Question Bank

DATA COMMUNICATION

I. FILL IN THE BLANKS:

1. In half-duplex data transmission data can be transmitted in --------------.direction.
Both

1. In digital data transmission baud rate is equal to --------------
Bit rate
2. In simplex transmission data can be Transmitted in --------------direction.
One
3. The cost of conveying message, picture or voice over a large distance in a communication system should be --------------
Small
4. In any communication system, the message should be safe and --------------should reach to the person for whom it is meant.
Secure
5. PCs connected with --------------can also be used for education, entertainment, etc.
Modem

6. sending a message and receiving a response has always been --------------for the proper functioning of a business or administration.
Necessity

7. Eavesdropping is not possible in…-------------- fiber optics

8. Coaxial cables can be used for………-------------- Both in telephone and cable TV networks.
9.
10. Data networks for the efficiency of communication reasons, uses--------------. Full-duplex transmission

11. The meaning of a digital channel means that the channel is --------------. Carrying digital data.

12. Data networks for the efficiency of communication reasons, uses-------------- Full-duplex transmission

13. -------------is not a bounded media of transmission of RF energy. Laser Beam

14. Frequency range of human voice and audible to human ears is usually in the range of--------------…-------------- 100MHz to 400 MHz
15. Fiber optics communication system uses--------------. Full-duplex

16. In satellite communication, up-link frequency and down-link frequencies are different because……-------------- interference can be avoided

17. Higher the band width, the--------------……….is the efficiency response in a stereo system. Higher

18. --------------networks uses the entire bandwidth of the cable for a single channel.
Base band
18. --------------is basically a frequency division multiplexed situation. Broadband
19. STP and --------------…can be used for both Analog and digital data transmission UTP

20. A balanced modulator can be used to generate-------------- PSK

21. Microwave links are generally preferred o coaxial cable for television transmission because……-------------- Of their greater bandwidth

22. When useful bandwidth of medium exceeds the required bandwidth of signals to be transmitted we use --------------…. Frequency Division Multiplexing

23. To synchronize receiver and transmitter, besides synchronous transmission , the other approach is ------------------------- transmission Asynchronous

24. The optical fiber transmission there exists --------------repeater spacing. Higher

25. A satellite link introduces large -------------- capacity

26. ------------------------ Transmission is more appropriate for high-speed communication. Synchronous

27. Start and stop bits are required in --------------communication. Asynchronous

28. Order of frequencies used in satellite communication is -------------- 109

29. Fiber optic communication uses order of -------------- frequencies. 10 14

30. Phase sent for a particular bit is dependent on the previous bit in -------------- DPSK

31. QAM is -------------- PSK combined with AM

32. --------------modulation requires the lowest bandwidth. PSK

33. Digitalization refers to -------------- Sampling and Quantization

34. If R is the bit rate in a digital wave form then the bit period of T is equal to ------------ 1/R

35. In long distance data transmission system, the most preferable mode of communication is -------------- Serial transmission

36. The sampling interval of a telephone voice signal is -------------- 125*10-6 sec

37. In a telephone channel, Voice signal are band limited to ----------------- 8KHz

38. During transmission, the distortion of the signal depends on -------------- Frequency of the signal

39. Statistic multiplexers may also be classified as -------------- Concentrators

40. The approximate round trip delay in satellite communication is -------------msec. 256

41. --------------modulation technique is used in high-speed modems. Differential phase shift keying

42. The difference between the decoded signal and the original is referred to as the ------------ Quantization error

43. -------------------fiber suffers from high signal dispersion. Multimode

44. --------------allows data to be transmitted using a smaller bandwidth. Compression

45. Parity checking is used for error -------------- Detection
46. The --------------……process in a PCM modulator introduces an error in the original signal and the final demodulated signal. Quantization

47. Analog to digital conversion using PCM introduces -------------noise. Quantization

48. Intermodal dispersion is not found in -------------- fibers. Single mode

49. The VHF band of communication frequencies lies in the rang of -------------- 30-300MHz

50. A different carrier frequency is used for each channel in --------------. multiplexing. Frequency Division

51. With a 7-bit code per sample, the bit rate becomes --------------.Kbps for voice signals. 56
52. FDDI is a high performance --------------LAN that runs at 100 Mbps. Token ring
53. The basic (minimum) data rate in the digital telephony is -------------- 64 kb/s
54. A PABX can be used for -------------- Voice connection and Data connection only

55.Satellite communication use -------------- Microwaves
56. -------------layer of the OSI model does data compression. Presentation
57.The --------------.layer defines how the cable is attached to the network adapter card. Physical
58. The data link layer is responsible for sending --------------from the network layer to the physical layer. Control
TRUE OR FALSE:

1. Synchronous Transmission is more efficient than asynchronous Transmission. True
2. CRC is used to verify the integrity of the entire block of data. True
3. The best example of TDM is the way we receive various radio stations in a radio.
False

4. Maintenance of analog communication systems is costly and difficult as compared to digital systems.
True

5. Digital Transmission is more prone to noise interference than analog Transmission
False

6. Twisted wire pair is effected by the electromagnetic interference.
True
7. Single mode used in Fiber optics does not have any dispersion problem.
True

8. Attenuation is highest in UTP cable. False

9. Multipath fading is not a serious problem in Microwave Communication systems.
False

10. A satellite in geo-synchronous orbit is a distance of 36000 miles from the equator of the earth. False

11. In single-mode optics fibers, the core is 8 to 10 microns and a micron is one millionth of an inch. False
12. A phase shift keying receiver must incorporate carrier recovery.
True

13. A phase shift keying signal is less susceptible to noise than amplitude shift keying signal.
True
14. FSK scheme requires less bandwidth than PSK.
False

15. Quantization noise in a PCM system increase when the number of levels of quantization is increased.
False

16. In DPSK, the information in the two consecutive bits is used.
True

17. Higher bit rates can be achieved over voice grade line by employing more complex modulation schemes.
True

18. Asynchronous transmission is far more efficient than synchronous transmission.
False

19. The peak-to-peak voltage of the carrier wave is varied with signal value in phase modulation. False

20. Single mode fibers are more expensive but can be used for longer distances. True

21. Colocated earth stations are used for frequency diversity.
False

22. Synchronous transmission is more appropriate for high speed communication. True

23. Sharing of executable files in LAN is not possible.
False

24. FDD uses two rings.
True

25. The IEEE 802.3 Standard is for persistent CSMA/CD LAN. True

26. Telnet is a Internet Protocol for logging on to remote hosts and processing data locally. True
27. The receiving computer passes the reassembled data to the session layer in a usable form. False

28. A receiving computer copies the data from the packets to a buffer for reassembly. True
29. NetBEUI is a transport protocol that provides data transport services for NetBIOS sessions and applications. True

30. Coaxial cable can be used for data rates over 10 Mbps and frequencies up to 400MHz
True

31. When the same numbers of channels are to be multiplexed for transmission, FDM always requires a greater bandwidth than TDM.
False

32. Attenuation in a pair is effected by the electromagnetic interference. True

33. Digital speech occupies more bandwidth compared to nondigitized speech. True
34. Optical fiber communication system always uses laser transmitters. False

35. The end –to-end propagation delay between two stations using satellite communication is small compared to coaxial systems.
False

36. Time division multiplexing does not incur any overhead False

37. Digital telephony always uses time division switching. True

38. ALOHA is a protocol. True

39. SMAU is smart Multistation Access Unit. True

40. Modulating the carrier is used for frequency division multiplexing. True

41. Digital multiplexing is considered to be simpler than analog multiplexing True

42. Attenuation in a digital channel causes changes the shape of the digital signal. False

43. LANs are arranged in star, bus, or ring configurations. True

44. In fully connected network, communication is very fast between any two nodes. True

45. Ethernet uses bus topology. True

46. A network is any collection of computer and other devices connected together to pass on information. True

47. Point-to-point microwave link is the best option to provide large connectivity. False

48. Phase modulation is more noise resistant compared to amplitude modulation. True

49. Circuit switching is a store and forward switching. False

50. Packet switching is a form of store and forward switching. True

51. Ethernet 10Bae T is a popular network based on the star topology. True

52. The foundation of Ethernet is CSMA/CD. True

53. Modern EPABX s use Frequency multiplexing. False

54. RS-232 interface is a common standard for personal computers. True

55. The physical layer makes routing decisions. False

56. Gateways operate in the network layers. True

57. Transport layer provides dialog between application programs. True

58. Routers are devices that connect two or more networks. True

59. A Bouter is a Router. True

60. Logical Link Control is a error and flow control. True

SHORT QUESTIONS:

1. Explain the terms bit rate and baud rate.
2. Differentiate between analog and digital transmission of data. Give their relative advantages and disadvantages.
3. What are Modems? What purpose do they serve in data communication systems?
4. Why is multiplexing needed in data communication systems?
5. Explain the advantages and disadvantages of Asynchronous mode of data transmission.
6. Explain the characteristics of Fiber Optics Cable.
7. Explain twisted-pair wire? Also explain its advantages?
8. Explain Amplitude, Phase and Frequency Modulations?
9. Advantages of frequency and phase modulation.
10. Difference between digital signal Modulation and Analog signal Modulation
11. Explain the concept of QPSK modulation using a pharos diagram.
12. Explain a scheme to detect BPSK signals.
13. Discuss with a circuit diagram the working of a DPSK modulator.
14. Explain the working of a BPSK phase detector.
15. What do you understand by the term channel bandwidth? How is it affected by the signal to noise ratio.
16. Explain Frequency Division multiplexing?
17. Explain Synchronous Time Division Multiplexing?
18. Explain PCM
19. Advantages and disadvantages of Star topologies.
20. Explain multiple access techniques.
21. Explain the advantages and disadvantages of FDDI.
22. Explain a scheme to detect FSK signals
23. Explain the concept of circuit switching.
24. Explain how is the flow controlled in X.25 networks?
25. Explain the different functional modules and operation of a FAX transmitter.
26. Compare satellite communication with fibre optic communication.
27. Explain Digital telephony.
28. Explain Channel bandwidth?
29. List the major advantages/disadvantages with the layered approach to protocols.
30. Compare Optical fiber and terrestrial link.
31. Explain ATM. Also explain its working?
32. State the advantages of semiconductor laser diode over light-emitting diodes (LED) for fiber transmission.
33. Explain difference between packet and circuit switching.
34. Explain satellite communication?
35. Explain Physical layer?
36. Explain ISDN?
37. Explain Signal bandwidth?
38. Explain the advantages and disadvantages of synchronous mode of data transmission.
39. Illustrate time division multiplexing and Frequency division multiplexing.
40. Explain semiconductor laser diode?
41. Explain the function of the data link layer.
42. Advantages and disadvantages of BUS topologies.
43. Explain Bus topology?
44. What is cache memory? What are its uses?
45. Explain LAN. Explain any two LAN commands.
46. What are Error correcting and Error detection codes?
47. Explain the steps for getting a connection to the Internet.
48. What is Protocol? What are the elements of Protocol?
49. Explain phase shift keying.
50. Explain Pulse code Modulation.
51. Explain Packet switching?
52. Explain Static Routing of packets?
53. Explain Star topology?
54. Explain Advantages and Disadvantages of Ring Topology?
55. How Timedivision Multiplexing is is achieved?
56. Show and explain the Ethernet topology using coaxial cables?
57. What is guard band?
58. Explain the concept of QAM with suitable diagrams.
59. Summarize the differences between Ethernet LAN and Token Ring LAN.
60. Difference between Router and Bridge.
ESSAYS:

1. Explain different types of topologies.
2. What is the difference between serial and parallel transmission? Why do most communication systems use serial transmission?
3. Explain different types of Networks with suitable examples.
4. Why multiplexing used in telephone trunk circuits to transmit a large number of voice channels.
5. Explain Network layer of the OSI reference model.
6. Explain how networks may be classified by the technique employed in transporting message between the nodes. Compare any two of them?
7. Define Multiplexing? Explain the various types of Multiplexing.
8. How are the radio wave propagated? Illustrate the above using diagrams
9. Explain Modulation?
10. Explain the working of a PBX network.
11. Explain the comparison of Fiber Optics and Copper wire.
12. What is the principle difference between connectionless communication and connection oriented communication.
13. Show various layers in the ISO-OSI model?
14. Explain different types of transmission medias
15. Explain types of microwave communication systems?
16. Show and explain FDDI ring configuration.
17. Explain the types of Microwave Communication Systems.
18. Differentiate between simplex, half-duplex, and full-duplex modes of data Transmission.
19. Discuss the need or lack of need for a network layer of the OSI reference model in a broadcast network.
20. What is the role of the communication Subnet in a computer network? Which layers of OSI model does it cover?
21. Compare and contrasts CSMA/CD and token passing access methods.
22. What is WAN? How does it differ from LANs and MANs? Give at least two examples of popular WANs.Explain the term internetwork?
23. What is differential PSK? How is it achieved? Take a suitable stream of binary data of your choice and indicate the phases of a binary DPSK waveform.
24. Explain TDMA and FDMA.
25. What is the basic rate interface in ISDN? Explain.
26. Discuss various aspects of microwave transmissions.
27. Define the following terms
28. Cladding
29. Pulse spreading
30. Refractive index
31. Why the digital communication systems are more resistant to channel noise than analog systems.
32. What is the resulting effect of the light signal due to scattering.
33. Explain using a table, the various protocols used in different layers of the OSI model.
34. Explain ASK and FSK.