Chapter 16 - Wireless Networks

Question 1

A(n) _____ wireless local area network (WLAN) is enabled with a single access point (AP) is used to manage communications between stations.

a. Extended service set (ESS)
b. Basic service set (BSS)
c. Independent basic service set (IBSS)

Answer 1

b. Basic service set (BSS)

p 16-69

A BSS WLAN is enabled when a single AP is used to manage the communications between two or more stations equipped with wireless NICs. The use of an AP makes it possible to increase the number of stations and the physical span of the WLAN since the AP centrally
manages all communications.

Question 2

Watts provide an absolute measurement of power

a. True
b. False

Answer 2

True

p 16-20

While watts provide an absolute measurement of power, decibels provide a measurement of relative gain or loss of power.

Question 3

When choosing the antenna support structure for an installation, additional consideration should be given if the structure will be located within the ___ approach area near an airport or heliport (in the United States)

a. 5 km (3 mi)
b. 8 km (5 mi)
c. 10 km (6 mi)
d. 16 km (10 mi)

Answer 3

b. 8 km (5 mi)

p 16-31

If in the ≈8 km (5 mi) approach area near an airport or heliport (in the United States)

Question 4

The ___ of a wireless network is defined by the system’s accessibility, continuity, and consistency of service.

a. Scalability
b. Compatibility
c. Reliability
d. Implementation

Answer 4

c. Reliability

p 16-3

The reliability of a wireless network is defined by the system’s accessibility, continuity, and consistency of service

Question 5

___ is the abrupt change in direction of a wave front at the interface between two dissimilar media such that the incident wave front returns into the medium from which it originated.

a. Reflection
b. Refraction
c. Scattering
d. Diffraction
e. Absorption

Answer 5

a. Reflection

p 16-9

Question 6

___ is the abrupt change in direction of a wave front at the interface between two dissimilar media as the incident wave front enters the second medium.

a. Reflection
b. Refraction
c. Scattering
d. Diffraction
e. Absorption

Answer 6

b. Refraction

p 16-9

Question 7

___ is the change in the level, direction, frequency, or polarization of incident radiation when it encounters small particles or inhomogeneous particles whose size is similar to or smaller than the wavelength of the incident radiation.

a. Reflection
b. Refraction
c. Scattering
d. Diffraction
e. Absorption

Answer 7

c. Scattering

p 16-9

Question 8

___ is the bending of sound, radio, or light waves around an object, barrier, or aperture edge.

a. Reflection
b. Refraction
c. Scattering
d. Diffraction
e. Absorption

Answer 8

d. Diffraction

p 16-9

Question 9

___ is the loss of energy in an electromagnetic signal as it passes through a medium.

a. Reflection
b. Refraction
c. Scattering
d. Diffraction
e. Absorption

Answer 9

e. Absorption

p 16-9

At RF frequencies, absorption occurs when gaseous molecules or suspended water particles (e.g., fog) in the atmosphere absorb the signal energy and convert it into heat because of molecular resonance.

Question 10

___ is the loss incurred by an RF signal due to the natural broadening of the wave front.

a. Dispersion
b. Path loss
c. QoS
d. Fading

Answer 10

a. Dispersion

p 16-12

Dispersion is the loss incurred by an RF signal due to the natural broadening of the wave front. The wider the wave front, the less power can be induced into the receiving antenna.

Question 11

The received power level is inversely proportional to the square of the ___ and directly proportional to the square of the ___.

a. Distance traveled, transmitted signal’s wavelength
b. Transmitted signal’s wavelength, distance traveled

Answer 11

a. Distance traveled, transmitted signal’s wavelength

p 16-12

Question 12

___ is defined as the variation (with time) of the amplitude or relative phase, or both, of one or more of the frequency components of a signal.

a. Dispersion
b. Path loss
c. QoS
d. Fading

Answer 12

d. Fading

p 16-12

Fading is defined as the variation (with time) of the amplitude or relative phase, or both, of one or more of the frequency components of a signal.

NOTE: Fading is caused by changes in the characteristics of the propagation path with time.

