[ESAT] DATA AND DIGICOMMS

1

1 / 1 pts

Frequency of failure and network recovery time after a failure are measures of the _______ of a network.

Feasibility

Reliability

Security

Performance

Reliability

2

1 / 1 pts

Which topology requires a central controller or hub?

Ring

Star

Mesh

Bus

Star

3

0 / 1 pts

Which topology requires a multipoint connection?

Bus

Star

Ring

Mesh

Bus

4

1 / 1 pts

Communication between a computer and a keyboard involves ______________ transmission.

full-duplex

half-duplex

automatic

simplex

simplex

5

1 / 1 pts

A _______ connection provides a dedicated link between two devices

multipoint

secondary

point-to-point

primary

point-to-point

6

1 / 1 pts

In a _______ connection, more than two devices can share a single link.

secondary

point-to-point

multipoint

primary

multipoint

7

1 / 1 pts

_______ refers to the structure or format of the data, meaning the order in which they are presented.

Timing

Syntax

All of these

Semantics

Syntax

8

1 / 1 pts

________ defines how a particular pattern to be interpreted, and what action is to be taken based on that interpretation.

Semantics

Timing

None of these

Syntax

Semantics

9

1 / 1 pts

A _______ is a data communication system within a building, plant, or campus, or between nearby buildings.

LAN

WAN

none of these

MAN

LAN

10

1 / 1 pts

A ______ is a data communication system spanning states, countries, or the whole world.

MAN

none of these

WAN

LAN

WAN

11

1 / 1 pts

A ________ is a set of rules that governs data communication.

forum

none of these

protocol

standard

protocol

12

The Internet model consists of _______ layers.

Eight

Five

Three

Seven

Five

13

1 / 1 pts

The process-to-process delivery of the entire message is the responsibility of the _______ layer.

Application

Network

Physical

Transport

Transport

14

1 / 1 pts

The _______ layer is the layer closest to the transmission medium.

Physical

Transport

Network

Data link

Physical

15

Mail services are available to network users through the _______ layer.

Transport

Physical

Application

Data link

Application

16

1 / 1 pts

As the data packet moves from the upper to the lower layers, headers are _______.

Rearranged

Removed

Modified

Added

Added

17

1 / 1 pts

The _______ layer lies between the network layer and the application layer.

None of these

Transport

Data link

Physical

Transport

18

1 / 1 pts

Layer 2 lies between the physical layer and the _______ layer.

Data link

Transport

Network

None of these

Network

19

1 / 1 pts

When data are transmitted from device A to device B, the header from A's layer 4 is read by B's _______ layer.

Transport

Application

Physical

None of these

Transport

20

1 / 1 pts

The _______ layer changes bits into electromagnetic signals.

Physical

Data link

None of these

Transport

Physical

21

0 / 1 pts

Which of the following is an application layer service?

File transfer and access

Remote log-in

Mail service

All the above

All the above

22

1 / 1 pts

Why was the OSI model developed?

The rate of data transfer was increasing exponentially

Manufacturers disliked the TCP/IP protocol suite.

None of the above

Standards were needed to allow any two systems to communicate

Standards were needed to allow any two systems to communicate

23

1 / 1 pts

The _______ model shows how the network functions of a computer ought to be organized.

CCITT

ISO

ANSI

OSI

OSI

24

1 / 1 pts

The physical layer is concerned with the movement of _______ over the physical medium.

programs

dialogs

protocols

bits

bits

25

1 / 1 pts

The OSI model consists of _______ layers.

eight

seven

five

three

seven

26

1 / 1 pts

In the OSI model, as a data packet moves from the lower to the upper layers, headers are _______.

modified

removed

rearranged

added

removed

27

1 / 1 pts

In the OSI model, when data is transmitted from device A to device B, the header from A's layer 5 is read by B's _______ layer.

session

physical

transport

presentation

session

28

1 / 1 pts

In the OSI model, what is the main function of the transport layer?

process-to-process message delivery

synchronization

node-to-node delivery

updating and maintenance of routing tables

process-to-process message delivery

29

1 / 1 pts

In the OSI model, encryption and decryption are functions of the ________ layer.

transport

application

presentation

session

presentation

30

1 / 1 pts

When a host on network A sends a message to a host on network B, which address does the router look at?

logical

none of the above

port

physical

logical

31

0 / 1 pts

To deliver a message to the correct application program running on a host, the _______ address must be consulted.

IP

port

none of the above

physical

port

32

1 / 1 pts

IPv6 has _______ -bit addresses.

variable

32

64

128

128

33

1 / 1 pts

ICMPv6 includes _______.

