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DB > TDMM Chapter 16 > Flashcards

TDMM Chapter 16 Flashcards

1
Q

Absorption

A

The loss of energy in an electromagnetic signal as it passes through a medium

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2
Q

AGC

A

Automatic Gain Control

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3
Q

Amplitude

A

The size or magnitude of a waveform

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4
Q

Access Point (AP)

A

Standalone hardware device that acts as a wireless communications hub

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5
Q

BSS

A

Basic Service Set
A single wireless LAN and its associated clients

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6
Q

DAS

A

Distributed Antenna System

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7
Q

Diffraction

A

The bending of sound, radio or light waves around an object

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8
Q

Dispersion

A

The loss incurred by an RF signal due to the natural broadening of the wave front

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9
Q

ERRCS

A

Emergency Responder Radio Coverage Systems

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10
Q

Extended Service Set (ESS)

A

A collection of access points tied together by a wired backbone

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11
Q

Frequency

A

The number of cycles or events per unit of time

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12
Q

Independent Basic Service Set (IBSS)

A

A group of stations within a wireless LAN that communicate without a central access point

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13
Q

IR (Standard)

A

Infrared (Standard)
A communications system built on the IR light spectrum

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14
Q

LoS

A

Line of Signt

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15
Q

NIC

A

Network Interface Card

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16
Q

OS

A

Operating System

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17
Q

PTP

A

Point to Point
A direct connection established between two points

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18
Q

Reflection

A

The abrupt change in direction of a wave at a dissimilar media, such that the wave returns into the original media

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19
Q

Refraction

A

The abrupt change in direction of a wave at a dissimilar media, such that the wave enters the second medium

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20
Q

QoS

A

Quality of Service

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21
Q

Scattering

A

A change in direction/frequency of a wave when it encounters particles sized similar to the wavelength

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22
Q

Wavelength

A

The distance between points of a phase of one complete cycle of wave

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23
Q

WLAN

A

Wireless Local Access Network

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24
Q

Name three technological considerations in wireless design

A
  • Scalability of the network
  • Compatibility of the overall network
  • Implementation of a wireless network based around standards
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25
Q

Name three factors that define the reliability of a wireless network

A
  • Accessibility
  • Continuity
  • Consistency of Service
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26
Q

Name four factors that affect the throughput of a wireless network

A
  • Application requirements
  • Number of users
  • Future requirements
  • Capabilities of the products used
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27
Q

What type of impact do radio communications towers have on the footprint of a facility?

A

They have a limited footprint

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28
Q

Name three reasons the roof top of a tall building may be an unsuitable location for a cellular system

A
  • Difficult to get signal to street level
  • Increased potential for interference
  • Reduces frequency reuse capabilities
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29
Q

Name three methods for evaluating the environment in which a wireless network will be used

A
  • Site survey
  • Propagation analysis
  • Modeling
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30
Q

What two considerations does a QoS program attempt to balance?

A
  • End user expectations
  • Wireless network performance
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31
Q

What term is used to describe the number of cycles or events per unit of time?

A

Frequency

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32
Q

What unit of measure is used to express the frequency of an electromagnetic signal?

A

Herts (Hz)

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33
Q

What does one hertz equal?

A

One cycle per second

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34
Q

What term is used to describe the distance between two points of a corresponding phase of one complete cycle of a wave?

A

Wavelength

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35
Q

What unit of measure is typically used for wavelengths in an electromagnetic system?

A

Meters

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36
Q

What term is used to describe the motion of waves through or along a medium?

A

Propagation

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37
Q

Define line of sight in terms of propagation

A

A propagation in which the radiation from the transmitter to the receiver is unobstructed

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38
Q

Name two types of LoS propagation

A
  • Visual
  • Radio Frequency (RFI)
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39
Q

What is visual LoS?

A

The visual observation of one point to another as seen by the observers eye

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40
Q

What is RF LoS?

A

The line of sight between the receiving and transmitting antennas

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41
Q

What are Fresnel zones?

A

A series of concentric ellipsoids surrounding the path

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42
Q

How is the first Fresnel Zone used?

A

As a nominal unit to measure certain distances in terms of their effects on frequency

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43
Q

What is the minimum clearance requirement for reliable wireless service?
(expressed in fresnel zones)

A

60 percent of F1 clearance

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44
Q

Name two categories of barriers and obstructions that impede electromagnetic waves

A
  • Natural
  • Man made
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45
Q

What is free space loss?