Question 13

___ is the propagation phenomenon that results in RF signals reaching the receiving antenna by two or more paths.

a. Multipath fading
b. Delay Spread
c. Direct path
d. Dispersion

Answer 13

a. Multipath

p 16-12

The causes of multipath fading include RF signal reflection from natural objects (e.g., mountains) and man-made objects (e.g., buildings).

Question 14

___ is the result of multiple paths causing reflection, refraction, and scattering of the transmitted signal. Multiple signals are received by the receiver with different amplitudes and delays at different time intervals.

a. Multipath fading
b. Delay Spread
c. Direct path
d. Dispersion

Answer 14

b. Delay Spread

p 16-13

Delay spread—The result of multiple paths causing reflection, refraction, and scattering of the transmitted signal. Multiple signals are received by the receiver with different amplitudes and delays at different time intervals.

Question 15

Heavy moisture in the atmosphere causes disruptions in the transmission of RF signals, mainly above ___.

a. 2.4 GHz
b. 5 GHz
c. 6 GHz
d. 18 GHz

Answer 15

c. 6 GHz

p 16.24

Heavy moisture in the atmosphere causes disruptions in the transmission of RF signals, mainly above 6 GHz. This disruption, called rain fade, can be caused by rain, fog, heavy snow, and other moisture related elements.

Question 16

PTP licensed wireless networks are found in the 6 GHz to 40 GHz ranges and can offer speeds of ___ to ___

a. 10 Mb/s, 1 Gb/s
b. 100 Mb/s, 1 Gb/s
c. 10 Mb/s, 10 Gb/s
d. 100 Mb/s, 10 Gb/s

Answer 16

a. 10 Mb/s, 1 Gb/s

p 16-25

PTP licensed wireless networks are found in the 6 GHz to 40 GHz ranges and can offer speeds of 10 Mb/s to 1 Gb/s.

The 6 GHz and 11 GHz frequencies primarily are used for public safety applications, and the 18 GHz and above frequencies are used primarily in the private sector for PTP applications.

Question 17

For line of sight most PTP radios above ___ GHz require a clear path. Multipoint wireless equipment with frequencies above ___ GHz typically requires LoS.

a. 2, 5
b. 1, 5
c. 2, 4
d. 1, 2

Answer 17

d. 1, 2

p 16-26

Question 18

RF equipment under IEEE 802.11 can penetrate walls and other materials at short distances and are considered non-LoS RF.

a. True
b. False

Answer 18

False

p 16-26

Indoor RF equipment falling under IEEE 802.11 can penetrate walls and other materials at short distances, but they are not considered non-LoS RF. The lower ranges of the spectrum, below 2 GHz, are the most common for non-LoS applications.

Question 19

Path loss of ___ dB isotropic is common when using radomes.

a. 0.5
b. 1
c. 3
d. 6

Answer 19

a. 0.5

p 16-27

These covers, however, cause some loss in the RF signal as it passes through the cover. This loss should be accounted for in the path loss calculation. Path loss of 0.5 dB isotropic is common when using radomes

Question 20

Time division duplex can transmits and receives both analog and digital RF alternately in sequential time slots on a single frequency.

a. True
b. False

Answer 20

False - digital only

p 16-28

Transmits and receives at RF alternately in sequential time slots on a single frequency. Because of buffering of the baseband signal, the baseband interface is full-duplex. Digital only. Found in selected digital cordless telephone systems, telemetry, WLAN, and data links.

Question 21

Frequency division duplex transmits and receives simultaneously with transmitter and receiver operating on ___ pair of frequency(ies) or duplex channel assigned in accordance with a band plan.

a. Same
b. Separate

Answer 21

b. Separate

p 16-28

Applies to both analog and digital systems. Used for repeaters, PTP links, duplex, two-way radio, and cellular telephone systems. This is also called full-duplex.

Question 22

Tower lighting is required when working more than ___ in height or within the 5 mi (≈8 km) jurisdiction of an airport or heliport (this will be determined when filing a construction permit with the local aviation authority).

a. 50 ft
b. 100 ft
c. 150 ft
d. 200 ft

Answer 22

d. 200 ft

p 16-32

Question 23

Down conversion of RF transported over fiber, typically have losses between ___ to ___ dB.

a. 0.5, 1
b. 1, 3
c. 3, 5
d. 5, 7

Answer 23

c. 3, 5

p 16-53

The optical losses for these systems are similar to analog, typically 3 to 5 dB. Optical fiber connectors for down conversion systems may be ST type or SC type with APC polished ferrules meeting the required optical return loss of more than 35 dB.

