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CompTIA A+ 1101 (Core 1)_ > 2.3 Compare & contrast protocols for wireless networking > Flashcards

2.3 Compare & contrast protocols for wireless networking Flashcards

1
Q

2 main RF bands used by 802.11 standards?

A
  • 2.4GHz
  • 5GHz
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2
Q

What benefit does 2.4GHz RF band have over 5GHz?

A

Better signal penetration, giving it longer signal range

Signal penetration = ability of a signal to pass through obstacles like walls, floors, or building

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3
Q

3 Downsides to 2.4GHz RF band?

A
  • Limited channels
  • Prone to congestion & interference
  • Lower max data rates than 5GHz
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4
Q

3 examples of wireless technologies that congest the 2.4GHz RF band?

A
  • Wi-Fi networks
  • Bluetooth
  • Microwaves

Along with many others

You’ll likely need to memorize these specific examples for the exam

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5
Q

Downside of 5GHz RF band compared to 2.4GHz?

A

Worse signal penetration, giving it less signal range

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6
Q

What is the tradeoff with 5GHz?

A

Supports higher data rates at shorter ranges

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7
Q

Why does 5GHz have higher data rates than 2.4GHz?

A

Supports more individual channels & is less congested

less congestion = less interference

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8
Q

Nominal indoor range for Wi-Fi over 2.4GHz?

A

45m (150 feet)

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9
Q

Nominal indoor range for Wi-Fi over 5GHz?

A

30m (100 feet)

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10
Q

At what distances are clients able to connect to Wi-Fi at full speed?

This applies to both 2.4GHz & 5GHz

A

At 1/3 to a 1/2 of a RF’s max range

This depends on the wireless standard, building features, and interference from other radio sources.

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11
Q

6 IEEE 802.11 standards?

A
  • a
  • b
  • g
  • n
  • ac (Wi-Fi 5)
  • ax (Wi-Fi 6)
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12
Q

What RF band does 802.11a use?

A

5GHz

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13
Q

Data rate of 802.11a?

A

Up to 54Mbps

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14
Q

How many non-overlapping channels does 5GHz RF band have?

A

23

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15
Q

How wide is each channel in 5GHz RF band?

A

20MHz

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16
Q

What do regulatory requirements dictate for the use of 5GHz?

A
  • Channels permitted for Wi-Fi & other purposes
  • Power output of Wi-Fi devices operating in the band

The limites on power output may impace the range of Wi-Fi devices

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17
Q

Why must devices in the 5GHz RF band implement DFS?

DFS = Dynamic Frequency Selection

DFS is a mechanism & is a regulatory requirement in many countries for Wi-Fi devices operating in 5GHz & other certain RF bands

A

It requires Wi-Fi devices to detect & avoid using frequencies used by radar systems

This ensures Wi-Fi coexistence with critical communication systems.

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18
Q

When does a Wi-Fi device with DFS disable a Wi-Fi channel?

A

If it detects radar signals on that channel

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19
Q

What RF band does 802.11b use?

A

2.4GHz

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20
Q

Data rate of 802.11b?

A

Up to 11Mbps

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21
Q

How many channels does 2.4GHz RF band have?

A

14 channels

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22
Q

How are each channels in the 2.4GHz RF band spaced at?

A

5MHz

Meaning each channel would be 5MHz higher in frequency than the previous one (it starts from a base frequency of 2,412MHz , so the next channel would be at 2,417MHz, & so on)

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23
Q

What is the 2.4GHz RF band’s frequency range?

A

2,412-2,484MHz

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24
Q

Why do 802.11b channels overlap quite considerabely?

A

Spacing is only 5MHz & Wi-Fi needs 20MHz channel bandwidth

If you use Channel 2 (2,417MHz to 2,437MHz) in the 2.4GHz band, it overlaps with both Channel 1 (2,412MHz to 2,432MHz) and Channel 3 (2,422MHz to 2,442MHz). Interference can occur if nearby Wi-Fi networks are on Channels 1 or 3.

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25
Q

Which channels in the 2.4GHz RF band has the least overlap?

A

1, 6, & 11

These will suffer the least with interference

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26
Q

What 2.4GHz RF brand channels are permitted in the Americas?

A

1-11

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27
Q

What 2.4GHz RF band channels are permitted in Europe?

A

1-13

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28
Q

What 2.4GHz RF band channels are permitted in Japan?

A

14 (All channels)

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29
Q

What RF band does 802.11g use?

A

2.4GHz

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30
Q

Data rate of 802.11g?

A

Up to 54Mbps

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31
Q

What RF band does 802.11n use?

