6. has units of bits/second. a. Throughput b. Propagation speed c. Propagation time d. (b)or(c)

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1 King Saud University College of Computer and Information Sciences Information Technology Department First Semester 1436/1437 IT224: Networks 1 Sheet# 10 (chapter 3-4-5) Multiple-Choice Questions 1. Before data can be transmitted, they must be transformed to a. Periodic signals b. Electromagnetic signals c. Aperiodic signals d. Low-frequency sine waves 2. A periodic signal completes one cycle in s. What is the frequency? a. 1Hz b. 100Hz c. 1KHz d. 1MHz 3. If the bandwidth of a signal is 5 KHz and the lowest frequency is 52 KHz, what is the highest frequency? a. 5KHz b. 10KHz c. 47KHz d. 57KHz 4. What is the bandwidth of a signal that ranges from 40 KHz to 4 MHz? a. 36 MHz b. 360 KHz c MHz d. 396 KHz 5. Given two sine waves A and B, if the frequency of A is twice that of B, then the period of B is that of A. a. One-half b. Twice c. The same as d. Indeterminate from 6. has units of bits/second. a. Throughput b. Propagation speed c. Propagation time d. (b)or(c) 7. When propagation speed is multiplied by propagation time, we get the a. Throughput b. Wavelength of the signal c. Distortion factor d. Distance a signal or bit has traveled 8. Propagation time is proportional to distance and proportional to propagation speed. a. Inversely; directly b. Directly; inversely c. Inversely; inversely d. Directly; directly 9. Unipolar, bipolar, and polar encoding are types of encoding. a. Line b. Block c. NRZ d. Manchester 10. If a symbol is composed of 4 bits, there are data levels. a. 2 b. 4 c. 8 d. 16

2 11. Pulse rate is always the bit rate. a. Greater than b. Less than c. Greater than or equal to d. Less than or equal to 12. Which of the following encoding methods does not achieve synchronization? a. unipolar b. RZ c. Differential Manchester d. Manchester 13. In PCM, an analog-to- conversion occurs. a. Analog b. Digital c. QAM d. Differential 14. RZ encoding involves. signal levels. a. Two b. Three c. Four d. Five 15. In transmission, bits are transmitted simultaneously, each across its own wire. a. Asynchronous serial b. Synchronous serial c. Parallel d. (a) and (b) 16. In transmission, bits are transmitted over a single wire, one at a time. a. Asynchronous serial b. Synchronous serial c. Parallel d. (a) and (b) 17. In asynchronous transmission, the gap time between bytes is a. Fixed b. Variable c. A function of the data rate d. Zero 18. Synchronous transmission does not have a. A start bit b. A stop bit c. Gaps between bytes d. All the above. 19. ASK and PSK are examples of modulation. a. Digital-to-digital b. Digital-to-analog c. Analog-to-analog d. Analog-to-digital 20. Modulation of an analog signal can be accomplished through changing the of the carrier signal. a. Amplitude b. Frequency c. Phase d. Any of the above 21. A modulator converts a(n) signal to a(n) signal. a. Digital; analog b. Analog; digital c. PSK; FSK d. FSK; PSK

3 Exercises 1. A device is sending out data at the rate of 100 bps a. How long does it take to send out a single character (8 bits)? b. How long does it take to send a file of 300,000 characters? 2. What is the bit rate for the signal in the following figures? a) 14 ns b) 16 ns 3. A file contains 4 million bytes. How long does it take to download this file using a 80-Kbps channel? 1-Mbps channel? 4. If the bandwidth of the channel is 7 Kbps, how long does it take to send a frame of 10,000 bits out of this device? 5. What is the bandwidth of the channel, if the packet with size 6 Kbyte takes 30 second to transmit.? 6. What is the total delay (latency) for a frame of size 4 million bits that is being sent on a link with 6 routers each having a queuing time of 3 µs. The length of the link is 2000 Km. The speed of light inside the link is 2 10 m/s. The link has a bandwidth of 8 Mbps. Ignore processing time at the nodes. Which component of the total delay is dominant?

4 7. Assume we have the data stream Encode this stream, using the following encoding schemes: a. NRZ-l b. Manchester c. Differential Manchester 8. The Figure is the unipolar encoding of a data stream. What is the data stream? 9. The Figure is the NRZ-L encoding of a data stream. What is the data stream? 10. The Figure is the RZ encoding of a data stream. What is the data stream? 11. Using the Nyquist theorem, calculate the sampling rate for the following analog signals. a. An analog signal with frequencies from 1000 to 6000 Hz b. A signal with a horizontal line in the time-domain representation c. A signal with a vertical line in the time-domain representation

5 12. We want to transmit 4000 characters with each character encoded as 8 bits a. find the number of transmitted bits for synchronous transmission b. find the number of transmitted bits for asynchronous transmission (use one start bit and two stop bits) c. find the redundancy percent in each case 13. Calculate the baud rate for the given bit rate and type of modulation: a bps, ASK b bps, FSK 14. Calculate the bit rate for the given baud rate and type of modulation. a baud, FSK b baud, ASK 15. Draw the bit sequence using the following types of digital modulation: ASK, FSK Use below coordinate system.

6 16. Use now ASK with 4 amplitude levels to modulate Comment: First define the 4 amplitude levels and the bits they represent. a. Amplitude to symbol mapping b. Representation of What is the bit rate gain in question 15 compared to question 16?

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