Question 24

For digital sampling of RF signals the typical loss budgets are more than ___ dB; with long-range systems more than __ dB.

a. 6, 12
b. 12, 25
c. 25, 30
d. 30, 50

Answer 24

b. 12, 25

p 16-53

The optical budget for digital systems depends on the type of transceiver and SFF connectors and whether avalanche photo diodes are used. Typical loss budgets are more than 12 dB; with long-range systems more than 25 dB. Optical connectors for SFF-based systems are LC type.

Digital systems are more immune to reflection and scattering and do not require APCs. The optical return loss requirements are 12 dB.

Question 25

Analog modulation of RF signals typical required optical return loss, which includes reflection and backscatter, is more than ___ to___ dB

a. 6, 12
b. 12, 25
c. 25, 30
d. 35, 45

Answer 25

d. 35, 45

p 16-53

Typical required optical return loss, which includes reflection and backscatter, is more than 35 to 45 dB. These optical fiber transmission criteria may vary by DAS manufacturer.

Question 26

Infrared (IR) communications defined by the Infrared Data Association (IrDA) used line-of-sight (LoS) transmission, with a maximum allowable level of surrounding illumination of _____ lux.

a. 1
b. 10
c. 50
d. 100

Answer 26

b. 10

p 16-66

IR is a purely LoS system. IR is unaffected by RF, but it can be affected by ambient light. The IrDA standard specifies a maximum level of surrounding illumination of 10 lux. Use a light meter if daylight is present in the proposed area.

Question 27

___ combines the output of two or more transmitters into a single antenna system while achieving the desired signal strength and system performance.

a. Diplexing
b. Duplexing
c. Multiplexing
d. Coupling

Answer 27

a. Diplexing

p 16-59

The objectives of diplexing are to:
––Maintain proper transmission limits set by the manufacturer or regulatory body.
––Provide adequate bandwidth at each frequency that is diplexed.
––Control and minimize signal loss.

Question 28

___ combines the forward and reverse signal paths onto a single cable.

a. Diplexing
b, Duplexing
c. Multiplexing
d. Coupling

Answer 28

b, Duplexing

p 16-59

Question 29

The term ___ mode is used to describe a BSS WLAN since it is necessary to obtain and install an AP prior to enabling wireless communications.

a. Logical
b. Structured
c. Infrastructure
d. Basic

Answer 29

c. Infrastructure

p 16-69

An AP can be a stand-alone unit or it can be connected to a cabled network using a cabling link. In both cases, the term infrastructure mode is used to describe a BSS WLAN since it is necessary to obtain and install an AP prior to enabling wireless communications.

Question 30

The APs in an ESS can be linked using cabled or wireless networking. In both cases, the network used to link the APs is referred to as the ___ system.

a. Mesh
b. PTMP
c. Extended
d. Distribution

Answer 30

d. Distribution

p 16-69

The APs in an ESS can be linked using cabled or wireless networking. In both cases, the network used to link the APs is referred to as the distribution system. When cabling is used to create a distribution system, each AP is described as a portal or gateway—it converts signals between the IEEE 802.11-based WLAN and the distribution system network (e.g., IEEE 802.3 Ethernet LAN).

Question 31

IEEE 802.15 specifies a throughput of up to ___ kb/s, operates in the 2.4 GHz band, and uses frequency-hopping spread spectrum.

a. 512
b. 720
c. 1020
d. 2040

Answer 31

b. 720

p 16-65

IEEE 802.15 specifies a throughput of up to 720 kb/s, operates in the 2.4 GHz band, and uses frequency-hopping spread spectrum.

Question 32

Up to ___ IEEE 802.15 devices can be supported in one piconet. Piconets can be combined to form larger networks called scatternets.

a. 2
b. 4
c. 6
d. 8

Answer 32

d. 8

p 16-65

Question 33

When electronic equipment turns ac to dc, it draws current in ___.

a. Harmonics
b. Noise
c. Phases
d. Pulses

Answer 33

d. Pulses

p 16-19

When electronic equipment turns ac to dc, it draws current in pulses. These pulses can cause distorted current wave shapes that are rich in harmonics of the fundamental frequency (see Figure 16.10).

