Name
IT 327
Homework # 18
Chapter 13
Questions
1. Compare the features of AM, FM, and PM for binary digital signals in terms of
complexity, reliability and bandwidth use.
3. Explain the concept of baud vs. bit rate for binary and multiple-level digital signals.
6. What is QAM in concept?
In application?
What do I and Q represent?
8. What do QAM constellation points represent?
Why is the constellation useful?
How does QAM represent a multiple-level digital signal?
10. Why is a loopback useful in digital testing?
How is testing done without a loopback?
13. Compare the interpretation of the source of errors when all three error measures are
about the same percentage to situations where the percentages differ significantly.
14. What is an eye pattern?
How is it displayed?
What does it indicate and what is its usefulness?
18. Explain how PRSQs are used for data encryption and decryption.
Why is this scheme so hard to defeat?
Problems
13.1
1. What is the effective bit rate at 300 baud when bits are represented by a single voltage
that can have one of 16 distinct values?
What is the effective bit rate when eight values are used?
13.2
1. Draw the constellation diagram for a 2 x 4 QAM.
How many bits does each point represent?
How many points are there?
13.3
1. A BER tester sends bits at 2000 baud for 10 s. There is a total of 50 errors. What is the
BER?
2. The data bits of problem 1 are sent as 200-bit frames. All the errors are concentrated in
the first 2 frames what is the percentage of error-free seconds and what is the percentage of
error-free frames?
5. What are the three error measures when the 500 errors occur at the average rate of 100
errors/s for the first 5 s?