Wireless Fading Channel : Clarke's Model

What happens to the coherence time when the velocity of the user is doubled?

a: It is also doubled Explanation

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b: It gets halved Explanation

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c: It remains unchanged Explanation

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d: Can't be determined Explanation

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If the velocity of the user was halved, what would the effect be on the PSD plot?

a: The plot would get narrower and taller Explanation

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b: The plot would get wider and shorter Explanation

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c: Both may happen; but the overall shape will not change Explanation

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d: Can't be determined Explanation

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What happens if we increase the value of α?

a: Coherence time will increase Explanation

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b: Coherence time will decrease Explanation

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c: Bit error rate of communication will increase Explanation

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d: None of the above Explanation

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A mobile user moves at 60 km/h, and the carrier frequency is 900 MHz. What is the maximum Doppler shift?

a: 50 Hz Explanation

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b: 150 Hz Explanation

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c: 500 Hz Explanation

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d: 900 Hz Explanation

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If the maximum Doppler shift is 200 Hz, what is the approximate coherence time using T_c ≈ 1/(2f_d)?

a: 0.0025 s Explanation

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b: 0.002 s Explanation

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c: 0.005 s Explanation

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d: 0.0005 s Explanation

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In Clarke’s model, reducing the carrier frequency while keeping velocity constant will:

a: Increase maximum Doppler shift Explanation

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b: Decrease maximum Doppler shift Explanation

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c: Keep maximum Doppler shift unchanged Explanation

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d: None of the above Explanation

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In Clarke’s model, the Doppler spectrum shape is U-shaped because:

a: Most multipath components have zero Doppler shift Explanation

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b: Multipath components arrive uniformly from all angles Explanation

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c: Higher Doppler shifts are more probable Explanation

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d: The channel is frequency selective Explanation

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If the coherence time of a channel is 5 ms, what is the approximate maximum Doppler shift?

a: 50 Hz Explanation

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b: 100 Hz Explanation

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c: 200 Hz Explanation

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d: 500 Hz Explanation

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