Question 34

Omnidirectional antennas broadcast equally in all directions of only ___ cross section of their toroidal (doughnut-shaped) three-dimensional radiation pattern

a. One
b. Two
c. Three

Answer 34

a. One

p 16-42

Omnidirectional antennas generally are mounted so that they radiate with equal strength in all horizontal directions.

Question 35

___ used as a transmission line to feed radio frequency (RF) power contains balanced currents in its two conductors, resulting in no net external field.

a. Coaxial cabling
b. Open wire

Answer 35

b. Open wire

p 16-29

Open wire or balanced lines generally comprise parallel unshielded conductors fed and terminated in a balanced manner with respect to Earth. In principle, the current in one conductor exactly balances that in the other conductor resulting in no net external field.

Question 36

The frequencies from ___ are most prevalent in the wireless deployments for the unlicensed spectrum.

a. 12 GHz to 18 GHz
b. 6 GHz to 11 GHz
c. 2.4 GHz to 5 GHz
d. 900 MHz to 3 GHz

Answer 36

c. 2.4 GHz to 5 GHz

p 16-25

Although the spectrum range below 2.4 GHz has unlicensed space available, these frequencies are used primarily by amateur radio operators, 900 MHz wireless Internet SPs, and SCADA communications.

Question 37

___ is the standard modulation technique for 802.11a/g/n/ac wireless local area networks (WLANs).

a. Complementary code keying (CCK)
b. Binary phase shift keying (BPSK)
c. Quadrature amplitude modulation (QAM)
d. Orthogonal frequency division multiplexing (OFDM)

Answer 37

d. Orthogonal frequency division multiplexing (OFDM)

p 16-18

OFDM has been adopted as the standard modulation technique for 802.11a, g, n, ac, 802.22, European digital TV standards, and 4G cellular.

It is inherently insensitive to multipath distortion and can be quickly scaled up or down in bandwidth by adding or subtracting the quantity of subcarriers.

Question 38

Singlemode optical fiber cabling used for distributed antenna system (DAS) distribution can interconnect remote transceivers to a base transceiver station (BTS) over a maximum span of:

a. 20 km (12.4 mi)
b. 10 km (6.2 mi)
c. 5 km (3.1 mi)
d. 1 km (0.6 mi)

Answer 38

c. 5 km (3.1 mi)

p 16-41

• Singlemode optical fiber cabling—Used for both indoor and outdoor applications, interconnecting remote transceivers, up to ≈5 km (3.1 mi), back to the BTS.
• Multimode optical fiber cabling—Primarily used for indoor applications, interconnecting remote transceivers, up to ≈500 m (1640 ft), back to the BTS. Indoor systems that utilize multimode optical fiber cabling are designed around 50 μm optical fiber cabling.

Question 39

A(n) _____ wireless local area network (WLAN) is enabled when two or more stations equipped with wireless network interface cards (NICs) communicate with each other.

a. Extended service set (ESS)
b. Basic service set (BSS)
c. Independent basic service set (IBSS)

Answer 39

c. Independent basic service set (IBSS)

p 16-69

An IBSS WLAN is enabled when two or more stations equipped with wireless NICs communicate with each other. An IBSS is intended to serve a small number of devices in a common area (e.g., meeting room), typically for a limited length of time.

Question 40

In distributed antenna system (DAS) design, the term link budget is also called operating:

a. Output
b. Gain
c. Loss
d. Margin

Answer 40

d. Margin

p 16-59

The term link budget also is called operating margin. It refers to the sum of ICT gains and losses, beginning with the transmitter and continuing to the receiver, including transmission line loss and antenna gains.

Question 41

When designing a radiating cable distributed antenna system (DAS), separate cable runs should be used for transmit and receive signals for applications using frequencies below:

a. 900 MHz
b. 800 MHz
c. 500 MHz
d. 400 MHz

Answer 41

d. 400 MHz

p 16-44

Care shall be taken to ensure that radiating cabling is properly polarized for the application for which it is intended. Changing the polarization of the cable run can cause distortion and loss of the signal. In applications below 400 MHz, separate cable runs should be used for
transmit and receive signals to avoid undesired signal coupling.

