EC-802-B Wireless Communications - May 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aWhat is the history behind the evolution of wireless communication?
   How to answer

   • Brief timeline of wireless development from early radio to cellular generations
   • Key milestones: Marconi, cellular concept, 1G to 5G evolution
   • Role of standards and technologies in evolution
2. 7 Marks
   bUsing Kirchhoff theory and perturbation theory explain scattering of wave on rough surface.
   How to answer

   • Statement of Kirchhoff theory for scattering from rough surface
   • Statement of perturbation theory approximation
   • Application to wave scattering and resulting scattering coefficients
3. 14 Marks
   Derive the expression of Rayleigh distance in terms of antenna dimension. Also compute the Rayleigh distance of a square antenna with 20 dB gain.
   How to answer

   • Definition of Rayleigh / Fraunhofer distance $d = 2D^2/\lambda$
   • Derivation from phase error criterion across antenna aperture
   • Computation for square antenna with 20 dB gain to obtain dimension and distance
4. 7 Marks
   aExplain the time variant two path model for wireless channel.
   How to answer

   • Description of two-ray / two-path time-variant channel
   • Channel impulse response with direct and delayed path
   • Effect of mobility and time-varying phase / Doppler
5. 7 Marks
   bGive a derivation of the amplitude and phase distribution for a small scale fading with a dominant component.
   How to answer

   • Signal model with dominant LOS plus scattered components
   • Derivation steps leading to Rician amplitude distribution
   • Phase distribution expression for small-scale fading
6. 7 Marks
   aDiscuss about the Doppler Spectra in wireless system.
   How to answer

   • Origin of Doppler shift due to mobility
   • Doppler power spectrum concept e.g. Clarke/Jakes spectrum
   • Impact on fading rate and channel variation
7. 7 Marks
   bCharacterize a wireless channel as deterministic linear time variant system.
   How to answer

   • Linear time-variant system representation with impulse response $h(\tau,t)$
   • Input-output relation via convolution
   • Deterministic characterization using delay-Doppler functions
8. 7 Marks
   aDiscuss about the wide band models.
   How to answer

   • Definition of wideband vs narrowband in terms of delay spread
   • Wideband channel models and tapped-delay-line representation
   • Parameters: delay spread, coherence bandwidth
9. 7 Marks
   bDiscuss about Ray tracing and efficiency consideration for the deterministic channel modeling method.
   How to answer

   • Principle of ray tracing using geometrical optics
   • Steps for deterministic channel modeling
   • Efficiency considerations and computational complexity
10. 14 Marks
    Compare the spectral efficiency of MSK and QPSK.
    How to answer

    • Power spectral density and bandwidth of MSK
    • Power spectral density and bandwidth of QPSK
    • Comparison of spectral efficiency in bits/s/Hz
11. 7 Marks
    aExplain about Micro diversity in wireless system.
    How to answer

    • Concept of micro-diversity to combat small-scale fading
    • Techniques: space, polarization, angle diversity at small scale
    • Combining methods and performance benefit
12. 7 Marks
    bExplain about the fractional spaced equalizer.
    How to answer

    • Structure of fractionally spaced equalizer with tap spacing < symbol period
    • Advantage over symbol-spaced equalizer regarding timing sensitivity
    • Applications in wireless receivers
13. 14 Marks
    Write short notes on any two of the following:

    1. a)Viterbi detector
    2. b)WSSUS model
    3. c)Antennas for mobile stations
    How to answer

    • Key principle and operation of each selected topic
    • Relevant block diagram / mathematical model
    • Applications and advantages in wireless communications