A

The signal attenuation that would result if all reflection, scattering, diffraction and absorption influences were removed

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46
Q

What term refers to the abrupt change i. direction of a wave at the interface between two dissimilar media such that the wave returns into the medium from which it originated?

A

Reflection

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47
Q

What term refers to the abrupt change i. direction of a wave at the interface between two dissimilar media such that the wave enters the second medium?

A

Refraction

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48
Q

What term describes the change in frequency/direction of the wave when it encounters small particles

A

Scattering

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49
Q

What term is used to describe the bending of light around an object?

A

Diffraction

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50
Q

What term is used to describe the loss of energy in an electromagnetic signal as it passes through a medium?

A

Absorption

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51
Q

What is a sky wave?

A

A sky wave is a wave that is usable due to reflection and refraction in the ionosphere

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52
Q

What is the ionosphere?

A

The portion of earths upper atmosphere where ions and electrons are present in quantities sufficient to affect the propagation of radio waves

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53
Q

Normally the ionosphere extends to ?

A

30 miles to 621 miles above the earth

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54
Q

What causes the distance to the radio horizon to exceed the optical horizon within the troposphere?

A

Within the troposphere bending of radio waves by refraction makes the distance to the radio horizon exceed the distance to the optical horizon

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55
Q

At what distance does tropospheric refraction typically affect received signals?

A

At distances beyond the radio horizon

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56
Q

What is a direct wave?

A

An RF wave that travels directly from the transmitting antenna to the receiving antenna

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57
Q

How can the LoS distance be extended in terrestrial communications?

A

By increasing the height of the transmitting antenna or receiving antenna

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58
Q

What is a ground wave?

A

A wave that travels along the surface

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59
Q

What is the maximum range of a surface path when high powered transmitters and efficient antennas are used?

A

310 miles

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60
Q

What is the relationship between the range of a surface path and frequency?

A

The surface path range decreases as frequency increases

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61
Q

What is isotropic gain?

A

The ratio of actual signal strength at the antenna relative to an ideal isotropic radiator

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62
Q

What is fading?

A

The variation of the amplitude of part of a signal

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63
Q

Name the two types of fading

A
  • Multipath fading
  • Delay spread
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64
Q

What is modulation

A

The process of altering the carrier signal

65
Q

Name four types of modulation

A
  • Amplitude modulation
  • Frequency modulation
  • Phase modulation
  • Pulse modulation
66
Q

What is amplitude modulation

A

superimposing a signal on a carrier wave

67
Q

What is frequency modulation?

A

Superimposing a signal on an RF carrier wave

68
Q

What is phase modulation?

A

The method of superimposing a signal on a carrier wave

69
Q

What is pulse modulation?

A

The method of superimposing a series of pulses carrying the signal on a carrier wave

70
Q

Which modulation technique uses two different phase angles that are usually out of phase by 180 degrees?

A

Binary Phase Shift Keying (BPSK)

71
Q

Which modulation technique uses four different phase angles that are usually out of phase by 90 degrees?

A

Quadrature phase shift keying (QPSK)

72
Q

What is complementary code keying (CCK)?

A

The basis for high rate physical layer extension to deliver data rates of 11 mb/s

73
Q

Describe how the QAM modulation technique works

A

Two carriers at the same frequency are independantly amplitude modulated and combined for transmission

74
Q

Describe how the OFDM modulation technique works

A

A large number of closely spaced orthogonal sub carriers are combined into parallel streams

75
Q

How does the OFDMA modulation technique achieve a more efficient use of airtime?

A

By scheduling the transmissions from the clients so they do not clash with each other

76
Q

What are harmonics

A

The multiples of an alternating currents fundamental frequency

77
Q

What is the first harmonic?

A

The fundamental frequency

78
Q

What is the second harmonic?

A

Twice the functional frequency

79
Q

What is harmonic distortion?

A

The presence of unwanted harmonic frequencies

80
Q

Name four types of harmonic filters

A
  • high pass filter
  • low pass filter
  • band pass filter
  • band stop filter
81
Q

What term describes an increase in an RF signals power?

A

Gain

82
Q

Name two sources of gain

A
  • External power sources
  • Passive sources
83
Q

What term describes a decrease in signal strength?

A

Loss

84
Q

Name the two main sources of loss in a wireless system

A
  • Impedance of cables and connectors
  • Absorption, reflection, refraction, scattering or destruction during propagation
85
Q

What unit provides an absolute measurement of power?