Question 42

Intermodulation interference occurs when two or more strong signals pass through a _____ device and multiply by each other.

a. Linear
b. Nonlinear

Answer 42

b. Nonlinear

p 16-20

Antennas in close proximity can cause intermodulation that will interfere with other systems. Intermodulation distortion occurs when two or more strong signals pass
through a nonlinear device and multiply by each other.

Question 43

Radiating coaxial cabling antennas offer wide bandwidth for combined systems, with operating frequencies ranging from _____ to more than _____.

a. 70 MHz; 5 GHz
b. 70 MHz; 2.4 GHz
c. 50 MHz; 5 GHz
d. 50 MHz; 2.4 GHz

Answer 43

b. 70 MHz; 2.4 GHz

p 16-43

Radiating cabling is useful in combined systems because of its wide bandwidth, allowing operation from 70 MHz to more than 2.4 GHz (with some limitations).

Question 44

A radio frequency line of sight (RF LoS) _____ a visual line of sight (LoS).

a. Always has
b. May not include

Answer 44

b. May not include

p 16-7

RF LoS—LoS between the receiving and transmitting antennas. There may not be a visual LoS, but there are no modifications to the EM waves being propagated with the LoS Fresnel zone.

Question 45

Personal area networks (PANs) are used to interconnect devices in a personal operating space, which is typically within a _____ radius around an individual.

a. 10 m (33 ft)
b. 4.6 m (15 ft)
c. 3 m (10 ft)
d. 1 m (3.28 ft)

Answer 45

a. 10 m (33 ft)

p 16-64

PANs are the interconnection of information technology devices within a personal operating space, typically within ≈10 m (33 ft) radius.

Question 46

___ Power over Ethernet (PoE) provides dc voltage to an access point (AP) over the unused pairs in a 4-pair balanced twisted-pair channel for 10/100 Mb/s Ethernet.

a. Hybrid mode
b. Phantom mode
c. Mode A
d. Mode B

Answer 46

d. Mode B

p 16-73

10/100 Mb/s Ethernet signaling uses two pairs in a 4-pair balanced twisted-pair cabling channel, making it possible to provide dc voltage to an AP over the unused pairs, which is called Mode B.

1000 Mb/s (Gigabit) Ethernet uses all four pairs of the cabling and requires PoE Mode A (Phantom Power).

Question 47

Multimode optical fiber cabling used for distributed antenna system (DAS) distribution can interconnect remote transceivers to a base transceiver station (BTS) over a maximum span of:

a. 1000 m (3280 ft)
b. 500 m (1640 ft)
c. 300 m (984 ft)
d. 100 m (328 ft)

Answer 47

b. 500 m (1640 ft)

p 16-41

Multimode optical fiber cabling—Primarily used for indoor applications, interconnecting remote transceivers, up to ≈500 m (1640 ft), back to the BTS

Singlemode optical fiber cabling—Used for both indoor and outdoor applications, interconnecting remote transceivers, up to ≈5 km (3.1 mi), back to the BTS.

Question 48

With radio frequency line of sight (RF LoS) propagation, there may be modifications to the electromagnetic waves being propagated.

a. True
b. False

Answer 48

b. False

p 16-7

RF LoS—LoS between the receiving and transmitting antennas. There may not be a visual LoS, but there are no modifications to the EM waves being propagated with the LoS Fresnel zone.

Question 49

Two common cabling topologies used to implement a distributed antenna system (DAS) with a building are:

a. Bus and hierarchical star
b. Ring and bus
c. Tapped trunk and ring
d. Star and tapped trunk

Answer 49

d. Star and tapped trunk

p 16-54

Two common cabling topologies that serve a DAS within a building structure are:
• Star topology.
• Tapped trunk topology.

Question 50

Midspan powering requires that the equipment will be powered over the _____ the balanced twisted-pair cable.

a. Same wire pairs that are used for data transmission over
b. Unused pairs of

Answer 50

b. Unused pairs of

p 16-36

IEEE 802.3af states two powering methods in use:
• Midspan requires that the equipment will be powered over the unused pairs of the balanced twisted-pair cable.
• Endspan will run the power over the same wire pairs that are used for data transmission.

