This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Synchronization and network synchronization”.
1. In phase lock which parameter is synchronized
a) Frequency
b) Phase
c) Frequency & Phase
d) None of the mentioned
View Answer
Explanation: Being in phase lock means that the receiver’s local oscillator is synchronized in both frequency and phase with the received signal.
2. Coherent modulation requires ____ level of synchronization.
a) One
b) Two
c) Three
d) None of the mentioned
View Answer
Explanation: Coherent modulation requires three levels of synchronization – phase symbol and frame.
3. Non coherent system requires
a) Phase synchronization
b) Frequency synchronization
c) Phase & Frequency synchronization
d) None of the mentioned
View Answer
Explanation: Non coherent system requires frequency synchronization.
4. For block codes _____ is necessary.
a) Phase synchronization
b) Frequency synchronization
c) Frame synchronization
d) None of the mentioned
View Answer
Explanation: Frame synchronization is necessary when the information is organized in blocks or messages of some uniform number of symbols. Thus block code needs frame synchronization.
5. The synchronization necessary for BPSK is
a) Frequency tracking
b) Bit timing
c) Phase tracking
d) All of the mentioned
View Answer
Explanation: Non coherently detected BPSK is the simplest digital receiver and it requires frequency tracking, bit timing synchronizations and also phase synchronization.
6. Transmitter synchronization implies
a) One way communication
b) Two way communication
c) One & Two way communication
d) None of the mentioned
View Answer
Explanation: Transmitter plays a role in synchronization by varying the frequency and timing of its transmissions to correspond to expectation of receiver. This transmitter synchronization implies two way communication.
7. As the synchronization levels increases, cost
a) Decreases
b) Increases
c) Remains the same
d) None of the mentioned
View Answer
Explanation: For each level increase in synchronization levels, cost increases.
8. Synchronization is used in system which has
a) Non coherent modulation techniques
b) Many users accessing
c) Non coherent modulation techniques & Many users accessing
d) None of the mentioned
View Answer
Explanation: For communication system using non coherent modulation techniques and many users accessing the central communication node, synchronization is necessary.
9. Which method has fast acquisition and can work without return link?
a) Open loop method
b) Closed loop method
c) Open & Closed loop method
d) None of the mentioned
View Answer
Explanation: The main advantage of open loop method is that acquisition is fast, the procedure can work without return link and the amount of real time computation that is required is small.
10. Which method has two way link?
a) Open loop method
b) Closed loop method
c) Open & Closed loop method
d) None of the mentioned
View Answer
Explanation: Closed loop method requires return link, large amount of real time processing and has two way link.
11. Which method requires external authority and is inflexible?
a) Open loop method
b) Closed loop method
c) Open & Closed loop method
d) None of the mentioned
View Answer
Explanation: Open loop method is inflexible, does not adjust quickly to unplanned changes and needs external authority that provides prior knowledge, where as closed loop method does not need all these.
12. Which method needs precorrect time?
a) Open loop method
b) Closed loop method
c) Open & Closed loop method
d) None of the mentioned
View Answer
Explanation: In open loop method the frequency and time are precorrected.
13. In open loop method, the time reference error __________ with respect to time.
a) Increases exponentially
b) Decreases exponentially
c) Increases quadratically
d) Decreases quadratically
View Answer
Explanation: In open loop transmitter synchronization system, the time reference error increases quadratically with time.
14. When a terminal is able to utilize the measurements made on the return link it is called as
a) Open loop method
b) Closed loop method
c) Quasi close loop method
d) None of the mentioned
View Answer
Explanation: The case where a terminal is able to utilize the measurements made on a return link signal is called as quasi closed loop transmitter synchronization.
15. Which reduces the effective distance between signals in signal space?
a) Time error
b) Frequency offset
c) Time error & Frequency offset
d) None of the mentioned
View Answer
Explanation: Time error or frequency offset or combination of both will reduce the effective distance between signals in signal space and degrade error performance.
16. The system which has ______ signal to noise ratio can tolerate larger timing error.
a) Large
b) Small
c) Large & Small
d) None of the mentioned
View Answer
Explanation: The system with increased signal to noise ratio will allow it to tolerate larger timing error so the improvement is error performance is rapid.
Sanfoundry Global Education & Learning Series – Digital Communications.
To practice all areas of Digital Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.
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