RARP

IGMP

ARP

ARP

RARP

34

1 / 1 pts

The ______ layer is responsible for moving frames from one hop (node) to the next.

transport

data link

physical

none of the above

data link

35

0 / 1 pts

The ______ layer adds a header to the packet coming from the upper layer that includes the logical addresses of the sender and receiver.

physical

data link

network

none of the above

network

36

1 / 1 pts

The_________ layer is responsible for the delivery of a message from one process to another.

transport

network

none of the above

physical

transport

37

0 / 1 pts

_______ is a process-to-process protocol that adds only port addresses, checksum error control, and length information to the data from the upper layer.

TCP

UDP

IP

none of the above

UDP

38

1 / 1 pts

__________ provides full transport layer services to applications.

ARP

none of the above

UDP

TCP

TCP

39

0 / 1 pts

The ________ address, also known as the link address, is the address of a node as defined by its LAN or WAN.

none of the above

physical

port

logical

physical

40

0 / 1 pts

Ethernet uses a ______ physical address that is imprinted on the network interface card (NIC).

none of the above

64-bit

32-bit

6-byte

6-byte

41

0 / 1 pts

ARQ stands for _______.

Automatic repeat request

Automatic repeat quantization

Automatic retransmission request

Acknowledge repeat request

Automatic repeat request

42

0 / 1 pts

HDLC is an acronym for _______.

Host double-level circuit

High-level data link control

Half-duplex digital link combination

High-duplex line communication

High-level data link control

43

1 / 1 pts

In a ________ protocol, the data section of a frame is a sequence of characters.

either (a) or (b)

character-oriented

bit-oriented

none of the above

character-oriented

44

1 / 1 pts

In a _________ protocol, the data section of a frame is a sequence of bits.

byte-oriented

either (a) or (b)

bit-oriented

none of the above

bit-oriented

45

1 / 1 pts

In _________ protocols, we use ________.

none of the above

character-oriented; bit stuffing

character-oriented; byte stuffing

bit-oriented; character stuffing

character-oriented; byte stuffing

46

1 / 1 pts

Byte stuffing means adding a special byte to the data section of the frame when there is a character with the same pattern as the ______.

header

trailer

flag

none of the above

flag

47

1 / 1 pts

In ________ protocols, we use ________.

byte-oriented; bit stuffing

none of the above

bit-oriented; bit stuffing

character-oriented; bit stuffing

bit-oriented; bit stuffing

48

1 / 1 pts

Bit stuffing means adding an extra 0 to the data section of the frame when there is a sequence of bits with the same pattern as the ________.

header

flag

trailer

none of the above

flag

49

1 / 1 pts

_______ control refers to a set of procedures used to restrict the amount of data that the sender can send before waiting for acknowledgment.

Transmission

Error

Flow

none of the above

Flow

50

1 / 1 pts

______ control refers to methods of error detection and correction.

Error

Transmission

none of the above

Flow

Error

51

1 / 1 pts

______ is defined as knowledge or intelligence that is communicated between two or more points.

data

codes

Information

message

Information

52

1 / 1 pts

The signal- to-noise ratio is often given in decibels. Assume the SNRdB = 36 dB and the channel bandwidth is 2 MHz. Find the theoretical channel capacity.

42 Mbps

24 Mbps

46 Mbps

55 Mbps

24 Mbps

53

1 / 1 pts

A source generates three symbols with probability 0.25, 0.25, 0.50 at a rate of 3000 symbols per second. Assuming independent generation of symbols, the most efficient source encoder would have average bit rate of

3000 bits/sec

4500 bits/sec

1500 bits/sec

6000 bits/sec

4500 bits/sec

54

1 / 1 pts

This refers to the range of frequencies contained in a composite signal.

Noise

Entropy

Bandwidth

Wavelength

Bandwidth

55

1 / 1 pts

This refers to the maximum, over all possible input distributions, of the mutual information that the channel establishes between the input and the output.

Conditional Entropy

Shannon Limit

Channel Capacity

Joint Entropy

Channel Capacity

56

1 / 1 pts

It states that the total amount of information that can be transmitted is proportional to frequency range transmitted and the time of the transmission.

Shannon-Limit Theorem

Shannon-Hartley Theorem

Hartley's Law

Information Theory

Hartley's Law

57

0 / 1 pts

It is the average number of bit(s) of information per second.

Entropy

Average Information

Information Capacity

Information Rate

Average Information

58

0 / 1 pts

An analog signal is bandlimited to B Hz and sampled at Nyquist rate. The samples are quantized into 4 levels. Each level represents one message, thus there are 4 messages. The probabilities of occurrence of these 4 levels are P1 = P4 = 0.125 and P2 = P3 = 0.375. Find the entropy.

