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CWNA > MidTerm > Flashcards

MidTerm Flashcards

1
Q

Which organization defines the 802.11 standard for communication of wireless network devices?

A

IEEE

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2
Q

Lightning arrestors will defend against which of the following?

A

Transient currents

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3
Q

In the three layer network model, Wireless LAN Controllers are typically associated with which layer?

A

Core Layer

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4
Q

What is the frequency of a wave that cycles 2.4 billion times per second?

A

2.4 GHz

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5
Q

The distance between two equal points on a wave is known as ____________. This is typically measured from peak to peak between wave cycles.

A

Wavelength

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6
Q

If two waves of equal power arrive at a receiver exactly 180 degrees out of phase, they will _______________.

A

cancel each other out

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7
Q

Large groups of people in a single space can cause which issue with wireless signals?

A

Absorption

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8
Q

What is the EIRP in mW from a +3 dBi antenna attached to a 10mW radio?

A

20 mW

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9
Q

A standard measurement of frequency is called what?

A

Hertz

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10
Q

A 2.4 GHz signal will attenuate by approximately…

A

80 dB in the first 100 meters

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11
Q

Semidirectional antennas are often used for which of the following purposes? (Choose Two)

A

~ Providing short-distance point-to-point communications

~ Reducing reflections and the negative effects of multipath in warehouses

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12
Q

Which wave properties can be modulated to encode data? (Choose All That Apply)

A

~ Phase
~ Frequency
~ Amplitude

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13
Q

What is the approximate loss of a 2.4 GHz wave at 50 meters from the transmitter?

A

74 dB of loss

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14
Q

You have 4000 mW of power output from the antenna and you have 33 dB of free space path loss. What is your available power at the receiving antenna?

A

2 mW

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15
Q

The Intentional Radiator is:

A

Everything in the radio system up to, but not including, the antenna

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16
Q

Select the absolute units of power: (Choose three)

A

~ Watt
~ dBm
~ Milliwatt

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17
Q

In the three layer network model, wireless access points are located in which layer?

A

Access Layer

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18
Q

This abbreviation represents an absolute measurement of power referenced to one milliwatt:

A

dBm

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19
Q

An RF wave is bent while propagating from a high pressure area to a low pressure area. This is an example of:

A

Refraction

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20
Q

Which of these propagation behaviors can result in multipath? (Choose Four)

A

~ Reflection
~ Refraction
~ Diffraction
~ Scattering

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21
Q

The signal between the transceiver (radio) and the antenna will be reduced by which of the following? (Choose Three)

A

~ Adding an attenuator
~ Increasing the cable length
~ Using cheaper-quality cable

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22
Q

WLAN vendors use RSSI thresholds to trigger which radio card behaviors? (Choose Two)

A

~ Roaming

~ Dyanmic Rate Switching

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23
Q

If two waves of equal power arrive at a receiver exactly 180 degrees out of phase, they will _______________.

A

cancel each other out

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24
Q

An RF signal bounces off a large metal object (like an elevator). This is an example of:

A

Reflection

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25
Q

The alignment of two waves at a specific point in space and time is known as _________.

A

Phase

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26
Q

What is the definition of the horizontal beamwidth of an antenna?

A

The distance between the two -3 dB power points on the horizontal axis, measured in degrees

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27
Q

To double the maximum distance of a signal, the EIRP must be increased by how many decibels?

A

6 dB

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28
Q

When a long distance point-to-point link is installed, earth bulge should be considered beyond what distance?

A

7 miles

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29
Q

Which organization certifies that wireless devices conform to standards and are compatible with each other?

A

Wi-Fi Alliance

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30
Q

802.11 WLANs are designed for use in which type of frequency band?

A

Unlicensed

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31
Q

If you need an active amplifier, where in your system should it be installed for best performance?

A

Close to the antenna

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32
Q

Name the three layers of the “Three Layer Network Model”. (Choose Three)

A

~ Access
~ Core
~ Distribution

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33
Q

The signal strength that is transmitted from an antenna is known as what?

A

Equivalent Isotropically Radiated Power

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34
Q

When calculating link budget and system operating margin (SOM), padding the budget by reducing the receive sensitivity of the radios in the calculation is known as what?

