# Wireless & Mobile Communications Questions & Answers – Parameters of Mobile Multipath Channels

This set of Wireless & Mobile Communications Problems focuses on “Parameters of Mobile Multipath Channels”.

1. Power delay profile is represented as plots of __________ with respect to fixed time delay reference.
a) Relative received power
b) Frequency
c) Transmitted power
d) Relative power
View Answer

Answer: a
Explanation: Power delay profiles are generally represented as plots of relative received power as a function of excess delay with respect to a fixed time delay reference. They are calculated by averaging instantaneous power delay profile measurements over a local area.

2. Which of the following is not a multipath channel parameter that can be determined from power delay profile?
a) Mean excess delay
b) RMS delay spread
c) Excess delay spread
d) Doppler spread
View Answer

Answer: d
Explanation: The mean excess delay, excess delay spread and rms delay spread are some multipath channel parameters. They can be determined from a power delay profile. Doppler spread is a measure of spectral broadening caused by time rate of change of mobile radio channel.

3. The time dispersive properties of wideband multipath channel are quantified by ______ and _______
a) Mean excess delay, rms delay spread
b) Doppler spread, rms delay spread
c) Doppler spread, coherence time
d) Mean excess delay, Doppler spread
View Answer

Answer: a
Explanation: The time dispersive properties of wide band multipath channels are most commonly quantified by their mean excess delay and rms delay spread. Coherence time characterizes the time varying nature of frequency dispersiveness of mobile radio channel in time domain.
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4. _______ is the square root of the second central moment of the power delay profile.
a) Mean excess delay
b) Rms delay spread
c) Excess delay spread
d) Coherence time
View Answer

Answer: b
Explanation: The rms delay spread is the square root of the second central moment of the power delay profile. Many measurements are made at many local areas in order to determine a statistical range of multipath channel parameters for a mobile communication system over a large scale area.

5. Which of the following is the first moment of the power delay profile?
a) Rms delay spread
b) Excess delay spread
c) Mean excess delay
d) Doppler spread
View Answer

Answer: c
Explanation: Mean excess delay is the first moment of the power delay profile. It is defined from a single power delay profile which is temporal or spatial average of consecutive impulse response measurements collected and averaged over a local area.
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6. What is the order of typical values of rms delay spread in outdoor mobile radio channels?
a) Microseconds
b) Nanoseconds
c) Seconds
d) Minutes
View Answer

Answer: a
Explanation: Typical values of rms delay spread are on the order of microseconds in outdoor mobile radio channels. For indoor mobile radio channels, they are of the order of nanoseconds.

7. Power delay profile and magnitude frequency response of a mobile radio channel are related through _______
a) Laplace Transform
b) Fourier Transform
c) S Transform
d) Wavelet Transform
View Answer

Answer: b
Explanation: Power delay profile and magnitude frequency response of a mobile radio channel are related through the Fourier transform. Therefore, it is possible to obtain an equivalent description of the channel in the frequency domain using its frequency response characteristics.
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8. ______ and coherence bandwidth are inversely proportional to one another.
a) Rms delay spread
b) Mean excess delay
c) Excess delay spread
d) Doppler spread
View Answer

Answer: a
Explanation: The rms delay spread and coherence bandwidth are inversely proportional to one another. However, their exact relationship is a function of the exact multipath structure.

9. Coherence bandwidth is a statistical measure of range of frequencies over which channel is considered _______
a) Time dispersive
b) Frequency selective
c) Time variant
d) Flat
View Answer

Answer: d
Explanation: Coherence bandwidth is a statistical measure of range of frequencies over which channel is considered flat. A flat channel is a channel which passes all spectral components with approximately equal gain and linear phase.
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10. Which of the following describes time varying nature of the channel in a small scale region?
a) Delay spread and coherence time
b) Coherence bandwidth and delay spread
c) Doppler spread and coherence time
d) Delay spread and doppler spread
View Answer

Answer: c
Explanation: Delay spread and coherence bandwidth describes the time dispersive nature of the channel in a local area. They do not give information about the time varying nature of the channel caused by either relative motion between the mobile and base station, or by movement of objects in the channel.

11. Doppler spread is a range of frequencies over which received Doppler spread is _______
a) Zero
b) Non zero
c) Infinite
d) One
View Answer

Answer: b
Explanation: Doppler spread is a range of frequencies over which received Doppler spectrum is essentially non-zero. It is a measure of spectral broadening caused by time rate of change of mobile radio channel.

12. _______ is a statistical measure of time duration over which channel impulse response is invariant.
a) Coherence time
b) Doppler spread
c) Mean excess delay
d) Rms delay spread
View Answer

Answer: a
Explanation: Coherence time is actually a statistical measure of the time duration over which the channel impulse response is essentially invariant. It quantifies the similarity of the channel response at varying times.

Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.

To practice all areas of Wireless & Mobile Communications Problems, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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