*******search****

2.1 bits/message

1.6 bits/message

1.8 bits/message

2.4 bits/message

2.1 bits/message

59

0 / 1 pts

The terminal of a computer used to enter alphanumeric data is connected to the computer through a voice grade telephone line having a usable bandwidth of 3 kHz and an output of 10dB. Determine the channel capacity.

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60 kbps

20.757 kbps

69.304 kbps

10.378 kbps

10.378 kbps

60

1 / 1 pts

A binary digital signal is to be transmitted at 10kbits/sec. what is the absolute minimum bandwidth is required to pass the fastest information change undistorted?

4 kHz

5 kHz

2 kHz

3 kHz

5 kHz

61

1 / 1 pts

A data compression scheme that involves reduction and splitting.

Huffman Encoding

Run - Length encoding

String Coding

Variable - Length encoding

Huffman Encoding

62

0 / 1 pts

The Hartley - Shannon theorem sets a limit on the

maximum capacity of a channel with a given noise level

highest frequency that may be sent over a given channel

maximum number of coding levels in a channel with a given noise level

maximum number of quantizing levels in a channel of a given bandwidth

maximum capacity of a channel with a given noise level

63

1 / 1 pts

The _________ (for noisy) and ________ (for noiseless) refers to the maximum information rate that is allowed to pass a medium.

Shannon Limit, Hartley Limit

Hartley Limit, Shannon - Hartley

Shannon Limit, Shannon - Hartley

Shannon - Hartley, Shannon Limit

Shannon Limit, Shannon - Hartley

64

1 / 1 pts

A computer monitor has a resolution of 1200 by 1000 pixels. If each pixel uses 1024 colors, how many bits are needed to send the complete contents of a screen?

12M bits

14Mbits

11M bits

13M bits

12M bits

65

1 / 1 pts

This refers to the process accomplished in the transmission whereby code words are assigned to n-symbol groups of symbols.

Sending

Compressing

Receiving

Source Coding

Source Coding

66

1 / 1 pts

Two possible outputs A and B have probabilities of 0.9 and 0.1, respectively. Assume that the source rate is 3.5 symbols/sec. Calculate the source information rate.

1.84 bps

1.642 kbps

1.642 bps

1.84 kbps

1.642 bps

67

1 / 1 pts

It is the measure of goodness of a source code.

Coding Efficiency

Information Measure

Huffman Coding

Average Code Length

Coding Efficiency

68

1 / 1 pts

In this method of encoding, signal remains at the binary level assigned to it for the entire bit time.

Return to zero (RZ)

None of the above

Alternate Mark Inversion

Non-return to zero (NRZ)

Non-return to zero (NRZ)

69

1 / 1 pts

A popular variation of the bipolar RZ format wherein during the bit interval, binary 0s are transmitted as no pulse and binary 1s are transmitted as alternating positive and negative pulses.

Manchester

None of the above

Return-to-zero (RZ)

Alternate Mark Inversion (AMI)

Alternate Mark Inversion (AMI)

70

1 / 1 pts

At the _______, digital data are encoded into a digital signal; at the _______, the digital data are recreated by decoding the digital signal.

(a) or (b)

sender, receiver

None of the above

receiver, sender

sender, receiver

71

1 / 1 pts

Unipolar, bipolar and polar encoding are types of _______ encoding.

Analog-to-Analog

Digital-to-Digital

Digital-to-Analog

Analog-to-Digital

Digital-to-Digital

72

1 / 1 pts

This refers to a form of pulse modulation where the position of a constant width pulse within a prescribed timeslot is varied according to the amplitude of the modulating signal.

Pulse Width Modulation

Pulse Amplitude Modulation

Pulse Position Modulation

Pulse Code Modulation

Pulse Position Modulation

73

1 / 1 pts

In a digital transmission, the receiver clock is 0.1 percent faster than the sender clock. How many extra bits per second does the receiver receive if the data rate is 1 Mbps?

1000 bps

10 bps

1 bps

100 bps

1000 bps

74

0 / 1 pts

Which of the following line encoding scheme is commonly used for long distance communication?

Manchester

Bipolar

AMI

Pseudoternary

AMI

75

0 / 1 pts

Which of the following is not true about bipolar encoding?

It has the same signal rate as RZ.

It has no DC component.

It is sometimes called multilevel binary.

The concentration of the

energy in bipolar encoding is around N/2.

It has the same signal rate as RZ.

76

1 / 1 pts

The ________ rate defines the number of data elements sent in 1s; the ______ rate is the number of signal elements sent in 1s

none of the above

data; signal

signal; data

baud; bit

data; signal

77

1 / 1 pts

In a _____ scheme, all the signal levels are on one side of the time axis, either above or below.

