This document can help the students, who want to pursue their carrier in the wireless industry for cracking the interview.

1. 100 Interview Question in Wireless Communication
Dr. Varun Kumar
1. What do you mean favourable propagation?
2. What is TDD and FDD ? Define its slot structure.
3. What are the challenges of TDD ?
4. Can we achieve the channel reciprocity using frequency division duplexing ?
5. What is coherent and non-coherent detection ?
6. Why FDD is not suitable for massive MIMO communication ?
7. Can massive MIMO nullify the effect of inter-user interference ?
8. Difference between Rayleigh, Racian and Nakagami fading.
9. Difference between time flat and time selective, frequency-flat and frequency-
selective, and doubly selective channel.
10. What is coherence time and coherence bandwidth ?
11. What is equalizer and how it improves the signal quality ?
12. What is the significance of auto-correlation ?
13. What is the difference between large and small-scale effect?
14. Difference between FDM, OFDM, and OFDMA.
15. What do you mean by interleaver in communication system?
16. What is the difference between multiplexing gain and diversity gain.
17. What is water-filling algorithm ?
18. What do you mean by transmit diversity and receive diversity ?
19. What are the functions of precoder and decoder ?
20. What is the usage of circular convolution and correlation in communication
system ?
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2. 21. What is the usage of I-FFT block in OFDM receiver ?
22. What do you mean by channel correlation and its drawback on communication
system ?
23. Difference between random variable and random process.
24. What is the difference among stationary, non-stationary, wide sense stationary
and cyclo-stationary processes ?
25. What is the significance of linear phase ?
26. What do you mean by linear and non-linear distortion ? What is the cause
for arising these type of distortion ?
27. What do you mean by orthogonal vector space and orthogonal signal space ?
28. What is significance of negative frequency ?
29. What do you mean by group delay and phase delay ?
30. What is uniform and non-uniform quantization ?
31. What do you mean by source coding, channel coding, and line coding ?
32. What is the difference between regenerative repeaters and amplifier ?
33. What is the Nyquist’s criterion for zero ISI ?
34. What is zero-forcing equalizer ?
35. What is the difference between independent, un-correlated, and orthogonal ?
36. What is central limit theorem ?
37. What do you mean by band pass random process ?
38. What are the important properties of Gaussian random process ?
39. What do you mean by colored channel noise ?
40. What is non-coherent detector ?
41. Difference between multiplexing and multiple access ?
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3. 42. What is near-far problem in CDMA ?
43. What is maximum likelihood receiver ?
44. What is minimum mean square error (MMSE) receiver ?
45. What is channel quality indicator (CQI) ?
46. What is antialiasing filter and matched filter ?
47. What is the use of cyclic prefix in OFDM communication system ?
48. What do you mean by a memory-less channel and channel having memory ?
49. Explain channel capacity in terms of mutual information.
50. What will be the channel capacity when transmitter knows the CSI and with-
out knowing the CSI ?
51. In which mode OFDMA and SC-FDMA is used and why ?
52. What is Alamouti’s code and what is its usage ?
53. What is the antenna correlation and what is its remedy for getting uncorre-
lated channel ?
54. Difference between MIMO and massive MIMO.
55. What do you mean by pilot contamination ?
56. In QAM modulation, what is the significance of quadrature or why quadrature
term is used ?
57. What do you mean by frequency reuse ratio and how it works ?
58. What is the difference between MLE and MAP ?
59. What is frequency hopping ?
60. What is the difference between microwave and mm-Wave ? Why its nomen-
clature is like this ?
61. What is carrier frequency offset (CFO) and what is its adverse effect on com-
munication system ?
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4. 62. What is the meaning of cross power spectral density ?
63. Advantage of digital communication over analog communication.
64. What are the practical issues in signal sampling and signal reconstruction ?
65. What is superheterodyne receiver and how it works ?
66. Basic difference between 4G and 5G.
67. Difference between AF, DF and CF relaying in communication system.
68. If transmitter and receiver units are in static mode then can we diversity with
greater extent ?
69. What are different types of band that is used for the communication.
70. What is 5G-NR ?
71. What is URLLC in 5G ?
72. What is the significance of complex base-band signal ?
73. What is the practical difficulty with ideal low pass filter ?
74. What is the difference between IIR and FIR filter ?
75. What is envelope detector and product modulator ?
76. What is power delay profile and RMS delay spread ?
77. What is the difference between analog and digital beamforming ?
78. What are the difference among QPSK, O-QPSK and π
4 -QPSK ?
79. What is singular value decomposition and where it is used in communication
system ?
80. What is the difference between data and signal ?
81. What is the Fourier transform of an auto-correlation function.
82. What is NOMA ?
83. What is the meaning of full duplex communication ?
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5. 84. What are the basic steps for communicating between mobile device (Ex- jio
and airtel) ?
85. What are the important areas of 5G research ?
86. What will be the impact of base station height in communication system ?
87. What is inter-symbol interference (ISI) and inter-carrier interference (ICI) ?
88. What is MAN, WAN, and RAN in communication network ?
89. What is 802.11b/g/n ?
90. Difference between Fourier transform and Fourier series.
91. Difference between PM and FM and what is kp and kf ?
92. What is the difference between SSB and DSB modulation ? What are the
ways for extracting modulated signal ?
93. What are the methods for making frequency multiplier ?
94. What is the significance of marginal, conditional and joint entropy in commu-
nication system ?
95. What is linear block code and cyclic code ?
96. What is the major role of L2 layer in data communication ?
97. What is the application of network layer ?
98. How can you link with data communication with the analog and digital com-
munication ?
99. What is syndrome in channel coding ?
100. What is low density parity check (LDPC) codes and what is its usage in
communication ?
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