Virtual Labs

Pathloss with Shadowing

1. Large-scale propagation models, which include pathloss and shadowing, are used to predict what?

a: The average signal strength over long distances. Explanation

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b: Instantaneous signal changes due to device movement. Explanation

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c: The data throughput of a wireless link. Explanation

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d: The battery life of a mobile device. Explanation

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2. What is the primary difference between large-scale fading and small-scale fading?

a: Large-scale fading happens indoors; small-scale fading happens outdoors. Explanation

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b: Large-scale fading involves distance and obstructions; small-scale fading involves rapid fluctuations from multi-path. Explanation

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c: Large-scale fading only affects high frequencies; small-scale fading only affects low frequencies. Explanation

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d: There is no difference; they are two terms for the same effect. Explanation

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3. The pathloss exponent in a perfect free-space environment, with no obstructions or reflections, is exactly...?

a: One Explanation

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b: Two Explanation

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c: Four Explanation

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d: Zero Explanation

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4. When determining the pathloss exponent from measurements, what is the standard graphical method?

a: Plotting received power versus distance on a linear scale and finding the curve. Explanation

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b: Finding the slope of the best-fit line on a plot of signal power (in dB) versus the logarithm of distance. Explanation

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c: Counting the number of buildings in the signal path. Explanation

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d: Measuring the transmitter's exact power output at the antenna. Explanation

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5. Shadow fading is considered a 'random' process because...?

a: ...the signal strength changes completely unpredictably from one second to the next. Explanation

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b: ...it is impossible to know the transmitter's location. Explanation

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c: ...the exact size, shape, and location of obstructions are complex and vary from one path to another. Explanation

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d: ...it is caused by random noise from the sun. Explanation

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6. What would a shadow fading variance of zero practically imply?

a: The signal is perfectly blocked at all times. Explanation

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b: All signal measurements at a given distance are exactly the same as the average predicted by the pathloss model. Explanation

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c: The environment is extremely cluttered and complex. Explanation

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d: The pathloss exponent must also be zero. Explanation

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7. To properly analyze the statistical characteristics of shadowing, what must be done to the raw signal measurements?

a: The predictable signal loss due to distance (pathloss) must be subtracted out first. Explanation

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b: Only the strongest signal measurement should be kept for analysis. Explanation

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c: Only the weakest signal measurement should be kept for analysis. Explanation

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d: All measurements must be averaged into a single number for the entire area. Explanation

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8. What is a 'propagation model' in the context of wireless communications?

a: A physical antenna used to send signals. Explanation

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b: A set of rules for how to speak on a mobile phone. Explanation

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c: A mathematical description used to characterize signal behavior from transmitter to receiver. Explanation

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d: A software program that blocks unwanted signals. Explanation

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9. A measured pathloss exponent of 2.5 suggests the environment is...?

a: ...identical to a vacuum (free space). Explanation

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b: ...slightly more obstructed than free space, or includes some reflections. Explanation

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c: ...a very dense city with many tall buildings. Explanation

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d: ...an underground tunnel. Explanation

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10. Why is understanding shadow fading variance crucial for wireless network planning?

a: It helps determine the exact data speed a single user will get at a specific moment. Explanation

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b: It is not crucial and is usually ignored in favor of pathloss. Explanation

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c: It helps predict the reliability of signal coverage, allowing planners to design for a certain percentage of users. Explanation

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d: It tells the network planner what brand of antenna to purchase. Explanation

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