A

Watt

86
Q

What unit provides a measurement of the relative gain or loss of power?

A

Decibel

87
Q

What rule is commonly used to calculate isotrpic gain for antennas?

A

The 6dB rule

88
Q

Name eight types of information that should be gathered before the wireless network is required?

A
  • Bandwidth requirement
  • Number of uses
  • Growth and expandability
  • Existing data network
  • User environment
  • EM and RF noise
  • Building Construction
  • Climate
89
Q

Name the two primary types of wireless networks

A
  • Licensed
  • Unlicensed
90
Q

What is the frequency range for PTP licensed wireless networks?

A

6 GHz to 40 GHz

91
Q

What frequencies are used primarily for public safety applications?

A

6 GHz to 11 GHz

92
Q

What frequencies are primarily used in the private sector for PTP applications?

A

18 GHz and above

93
Q

What frequencies are the most prevalent for wireless deployments for the unlicensed spectrum?

A

2.4GHz and 5 GHz

94
Q

What frequency range is used by amateur radio operators?

A

2.4 GHz and below

95
Q

How does licensing provide a higher level of interference protection that what is found in unlicensed systems?

A

By limiting the use of any frequency to a single user in any one area

96
Q

What is path loss?

A

The loss of the RF signal power from its originating point to the ultimate end point

97
Q

Name five factors that contribute to path loss

A
  • Frequency of RF signal
  • Transmission power
  • Distance between the transmit and receive antenna
  • Obstructions
  • Terrain
98
Q

Name five factors used to select the proper antenna for an application

A
  • Required gain
  • Allowable wind load
  • Frequency
  • Aesthetics
  • Zoning
99
Q

What is the purpose of a radome cover for a parabolic antenna?

A

To keep ice and snow off

100
Q

How does a radome cover affect an RF signal?

A

It causes some loss

101
Q

What is the common path loss when using radome covers?

A

0.5 dB isotropic

102
Q

Name two problems associated with oversizing antennas

A
  • Interference
  • Damage to radio equipment
103
Q

Name the two basic measurements used in analyzing radio waves and other wave forms

A
  • Frequency
  • Amplitude
104
Q

Name the three categories of wireless tranceivers

A
  • Half duplex
  • Frequency division duplex
  • Time division duplex
105
Q

What type of transceiver is incapable of transmitting and receiving signals at the same time?

A

Half Duplex

106
Q

How does a frequency division duplex transceiver operate?

A

Transmits and receives simultaneously

107
Q

How does a time division duplex transceiver operate?

A

Transmits and receives at RF alternately in sequential time slots

108
Q

Define Antenna

A

A means for coupling RF energy from a transmission onto a transmission medium

109
Q

What will happen if the wrong connector is used in an antenna system?

A

Will cause degredation

110
Q

Name five considerations for implementing an outdoor PTP solution

A
  • Distance
  • Terrain
  • Climate
  • Physical obstructions
  • Cabling attenuation
111
Q

What is a jinpole?

A

A rigging tool that is used to hoist sections up a tower

112
Q

What is the benefit of using jumpers to connect the RF media to the antenna and the equipment?

A

Allows system to be serviced without damaging other parts

113
Q

What is the weakest part of an antenna system?

A

The antenna connector

114
Q

What is the purpose of a voltage injector?

A

To power electronic equipment located away from a convenient power source

115
Q

Name two major types of voltage injectors

A
  • Coaxial
  • PoE
116
Q

How far above the roof should RF media be supported?

A

At least 1.5 in

117
Q

What is a distributed antenna system?

A

A system that transmits signals where outdoor network signals cant penetrate

118
Q

Name seven components of a DAS

A
  • Transmitter
  • Receiver
  • Amplifier
  • Converter
  • Cabling
  • Connector
  • Antenna
119
Q

Name five types of cable that are commonly recognized for DAS cabling distribution

A
  • SM Fiber
  • MM Fiber
  • Hybrid fiber
  • Twisted pair
  • Coaxial cable
120
Q

What category of twisted pair is recommended for DAS cabling distribution?

A

Category 6A

121
Q

Excluding the base station hardware, what is the most expensive part of a DAS?

A

The antenna network

122
Q

Name four types of Antennas used in a DAS?