A

2.4GHz & 5GHz

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32
Q

How is each RF band in 802.11n (2.4 & 5GHz) implemented?

A

By 2 distinct radio transceivers

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33
Q

When is an AP or adapter considered “dual-band”

A

When it can support simultaneous 2.4GHz & 5GHz operations

Cheaper client adapters & many smartphone adapters support only a 2.4GHz radio

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34
Q

Which 802.11 standard introduced channel bonding?

Channel bonding allows more data to be transmitted at once, potentially increasing the overall throughput of the Wi-Fi network

A

802.11n

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35
Q

How does channel bonding in 802.11n work?

Channel bonding allows more data to be transmitted at once, potentially increasing the overall throughput of the Wi-Fi network

A

Combining 2 adjacent 20MHz channels into a single 40MHz channel

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36
Q

Which RF band is better suited for channel bonding?

A

5GHz

2.4GHz should not be used for channel bonding due to its restricted channel layout

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37
Q

Which 802.11 standard introduced MIMO?

MIMO = Multiple Input Multiple Output

A

802.11n

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38
Q

What does MIMO do?

MIMO = Multiple Input Multiple Output

A

Increases reliability & bandwidth by merging signal streams from 2-3 antennas

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39
Q

3 common MIMO notations?

A
  • 1x1
  • 2x2
  • 3x3
40
Q

What do MIMO notations describe?

A

The number of transmit & receive anteannas

1x1 means there is 1 transmit antenna & 1 receive antenna
3x3 means there are 3 transmit antennas & 3 receive antennas

41
Q

Data rate of 802.11n?

A

Up to 72Mbps per stream or 150Mbps per stream for a 40MHz bonded channel

42
Q

What naming convention is used to market 802.11n APs?

A

Nxxx

The N represents 802.11n

i.e. N600

43
Q

What does xxx signify in the 802.11 AP naming convention?

i.e. Nxxx, ACxxx, AXxxx

A

Combined throughput of all radios

44
Q

What does it mean if an 802.11n AP is marketed as an N600 2x2?

A

It can allocate a bonded channel & 2 streams for a data rate of 300Mbps

If it does this simultaneously on both its 2.4GHz & 5GHz radios, the bandwidth of the AP could be described as 600Mbps

45
Q

What is 802.11n aka?

46
Q

What is 802.11ac aka?

47
Q

What is 802.11ax aka?

48
Q

What RF band does 802.11ac (Wi-Fi 5) use?

49
Q

How many radios does a tri band AP have?

A

1 2.4GHz radio & 2 5GHz radios

50
Q

How many streams does 802.11ac (Wi-Fi 5) support?

A

Up to 8 streams

51
Q

What MIMO notation do most 802.11ac (Wi-Fi 5) APs support?

A

4x4 streams

(or lower). Most APs dont support the amount of streams that Wi-Fi 5 can support (Wi-Fi 5 supports up to 8 streams)

52
Q

Data rate for Wi-Fi 5 (802.11ac) with a single stream over an 80MHz channel?

A

Up to 433Mbps

53
Q

What are the bonded channel options for Wi-Fi 5?

A

80 & 160MHz

You can bond 2 adjacent 40MHz channels for an 80MHz channel, or 4 adjacent 40MHz channels for a 160MHz channel. However, not all devices or environments may support or benefit from 160MHz channels due to interference and compatibility issues.

54
Q

What does it mean when 802.11 operations have shared bandwidth?

A

APs can only communicate with 1 station (device) at a time

Multiple station requests go into a queue (just like a hub)

55
Q

What 802.11 standard introduced MU-MIMO?

MU-MIMO = MultiUser MIMO (Multiple Input Multiple Output)

A

802.11ac (Wi-Fi 5)

56
Q

How does DL MU-MIMO partially address the problem of shared bandwidth?

DL MU-MIMO = DownLink MultiUser MIMO (Multiple Input Multiple Output)

A

Allows AP to send data to up to 4 clients simultaneously using multiple antennas

57
Q

Data rate for 802.11ax (Wi-Fi 6) over an 80MHz channel?

A

Up to 600Mbps

58
Q

What RF band does 802.11ax use?

A

2.4 & 5GHz

59
Q

How does Wi-Fi 6e differ from Wi-Fi 6?

A

Adding support for 6GHz RF band

60
Q

What is the tradeoff with Wi-Fi 6e’s 6GHz RF band?

A

Has less range but more frequency space

This makes it easier to use 80 & 160 MHz channels

61
Q

How many clients can Wi-Fi 5 (802.11ac) serve simultaneously?

A

Up to 4

(using MU-MIMO in the downlink direction)

62
Q

How many clients can Wi-Fi 6 (802.11ax) serve simultaneously?

