Digital Communications Multiple Choice Questions on “Diversity technique and rake receivers”.
1. The technique for combining diversity signals are
A. Feedback
B. Maximal ratio
C. Equal gain
D. All of the mentioned
Answer: D
Clarification: The most common techniques used for combining diversity signals are selection, feedback, maximal ratio and equal gain.
2. Diversity technique is used for combating
A. Fading
B. Error bursts
C. Co-channel interference
D. All of the mentioned
Answer: D
Clarification: Diversity technique is a common method used for combating fading, co-channel interference and error bursts.
3. Diversity technique is applied at
A. Base station
B. Mobile receiver
C. Base station & Mobile receiver
D. None of the mentioned
Answer: C
Clarification: Diversity technique can be applied at both base station and at mobile receivers.
4. Which is more effective and commonly preferred technique?
A. Time diversity
B. Spatial diversity
C. Frequency diversity
D. None of the mentioned
Answer: B
Clarification: Most commonly used and more effective diversity technique is spatial diversity technique.
5. Diversity technique
A. Provides significant link improvement
B. Needs training overhead
C. All of the mentioned
D. None of the mentioned
Answer: A
Clarification: Diversity technique does not require training overhead at the transmitter and also provides significant link performance.
6. What are the modes of adaptive equalizer?
A. Training mode
B. Tracking mode
C. Training & Tracking mode
D. None of the mentioned
Answer: C
Clarification: Adaptive equalizer operates on two modes – training mode and tracking mode.
7. Which signalling scheme is preferred for fading channel?
A. Frequency based modulation
B. Phase based modulation
C. Frequency & Phase based modulation
D. None of the mentioned
Answer: C
Clarification: Frequency based modulation and phase based modulation is preferable for fading channel than amplitude based modulation.
8. Uncorrelated fading occurs when
A. Time span is small
B. Time span is large
C. Does not depend on time span
D. None of the mentioned
Answer: B
Clarification: As the time span increases, the fading is more uncorrelated and effectiveness also increases.
9. Interleaving does
A. Forward error correction
B. Backward error correction
C. Forward & Backward error correction
D. None of the mentioned
Answer: A
Clarification: Inter leaver does forward error correction.
10. Rake receiver does
A. Counter effects multi-path fading
B. Resembles equalizer
C. Resembles equalizer & Counter effects multi-path fading
D. None of the mentioned
Answer: C
Clarification: Rake receiver resembles equalizers and it is used to counter the effects of multipath fading and is also used to exploit the path diversity.
11. Information reliability depends on
A. Magnitude of each component
B. Time of arrival of each component
C. Magnitude & Time of arrival of each component
D. None of the mentioned
Answer: C
Clarification: The information reliability can be improved by computing the amplitude and time of arrival of each component.
12. A rake receiver uses multiple
A. Delay circuits
B. Correlators
C. Detectors
D. None of the mentioned
Answer: B
Clarification: A rake receiver uses multiple correlators to separately detect multiple strongest components.
13. Rake receivers are used in
A. Radio astronomy
B. CDMA
C. W-CDMA
D. All of the mentioned
Answer: D
Clarification: Rake receivers are used in radio astronomy, CDMA, W-CDMA, wireless LAN networks etc.
14. The rake receivers functions are similar to
A. Equalizer
B. Matched filter
C. Equalizer & Matched filter
D. None of the mentioned
Answer: C
Clarification: The functionality of rake receiver resembles that of the equalizer and matched filter.