A
  • Omnidirectional
  • Directional
  • Radiating cable
  • Combination of all three
123
Q

What type of antenna broadcasts equally in all directions of one cross section of its toroidal radiation pattern?

A

Omnidirectional

124
Q

What type of antenna concentrates the radiated signal in one direction more than in another?

A

Directional

125
Q

Why is a radiating coaxial cabling useful in combined systems?

A

It has a wide bandwidth, from 70 MHz to 2.4 GHz

126
Q

True or False
A radiating cable should be placed in a metal conduit for protection?

A

False

127
Q

Name five common types of active DAS equipment

A
  • Transceiver
  • Bidirectional amplifiers
  • Unidirectional amplifiers
  • Repeaters
  • Power supply units
128
Q

What is a transceiver?

A

A device that uses many of its components to transmit and receive RF signals

129
Q

What function is typically performed by the power supply unit?

A

Converts AC to DC

130
Q

What is the primary headend device?

A

Master Control Unit (MCU)

131
Q

Name three suitable locations for an Master Control Unit (MCU)

A
  • Main Equipment Room
  • Telecom Room
  • Penthouse near roof
132
Q

Where is DAS backend equipment typically located?

A

In the TR

133
Q

Name the three primary means used by active DAS to transport radio signals

A
  • Analog modulation
  • Down conversion
  • Digital sampling of RF signals
134
Q

What is an advantage of analog modulation?

A

The ability to modulate a large portion of the radio spectrum over one optical path

135
Q

What is a major problem associated with analog systems?

A

The direct dependency of the modulation and recovery of the RF signal to the optical transport

136
Q

What is the primary medium used for DAS analog systems?

A

Singlemode optical fiber

137
Q

How do DAS analog systems compensate for the dependency on optical losses?

A

By using automatic gain control (AGC) as a feedback loop

138
Q

How is passive distribution equipment in a DAS defined?

A

As equipment that does not require external power input

139
Q

What is a directional coupler?

A

A device that splits power from one input connector to two or more output connectors

140
Q

What piece of passive DAS equipment combines dc power with the ac RF signals on a coaxial cable and taps it off at the other end?

A

Bias Tee

141
Q

What piece of passive DAS equipment is used to combine two wireless bands to a single antenna feed or distribution cable?

A

Hybrid coupler

142
Q

Which piece of passive DAS equipment accepts an input signal and delivers multiple output signals with specific phase and amplitude characteristics?

A

Power Splitter

143
Q

Name three characteristics of output signals in power splitters

A
  • Equal amplitude
  • Zero degree phase relationship between any two output signals
  • High isolation between each output signal
144
Q

Name two common topologies that serve a DAS within a building structure

A
  • Star topology
  • Tapped trunk topology
145
Q

Name three factors that may affect the selection of a cabling topology for a DAS

A
  • DAS equipment
  • Cabling medium used in a new installation
  • Legacy cabling system
146
Q

What cabling mediums may be used in the installation of a star topology?

A
  • Twisted pair
  • Coaxial
  • Fiber
  • Combination
147
Q

What types of cabling may be used to install a tapped trunk topology?

A
  • Coaxial
  • Fiber
148
Q

What component is used to tap into the coaxial cable of a tapped trunk topology?

A

Splitter or vampire tap

149
Q

Name two potential problems associated with using a DAS to support mobile communications in buildings

A
  • Availability of RF signals
  • Ability to support required capacity
150
Q

Name the three phases associated with DAS design

A
  • Pre Installation
  • Installation
  • Acceptance
151
Q

What is the purpose of conducting RF measurements during an on site survey of the radio environment?

A

To identify existing signals and their frequency strength

152
Q

Name two factors that determine the overall usability and capability of an installed DAS

A
  • Selection
  • Location
153
Q

What is the link budget (operating margin)

A

The sum of ICT gains and losses in an ITS

154
Q

What is a personal Area Network (PAN)

A

The interconnection of information technology devices within a personal operating space

155
Q

What is the typical radius of a PAN?

A

10 m (33 ft)

156
Q

Name three key factors for a PAN

A
  • Lower power consumption
  • Low cost
  • Superior ease of use
157
Q

True or False
IS is unaffected by RF

A

True

158
Q

What is the intended purpose of a public WLAN or hotspot?

A

To provide convenient access to internet based information

159
Q

Name three categories of WLAN services based on access restrictions

A
  • Unrestricted access
  • Established account acces
  • Temporary account access

DB (19 decks)

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