63
Q

Which 802.11 standard adds support for uplink MU-MIMO?

A

802.11ax (Wi-Fi 6)

64
Q

What does uplink MU-MIMO do?

A

Allows MU-MIMO-capable clients to send data to the AP simultaneously

65
Q

Which 802.11 standard introduced OFDMA?

Orthogonal Frequency Division Multiple Access

A

802.11ax (Wi-Fi 6)

66
Q

Why does 802.11ax use MU-MIMO & OFDMA?

(MU-MIMO = Multiuser Multiple Input Multiple Output)
(OFDMA = Orthogonal Frequency Division Multiple Access)

A

To improve client density

This means sustatining high data rates when more stations are connected to the same AP

67
Q

Meaning of SSID?

A

Service Set Identifier

68
Q

How long can SSIDs be?

69
Q

What ASCII characters should be used for SSIDs?

A
  • Numbers
  • Letters
  • + (Plus)
  • - (Minus)
  • _ (Underscore)

These should be used to avoid compatibility issues

70
Q

What happens if the same SSID is used for both RF bands in AP configuration?

A

The AP and client device search for the band with the strongest signal

71
Q

What happens if different names are configured for both RF bands in AP configuration?

(2.4GHz & 5GHz)

A

User can choose which network & band to use

72
Q

What is long-range fixed wireless?

A

Wireless technology commonly used to bridge 2 networks

73
Q

How does P2P LoS fixed wireless create a direct link between 2 locations?

(P2P = Point to Point) (LoS = Line of Sight)

This is a specific type of fixed wireless communications

A

Using precisely aligned high-gain microwave antennas

“high-gain” means the antenna is strongly directional

74
Q

What is the max range for a P2P LoS fixed wireless link?

WITHOUT OBSTRUCTION BY PHYSICAL OBJECTS!

75
Q

Where are antennas in a P2P LoS fixed wireless link typically placed?

A

Top of tall building/poll

This reduces the risk from obstructions

76
Q

How can long-range fixed wireless be implemented?

A

Using licensed or unlicened frequency spectrum

77
Q

What does a Licensed frequency spectrum mean?

A

Network operator buys exclusive RF band rights from regulator

Network operator means entity/org managing a telecom network. i.e. ISP

The US regulator is the Federal Communications Commision (FCC). If any interferense sources are discovered, the network operator has the legal right to get them shut down

78
Q

What does an Unlicensed frequency spectrum mean?

A

Operator uses a public RF band

Network operator means entity/org managing a telecom network. i.e. ISP

79
Q

What must operators adhere to when operating in unlicensed spectrum?

A

Regulatroy power limitations

80
Q

Data rate of bluetooth?

A

Up to 3Mbps

Depending on Bluetooth version

81
Q

What speeds can Bluetooth adapters supporting version 3 or 4 achieve?

A

Up to 24Mbps

82
Q

How do Bluetooth adapters supporting version 3/4 achieve a 24Mbps data rate?

A

They can negotiate an 802.11 radio link for large file transfers

83
Q

What variant did Bluetooth 4 introduce?

A

Bluetooth Low Energy (BLE)

84
Q

What is Bluetooth Low Energy (BLE) designed for?

A

Small low-power devices transmitting small data infrequently

i.e. Fitness trackers, smart locks, asset tracking tags, etc.

85
Q

is BLE backwards compatible with “classic” Bluetooth?

BLE = Bluetooth Low Energy

86
Q

Can a device support Bluetooth & BLE simultaneously?

BLE = Bluetooth Low Energy

87
Q

Meaning of RFID?

A

Radio Frequency ID

88
Q

What is RFID?

A

Means of identifying & tracking objects using encoded tags

89
Q

What happens when a RFID reader scans a tag?

A

Tag responds with the information programmed into it

90
Q

What does it mean when an RFID tag is passive?

A

It only responds when scanned at close range

Up to about 25m

91
Q

How far can an active RFID tag be read from?

(powered)

A

100m (328 feet)

92
Q

What type of RFID tags can be embedded in stickers/labels?

A

Passive RFID tags

RFID is also used to implement some types of access badge to operate electronic locks

93
Q

Meaning of NFC?

A

Near-Field Communication

94
Q

What does it mean that NFC is a P2P version of RFID?

A

NFC devices can function as tags & as readers

Allowing them to exchange data with other NFC-enabled devices

95
Q

What are the data rates of NFC?

A
  • 106 Kbps
  • 212 Kbps
  • 424 Kbps

CompTIA A+ 1101 (Core 1)_ (28 decks)

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