This set of Wireless & Mobile Communications Multiple Choice Questions & Answers (MCQs) focuses on “Types of Small- Scale Fading”.
1. Which of the following is not a channel parameter?
a) Bandwidth
b) Coherence time
c) Rms delay spread
d) Doppler spread
View Answer
Explanation: Channel parameters are coherence bandwidth, rms delay spread and Doppler spread. Signal parameters are bandwidth and symbol period. Different types of fading occur depending on the relation between channel and signal parameters.
2. ______ leads to time dispersion and frequency selective fading.
a) Doppler spread
b) Multipath delay spread
c) Time dispersive parameters
d) Frequency delay spread
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Explanation: Multipath delay spread leads to time dispersion and frequency selective fading. Doppler spread leads to frequency dispersion and time selective fading. These two propagation mechanism are independent of each other.
3. Which of the following s not a characteristic of flat fading?
a) Mobile radio channel has constant gain
b) Linear phase response
c) Non linear phase response
d) Bandwidth is greater than the bandwidth of transmitted signal
View Answer
Explanation: The received signal will undergo flat fading if mobile radio channel has a constant gain and linear phase response over a bandwidth which is greater than the bandwidth of transmitted signal. It is the most common type of fading.
4. Spectral characteristics of the channel changes with time in flat fading.
a) True
b) False
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Explanation: In flat fading, the multipath structure of the channel is such that spectral characteristics of the transmitted signal are preserved at the receiver. But, the strength of the received signal changes with time due to fluctuations in the gain of channel caused by multipath.
5. Flat fading channel is also known as _______________
a) Amplitude varying channel
b) Wideband channel
c) Phase varying channel
d) Frequency varying channel
View Answer
Explanation: Flat fading channel is also known as amplitude varying channel. They are also sometimes referred to as narrowband channel. In flat fading channel, the bandwidth of the applied signal is narrow as compared to the channel flat fading bandwidth.
6. In a frequency selective fading, mobile radio channel possess a constant gain and a linear phase over bandwidth smaller than bandwidth of transmitted signal.
a) True
b) False
View Answer
Explanation: If the channel possesses a constant gain and linear phase response over a bandwidth that is smaller than the bandwidth of transmitted signal, then the channel creates frequency selective fading on the received signal. Frequency selective fading channel are much more difficult to model than flat fading channel.
7. Frequency selective fading channels are also known as ________
a) Narrowband channel
b) Wideband channel
c) Amplitude varying channel
d) Phase varying channel
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Explanation: Frequency selective fading channels are also known as wideband channels. The bandwidth of the signal is wider than the bandwidth of channel impulse response.
8. Frequency selective fading does not induce intersymbol interference.
a) True
b) False
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Explanation: Frequency selective fading is due to time dispersion of the transmitted symbols within the channel. Thus, the channel induces intersymbol interference (ISI). The channel have certain frequency components in the received signal spectrum that have greater gain than others.
9. For fast fading channel, the coherence time of the channel is smaller than _______ of transmitted signal.
a) Doppler spread
b) Bandwidth
c) Symbol period
d) Coherence bandwidth
View Answer
Explanation: In fast fading channel, the channel impulse response changes rapidly within the symbol duration. Thus, the coherence time of the channel is much smaller than the symbol period of the transmitted signal.
10. In slow fading channel, Doppler spread of the channel is much less than the ________ of baseband signal.
a) Symbol period
b) Phase
c) Coherence time
d) Bandwidth
View Answer
Explanation: Slow fading channel may be assumed to be static over one or several reciprocal bandwidth intervals. In the frequency domain, this implies that the Doppler spread of the channel is much less than the bandwidth of the baseband signals.
Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.
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