A

Fade Margin

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35
Q

To double the strength or power of a signal, the EIRP must be increased by how many decibels?

A

3 dB

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36
Q

The carrier signal for 802.11 WLAN communications is?

A

Electromagnetic Waves

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37
Q

If you have a 100 mW 2.4 GHz radio with a 6 dBi antenna attached to an antenna cable with 2 dB of of insertion loss, what is your available power output from the antenna?

A

250 mW

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38
Q

A point source which radiates a signal equally in all directions and has 0dB of gain is known as what?

A

Isotropic radiator

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39
Q

In the three layer network model, wireless bridges are typically associated with which layer?

A

Distribution Layer

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40
Q

RF waves decrease in amplitude as they propagate from the antenna due to the broadening of the wave front. This is known as:

A

Free Space Path Loss

41
Q

The Wi-Fi Alliance is a ________________.

A

Certification Organization

42
Q

One watt is equal to:

A

1,000 mW

43
Q

Which organization defines power output limitations of radio frequency devices operating in the USA?

A

FCC

44
Q

An RF wave hits a chain link fence and multiple waves reflect in different directions. This is an example of:

A

Scattering

45
Q

What term describes the time differential between a primary signal and a reflected signal arriving at a receiver?

A

Delay Spread

46
Q

If you have a 90 mW 2.4 GHz radio with a 12 dBi antenna, what is your available power output from the antenna?

A

1440 mW

47
Q

Which of the following VSWR measurements would provide the best signal to the antenna?

A

1.1:1

48
Q

Which of the following devices produce active gain?

A

RF Amplifier

49
Q

The number of wave cycles that occur in one second is known as _____________.

A

Frequency

50
Q

The number of wave cycles that occur in one second is known as _____________.

A

Frequency

51
Q

RF waves are:

A

Electromagnetic waves

52
Q

You have 3 dBm of power at a distance of 12 meters. If you increase the distance to 48 meters, how much power will you have at the new distance?

A

-9 dBm

53
Q

What are some results of multipath interference? (Choose Two)

A

~ Downfade

~ Intersymbol interference (data corruption)

54
Q

Which antennas are highly directional? (Choose all that apply)

A

~ Parabolic Dish

~ Parabolic Grid

55
Q

The size of the Fresnel zone is controlled by what factors? (Choose Two)

A

~ Distance

~ Frequency

56
Q

Which of the following devices produce passive gain? (Choose all that apply)

A

~ Semidirectional Antenna

~ Parabolic Dish

57
Q

Sector antennas are primarily used for what type of wireless communication?

A

Cellular Telephone

58
Q

An RF wave hits a dense building material (like a brick wall) and some of the RF energy is converted to heat. This is an example of:

A

Absorption

59
Q

RSSI metrics are used by 802.11 radios to measure which RF characteristic?

A

Signal Strength

60
Q

A 2.4 GHz system with a power output of 77 dBm at the antenna has signal strength of -3 dBm at 100 meters. What will the signal strength be at 200 meters?

A

-9 dBm

61
Q

0 dBm (zero dBm) is equal to:

A

1 mW

62
Q

The 802.11a standard uses which frequency band?

A

5 GHz

63
Q

The measurement of signal strength for a WLAN card uses an arbitrary scale of 0 to a maximum value of 255. What is this metric called?

A

RSSI

64
Q

It is possible to have a measurement of signal strength in negative dBm (less than 0dBm).

A

True

65
Q

______________ is the height or power of a wave.

A

Amplitude

66
Q

The following is an Azimuth chart for which type of antenna?

A

Omnidirectional

67
Q

Which of the following are true about antenna cables? (Choose Two)

A

~ They cause impedance on the signal

~ They add loss to the signal

68
Q

The distance between two equal points on a wave is:

A

Wavelength

69
Q

An antenna which broadcasts a signal 360 degrees horizontally is called:

A

Omnidirectional

70
Q

Which three properties are interrelated? (Or put another way: Which three properties share a mathematical relationship?)

A

Frequency, wavelength and the speed of light

71
Q

Which of the following statements are true? (Select TWO answers)

A

~ When the distance between an RF transmitter and receiver is cut in half, the wave gains 6dB of power.
~ When the distance between an RF transmitter and receiver is doubled, the wave loses 6dB of power.

