Wireless Communication (EC-802 (B)) - Important Questions

Discuss the history and evolution of wireless communication from early systems to 1G-5G and the technical and economic requirements driving development

Explain the different types of wireless services and their technical, economic and social requirements and impact

Explain the key technical challenges in wireless communications, including effects of multipath propagation and user mobility.

Explain the phenomenon of multipath propagation and how it leads to noise and interference-limited systems.

Differentiate reflection, diffraction and scattering as propagation mechanisms and explain wave guiding and the effect of rough surfaces on scattering.

Explain spectrum limitations in wireless communication and their impact on system design.

Explain scattering of waves on rough surfaces using Kirchhoff theory and perturbation theory.

Define reflection and transmission in wireless communication.

Explain the time-variant two-path channel model (and differentiate time-invariant vs time-variant with mathematical representation).

Derive / discuss the Doppler spectrum and its relation to mobile velocity and temporal fading.

Define/explain the WSSUS model, its diagram, condensed parameters, and importance for system-theoretic description of wireless channels.

What are Ultra-Wideband (UWB) channels, their characteristics, and how do they differ from conventional narrowband directional channel descriptions?

Explain the concept of coherence bandwidth and its relation to delay spread in wireless channels.

Derive the expression for Doppler shift in a mobile wireless channel and effect of velocity.

Describe small-scale vs large-scale fading and impact of Doppler shift on communication.

Derive the expression for delay spread and coherence bandwidth and explain the effect of delay spread on system performance.

Derive the amplitude and phase distribution for small-scale fading with a dominant LOS component.

Characterize a wireless channel as a deterministic linear time-variant system.

Classify causes of delay dispersion in directional channels and their remedies.

Write short notes on Antenna for Mobile Stations and TDMA and CDMA Systems (choice-based short notes).

Explain / compare the narrowband, wideband, and directional channel models, their architecture, implementation and applications

What is channel sounding? Explain the time-domain channel sounding measurement technique with block diagram and its limitations.

Describe the frequency-domain channel sounding method and compare its advantages and disadvantages over time-domain measurement techniques.

Explain the process of channel sounding and describe the different measurement methods used for characterizing wireless channels.

Derive the expression for Rayleigh (far-field) distance in terms of antenna dimension and compute it for a square antenna with 20 dB gain.

Discuss wideband channel models

Discuss ray tracing and efficiency considerations for deterministic channel modeling

Explain narrowband, wideband and directional models and discuss deterministic channel modeling methods

Sketch and explain the block diagram / structure of a wireless communication link / transceiver and its characteristics, including the role and impact of modulation and demodulation.

Compare the performance of BPSK, QPSK and QAM in terms of spectral efficiency, power efficiency and suitability for fading channels.

Evaluate and compare the error probability performance of digital modulation schemes when operating in flat-fading channels versus AWGN channels.

Explain the impact of delay and frequency-dispersive fading on signal reception. How does it affect the error probability?

Compare the spectral efficiency of MSK and QPSK.

Discuss the AWGN channel model and the error probability in AWGN channels.

Define diversity in wireless communication, differentiate between microdiversity and macrodiversity (including simulcast), and explain how diversity improves reliability and signal reception.

What is transmit diversity and explain Alamouti's space-time block coding (STBC) scheme and its significance in MIMO systems?

Give a brief introduction to / explain diversity and microdiversity in a wireless system.

Compare blind equalization and decision-directed equalization and state when blind equalization is preferred.

Write short notes on Viterbi detector, WSSUS model, and antennas for mobile stations.

Explain the fractional spaced equalizer.

Explain importance of equalizers in wireless devices and classify / compare equalizer structures with examples.

Write short notes on fading channels, blind equalizers, Viterbi detector, fractional spaced equalizer, and Doppler spectra.