength of materials - ii
  • structural analysis
  • surveying
  • theory of computation
  • theory of structures
  • thermal engineering
  • thermo dynamics
  • thermodynamics
  • tool design
  • transmission and distribution systems
  • unconventional machining processes
  • waves and optics
  • web technologies