72
Q

The Institute of Electrical and Electronics Engineers (IEEE) is a ________________.

A

Standards Organization

73
Q

When determining the mounting height of a long-distance point-to-point antenna, which of the following needs to be considered? (Choose Four)

A

~ Frequency
~ Earth Bulge
~ Distance
~ RF Line of Sight

74
Q

Which RF component is responsible for generating the AC signal?

A

Transmitter

75
Q

This abbreviation represents the power gain of an antenna relative to an isotropic radiator.

A

dBi

76
Q

The ratio between the maximum peak voltage and minimum voltage on a line is known as what?

A

VSWR

77
Q

The Fresnel zone should not be blocked by more then what percentage to maintain a reliable communications link?

A

40%

78
Q

When calculating link budget, the difference between the actual received signal strength and the required signal indicated by the receive sensitivity is known as what?

A

System Operating Margin

79
Q

You are setting up an outdoor point-to-point link using the 5.8 GHz band over a distance of 25 miles. The best antenna system to use for this link will be:

A

Parabolic Dish or Parabolic Grid Antenna

80
Q

Electromagnetic waves…

A

can propagate through a vacuum.

81
Q

When an RF signal bends around an object such as a building, this propagation behavior is known as what?

A

Diffraction

82
Q

This is a relative expression and a measurement of change in power. It is used in wireless networking to measure gain or loss when comparing two signals.

A

dB

83
Q

The 802.11b standard uses which frequency band?

A

2.4 GHz

84
Q

Azimuth charts represent which of the following?

A

The horizontal plane of the RF signal propagation from an antenna on a logarithmic scale

85
Q

The Federal Communications Commission (FCC) is a _____________.

A

Regulatory Domain Governing Body

86
Q

Which of the following wireless communications parameters are typically governed by a local regulatory domain governing body? (Choose all that apply)

A

~ Maximum power of the intentional radiator (IR)
~ Maximum equivalent isotropically radiated power ~ (EIRP)
~ Bandwidth
~ Frequency
~ Indoor and/or outdoor use

87
Q

You are a WLAN administrator and you have been asked to relocate an antenna approximately 200 feet away from the transmitting AP. You are concerned that a cable run of this distance will reduce the signal strength to a point where the output power at the antenna is not sufficient. What kind of device could potentially be installed in order to make up for the loss incurred from the 200 feet of cable?

A

Amplifier

88
Q

A modulated signal capable of transmitting data is known as a __________.

A

Carrier Signal

89
Q

One gigahertz is equal to:

A

1 billion cycles per second

90
Q

802.11n uses which frequency bands? (Choose Two)

A

~ 2.4 GHz

~ 5.0 GHz

91
Q

In a switched diversity system, the radio…

A

Samples both antennas and the uses the antenna with the best signal

92
Q

What is the approximate loss of a 2.4 GHz wave at 400 meters from the transmitter?

A

92 dB of loss

93
Q

You’ve installed an enterprise-class WLAN. You have provided outdoor access by placing an omnidirectional antenna in the center of a picnic area located on the corporate property. When you installed the outdoor antenna you also installed a lightening arrestor to protect your WLAN equipment. The antenna took a direct hit of lightning yesterday. What should you expect the result to be, since you’ve installed the lightning arrestor?

A

The antenna is likely destroyed and other equipment in-line may also be destroyed

94
Q

Amplifiers can be purchased with which of the following features? (Choose All That Apply)

A

~ Fixed output
~ Bidirectional Amplification
~ Fixed Gain
~ Unidirectional Amplification

95
Q

A data symbol is corrupted by multipath echos from the previous symbol. This is known as?

A

Intersymbol Interference

96
Q

The IEEE 802.11 standard defines communication mechanisms at which layers of the OSI model? (Choose all that apply)

A

~ Data-Link (Layer 2)

~ Physical (Layer 1)

97
Q

This abbreviation represents the value of the increase in gain of an antenna compared to a dipole antenna.

A

dBd

98
Q

The 802.11g standard uses which frequency band?

A

2.4 GHz

99
Q

Grid antennas are often preferable to parabolic dish antennas because…

A

Grid antennas are more resistant to the effects of wind

CWNA (10 decks)

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