Question 51

The IEEE 802.15 specification for wireless personal area networks (WPANs) _____ the use of the advanced encryption standard (AES) algorithm.

a. Optionally allows for
b. Requires

Answer 51

b. Requires

p 16-109

Question 52

_____ is the process of altering the amplitude, frequency, or phase of a carrier signal in a measured way, which allows for other signals such as voice, data, and video to be added to it.

a. Sampling
b. Conversion
c. Multiplexing
d. Modulation

Answer 52

d. Modulation

p 16-14

Modulation is the process of altering the amplitude, frequency, or phase of a carrier signal in a m

Question 53

In wireless transmission, multi-path fading results in RF signals reaching the receiving antenna by two or more paths. One possible outcome of multi-path fading is an
increase of signal strength, which is known as:

a. Upfade
b. Downfade
c. Nulling
d. Data corruption

Answer 53

a. Upfade

p 16-13

The possible outcomes of multipath are:
• Intersymbol interference, known as data corruption.
• A cancellation of signal, known as nulling.
• A decrease of signal strength, known as downfade.
• An increase of signal strength, known as upfade.

Question 54

In wireless transmission, _____ division duplex transceivers are also referred to as full-duplex devices, capable of simultaneous transmission and reception.

a. Phase
b. Pulse
c. Time
d. Frequency

Answer 54

d. Frequency

p 16-28 Table 16.2

Used for repeaters, PTP links, duplex, two-way radio, and cellular telephone systems. This is also called full-duplex.

Question 55

Which device uses circulators or diplexer filters to separate and combine the different transmit and receive RF paths?

a. Transceiver
b. Bidirectional amplifier
c. Unidirectional amplifier
d. Repeater

Answer 55

b. Bidirectional amplifier

p 16-47

Bidirectional amplifier contain two amplifiers oriented in opposite directions with inputs and outputs combined and steered by directional elements, generally either
circulators or diplexer filters

Question 56

Which device supplies the radio signal into a DAS?

a. Amplifier
b. Receiver
c. Transmitter
d. Transceiver

Answer 56

a. Amplifier

p 16-47

In the DAS environment, amplifiers are used to couple input signals of donor systems and amplify them in the host system for rebroadcast to antennas within the DAS.

Question 57

What device is used in both wired and wireless networks to link network access devices?

a. Bridge
b. Gateway
c. Router
d. Switch

Answer 57

a. Bridge

p 16-74

Bridges are used in both cabled and wireless network environments to link network access devices (e.g., hubs, APs) and extend the physical span or coverage zone of a network.

Question 58

A tapped trunk topology uses _____ cabling to support a DAS.

a. Shielded twisted pair
b. Balanced twisted pair
c. Unbalanced twisted pair
d. Optical fiber

Answer 58

d. Optical fiber

p 16-55

A tapped trunk system may utilize coaxial or optical fiber cabling.

Question 59

In order to maximize its ability to send and receive, an antenna should be _____ to the desired frequency.

a. Dipped
b. Loaded
c. Tuned
d. Peaked

Answer 59

c. Tuned

p 16-42

An antenna shall be tuned (matched) to the same frequency band as the radio system to which it is connected; otherwise, the reception and transmission will be impaired.

Question 60

You are working with the local city hall to develop a public safety wireless network that will be secured from interference and have the capability of delivering up 10 Mbps subscriber speed. What microwave frequency should be used to best meet these needs?

a. 2.4 Ghz
b. 4.9 Ghz
c. 5.0 Ghz
d. 5.3 Ghz

Answer 60

c. 5.0 Ghz

p 16-25

Question 61

Which of the following is NOT a primary method of transporting radio signals in an active DAS?

a. Analog modulation of the RF signal
b. Down conversion of the RF signal
c. Up conversion of the RF signal
d. Digital sampling of the RF signal

Answer 61

c. Up conversion of the RF signal

p 16-52

Active DAS use three primary means to transport radio signals:
• Analog modulation of RF signals onto an optical carrier
• Down conversion of RF signals to IF
• Digital sampling of RF signals