Virtual Labs

Frequency Selective Fading

1. What is the fundamental cause of 'delay spread'?

a: The transmitter sending the signal too slowly. Explanation

Explanation

b: The signal taking multiple paths of different lengths to the receiver. Explanation

Explanation

c: The receiver moving at a very high speed. Explanation

Explanation

d: Interference from other, adjacent frequency channels. Explanation

Explanation

2. How does increasing the data rate of a signal (which shortens the symbol period) affect its vulnerability to delay spread?

a: It makes the signal less vulnerable to intersymbol interference. Explanation

Explanation

b: It makes the signal more vulnerable to intersymbol interference. Explanation

Explanation

c: It has no effect on the signal's vulnerability. Explanation

Explanation

d: It changes the fading from frequency selective to flat. Explanation

Explanation

3. Which environment is most likely to cause a large delay spread and thus frequency selective fading?

a: An open, flat desert with a clear line of sight. Explanation

Explanation

b: A dense urban city with many tall buildings. Explanation

Explanation

c: Over a calm ocean. Explanation

Explanation

d: A small, indoor room with no furniture. Explanation

Explanation

4. What is a common receiver technique used specifically to combat intersymbol interference caused by frequency selective fading?

a: Using a high-power amplifier. Explanation

Explanation

b: Using an equalizer. Explanation

Explanation

c: Using a simple low-noise amplifier. Explanation

Explanation

d: Using selection combining. Explanation

Explanation

5. A channel's frequency response is *not flat* over the signal's bandwidth. What type of fading is this?

a: Flat fading Explanation

Explanation

b: Frequency selective fading Explanation

Explanation

c: Fast fading Explanation

Explanation

d: Slow fading Explanation

Explanation

6. A large delay spread is inversely proportional to what channel characteristic?

a: The coherence bandwidth. Explanation

Explanation

b: The path loss. Explanation

Explanation

c: The signal strength. Explanation

Explanation

d: The Doppler shift. Explanation

Explanation

7. What is 'Intersymbol Interference' (ISI)?

a: When two different users interfere with each other. Explanation

Explanation

b: When the signal's frequency is changed by the channel. Explanation

Explanation

c: When the delayed copies of one symbol overlap with and distort the next symbol. Explanation

Explanation

d: When the signal is too weak to be detected. Explanation

Explanation

8. To avoid frequency selective fading, a signal's bandwidth should ideally be...

a: much larger than the coherence bandwidth. Explanation

Explanation

b: much smaller than the coherence bandwidth. Explanation

Explanation

c: exactly equal to the coherence bandwidth. Explanation

Explanation

d: much larger than the delay spread. Explanation

Explanation

9. Frequency selective fading is a phenomenon observed in which domain?

a: The time domain only. Explanation

Explanation

b: The frequency domain. Explanation

Explanation

c: The power domain only. Explanation

Explanation

d: The spatial domain only. Explanation

Explanation

10. What type of signal is most affected by frequency selective fading?

a: A narrowband signal. Explanation

Explanation

b: A wideband signal. Explanation

Explanation

c: A signal with a very low data rate. Explanation

Explanation

d: A signal that is not moving. Explanation

Explanation