This set of Wireless & Mobile Communications Multiple Choice Questions & Answers (MCQs) focuses on “Rake Receiver”.
1. In CDMA spread spectrum systems, chip rate is less than the bandwidth of the channel. State whether True or False.
Explanation: In CDMA spread spectrum systems, the chip rate is typically much greater than the flat fading bandwidth of the channel. Whereas conventional modulation techniques require an equalizer to undo intersymbol interference between adjacent channels.
2. A RAKE receiver collects the __________-versions of the original signal.
a) Time shifted
b) Amplitude shifted
c) Frequency shifted
d) Phase shifted
Explanation: RAKE receiver attempts to collect the time shifted versions of the original signal. It is due to the fact that there is useful information present in the multipath components.
3. RAKE receiver uses separate _________ to provide the time shifted version of the signal.
a) IF receiver
c) Correlation receiver
Explanation: RAKE receiver uses separate correlation receivers to provide the time shifted version of the original signal for each of the multipath signal. CDMA receivers combine these time shifted versions of the original signal to transmission in order to improve the signal to noise ratio of the receiver.
4. Each correlation receiver in RAKE receiver is adjusted in______
a) Frequency shift
b) Amplitude change
c) Phase shift
d) Time delay
Explanation: Each correlation receiver may be adjusted in time delay, so that a microprocessor controller can cause different correlation receivers to search in different time windows for significant multipath.
5. The range of time delays that a particular correlator can search is called ________
a) Search window
b) Sliding window
c) Time span
d) Dwell time
Explanation: The range of time delays that a particular correlator an search is called a search window. RAKE receiver attempts to collect the time shifted version of the original signal by providing a separate correlation receiver for each of the multipath signal.
6. RAKE receiver is used for _______ technique.
Explanation: RAKE receiver is essentially a diversity receiver which is used specifically for CDMA. It uses the fact that the multipath components are practically uncorrelated from one another when their relative propagation delays exceed a chip period.
7. A RAKE receiver uses ____ to separately detect the M strongest signals.
a) Single correlator
b) Multiple correlator
c) Single IF receiver
d) Multiple IF receivers
Explanation: A RAKE receiver uses multiple correlators to separately detect the M strongest multipath components. Demodulation and bit decisions are then based on the weighted ouputs of the M correlators.
8. In a RAKE receiver, if the output from one correlator is corrupted by fading, all the other correlator’s output are also corrupted. State whether True or False
Explanation: In a RAKE receiver, if the output from one correlator is corrupted by fading, the others may not be. And the corrupted signal may be discounted through weighting process.
9. A RAKE receiver uses ____
b) Channel coding
Explanation: RAKE receiver is a diversity receiver. Diversity is provided by the fact that the multipath components are practically uncorrelated from one another when their relative propagation delays exceed chip period.
10. Interleaving is used to obtain _____ diversity.
Explanation: Interleaving is used to obtain time diversity in a digital communication system without adding any overhead. It provides rapid proliferation of digital speech coders which transform analog voices into efficient digital messages.
Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.
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