Unipolar

Polar

All of the above

Bipolar

Unipolar

78

1 / 1 pts

In Manchester and differential Manchester encoding, the transition at the middle of the bit is used for __________.

synchronization

bit transfer

baud transfer

none of the above

synchronization

79

1 / 1 pts

Over a digital transmission line, it is more power efficient to encode binary data with voltages that are equal in _________ but opposite in _________ and ___________ about 0 V.

Magnitude; polarity; symmetrically balanced

Magnitude; Polarity; imbalanced

Polarity; magnitude; imbalanced

Polarity; magnitude; symmetrically balanced

Magnitude; polarity; symmetrically balanced

80

1 / 1 pts

The condition in NRZ encoding where a long string of either logic 1s or logic 0s produces a condition in which a receiver may lose its amplitude reference for optimum discrimination between received 1s and 0s.

AC to DC wandering

AC wandering

DC wandering

DC to AC wandering

DC wandering

81

1 / 1 pts

What does it need to recover and maintain clock and framing bit synchronization form the received data?

Sufficient tools

Sufficient transitions in the data waveform

Sufficient pulse

Sufficient bit of data needed in transmission

Sufficient transitions in the data waveform

82

1 / 1 pts

The minimum theoretical bandwidth necessary to propagate a signal is called:

Information Measure

Nyquist Bandwidth

Shannon Limit

Hartley's Law

Nyquist Bandwidth

83

1 / 1 pts

The baud and the ideal minimum Nyquist bandwidth have the same value for all forms of digital modulation except:

None of the above

Amplitude shift keying

Phase shift keying

Frequency shift keying

Frequency shift keying

84

1 / 1 pts

A binary FSK signal has a mark frequency of 49 kHz, a space frequency of 51 kHz, and an input bit rate of 2 kbps. Determine (a) the peak frequency deviation, (b) minimum bandwidth, and (c) baud.

2 kHz, 8kHz, 2000

2 kHz, 6 kHz, 2000

1 kHz, 6 kHz, 2000

1 kHz, 8 kHz, 2000

1 kHz, 6 kHz, 2000

85

1 / 1 pts

This refers to a form of constant-amplitude angle modulation similar to frequency modulation except the modulating signal is a binary signal that varies between two discrete voltage levels rather than a continuously changing analog waveform

FSK

ASK

QAM

PSK

FSK

86

1 / 1 pts

The constellation diagram of QPSK has ______ dots.

2

1

4

16

4

87

0 / 1 pts

The QPSK output phase for the binary input of Q=1 and I=0 is

-135°

45°

135°

-45°

135°

88

1 / 1 pts

For a bandwidth of 7 MHz determine the input bit rate of a QPSK modulator.

14 MHz

3.5 MHz

10 MHZ

7 MHz

14 MHz

89

1 / 1 pts

The baud for 8 PSK equals _____, the same as the minimum bandwidth.

fb

fb/2

fb/4

fb/3

fb/3

90

1 / 1 pts

Determine the bandwidth efficiency of 8-QAM with an input data rate of 30 Mbps.

4 bits/cycle

1 bits/cycle

2 bits/cycle

3 bits/cycle

3 bits/cycle

91

1 / 1 pts

Who is the person that developed TCM at IBM Zurich Research Laboratory?

Harry Nyquist

Alex Reeves

Gottfried Ungerboeck

Guglielmo Marconi

Gottfried Ungerboeck

92

0 / 1 pts

Which circuit is used to create a dibit in a QPSK modulator?

90º shift

JK Flip flop

Balanced modulator

Oscillator

JK Flip flop

93

1 / 1 pts

QAM is a combination of what two types of modulation?

Frequency and Phase

none of the above

Amplitude and Frequency

Amplitude and Phase

Amplitude and Phase

94

0 / 1 pts

Another factor that clearly influences the spectral efficiency is a/an ________.

Bandwidth

Noise

Harmonics

Information data

Bandwidth

95

0 / 1 pts

What circuit is used to demodulate BPSK?

Oscillator

Balanced modulator

Low pass filter

XNOR

Balanced modulator

96

1 / 1 pts

If the bit rate for a 16-QAM signal is 4000 bps, what is the baud rate?

1200

300

400

1000

1000

97

1 / 1 pts

It refers to the information rate before modulation process occurs

baud rate

bit rate

channel capacity

average information rate

bit rate

98

1 / 1 pts

High-frequency radio-teletype systems commonly use:

QAM

ASK

FSK

PSK

FSK

99

1 / 1 pts

Framing bits in DS-1 are used to?

Correct burst error

Synchronize the transmitter and receiver

Carry signaling

Detect errors

Synchronize the transmitter and receiver

100

1 / 1 pts

Which is true about aliasing and foldover distortion?

You can have one or the other, but not both

They are two types of sampling error

Aliasing is a technique to prevent foldover distortion

They are the same thing

They are the same thing