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(1) Take online quizzes of multiple choices.
(2) Try the multiple choices at the end of each chapter of textbook. Selected solutions are founded at the site.
1. TV channels are 6 MHz wide. How many b/s can be sent if four-level digital signals are used? Assume a noiseless channel.
2. It is desired to send a sequence of computer screen images over an optical fiber. The screen is 480x460 pixels, each pixel being 24 bits. There are 60 screen images per second. How much data rate is needed?
3. Is Nyquist theory true for optical fiber, or only for copper wire?
4. Radio antennas often work best when the diameter of the antenna is equal to the wavelength of the radio wave. Reasonable antennas range from 1 cm to 5 meters in diameter. What frequency range does this cover?
5. Why has the PCM sampling time been set at 125 µsec?
6. Compare the maximum data rate of a noiseless 4-kHz channel using: a) Analog encoding with 2 bits per sample. b) The T1 PCM system.
7. What is the difference, if any, between the demodulator part of a modem and the coder par of a codec? (After all, both convert analog signals to digital ones).
8. Compute the bit rate for a 1000-baud 16-QAM signal.
9. Compute the baud rate for a 72,000 bps 64-QAM signal.
10. Explain the difference between data rate and baud rate?
11. What is the percent overhead on a T1 carrier; that is, what percent of the 1.544 Mbps are not delivered to the end user?
12. How many lines can a TSI switch handle if the RAM access time is 50 nsec?
13. How many bits of RAM buffer does a TSI switch need if the input line samples are 10 bits and there are 80 input lines?
14. Does time division switching necessarily introduce a minimum delay at each switching stage? If so, what is it?
15. How many crosspoints are needed if we use a crossbar switch to connect 1000 phones in a small town?
16. Why does fiber-optic cable have greater capacity than copper-based media?
17. Compare and contrast MMF with SMF.
18. Compare and contrast GEO and LEO satellite communications systems.
