Certified Wireless Network Professional (CWNA) Quiz

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1/70 Questions

What can cause an excessively high VSWR (Voltage Standing Wave Ratio) in a WLAN RFtransmission line?
- Reflected direct current (DC) voltage on the main RF signal line
- An impedance mismatch in the RF cables and connectors
- Attenuation of the RF signal as it travels along the main signal path
- Crosstalk (inductance) between adjacent RF conductors

About This Quiz

This Certified Wireless Network Professional (CWNA) quiz assesses knowledge on WLAN RF transmission issues such as VSWR and return loss, RF signal behaviors like refraction and propagation, and calculations integral to network planning like Link Budget. It is crucial for professionals aiming to enhance their expertise in wireless networking.

Certified Wireless Network Professional (CWNA) Quiz - Quiz

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2.

What word describes the bending of an RF signal as it passes through a medium of a varyingdensity from that of free space?
- Reflection
- Diffraction
- Refraction
- Diffusion
- Scattering
Correct Answer

A. Refraction

Explanation

Refraction is the correct answer because it refers to the bending of an RF signal as it passes through a medium with a varying density from that of free space. When the signal encounters a change in the density of the medium, such as when it passes from air to water or from one type of material to another, it bends or changes direction. This phenomenon is known as refraction.

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3.

What factors influence the distance that an RF signal can be effectively received? (Choose 3)
- MAC layer encryption
- Transmitting station’s power source
- Free Space Path Loss
- Transmitting station’s output power
- Temperature in the Fresnel zone
- Receiving station’s radio sensitivity
Correct Answer(s)

A. Free Space Path Loss
A. Transmitting station’s output power
A. Receiving station’s radio sensitivity

Explanation

The three factors that influence the distance that an RF signal can be effectively received are Free Space Path Loss, Transmitting station’s output power, and Receiving station’s radio sensitivity. Free Space Path Loss refers to the loss of power as the signal travels through space. The Transmitting station’s output power determines the strength of the signal being transmitted. The Receiving station’s radio sensitivity indicates how well the station can detect and interpret the incoming signal. These factors collectively determine the effective range of an RF signal.

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4.

As an RF wave propagates through space, the wave front experiences natural expansion thatreduces its signal strength in an area. What term describes the rate at which this expansionhappens?
- MU-MIMO
- Inverse square law
- Path spread phenomenon
- Fresnel zone thinning
- Ohm’s law
Correct Answer

A. Inverse square law

Explanation

The term that describes the rate at which the expansion of the wave front happens is the inverse square law. According to this law, the intensity of the wave decreases as the square of the distance from the source increases. This means that as the RF wave propagates through space, the signal strength diminishes rapidly with distance.

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5.

Return Loss is the decrease of forward energy in a system when some of the power is beingreflected back toward the transmitter.What will cause high return loss in an RF transmission system, including the radio, cables,connectors and antenna?
- A Voltage Standing Wave Ratio (VSWR) of 1:1
- Cross-polarization of the RF signal as it passes through the RF system
- An impedance mismatch between components in the RF system
- The use of cables longer than one meter in the RF system
- High output power at the transmitter and use of a low-gain antenna
Correct Answer

A. An impedance mismatch between components in the RF system

Explanation

An impedance mismatch between components in the RF system can cause high return loss in an RF transmission system. When there is a mismatch in impedance between different components, such as the radio, cables, connectors, and antenna, some of the power from the forward energy gets reflected back towards the transmitter, resulting in a high return loss. This can lead to signal degradation and reduced efficiency in the transmission system.

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6.

What factors are taken into account when calculating the Link Budget of a point-to-point outdoorWLAN bridge link?
- Antenna height
- Transmit antenna gain
- Transmit power
- Operating frequency
Correct Answer(s)

A. Transmit antenna gain
A. Transmit power
A. Operating frequency

Explanation

The factors that are taken into account when calculating the Link Budget of a point-to-point outdoor WLAN bridge link are the transmit antenna gain, transmit power, and operating frequency. The transmit antenna gain refers to the ability of the antenna to focus the transmitted signal in a specific direction, which can affect the signal strength and coverage. The transmit power is the amount of power that is being transmitted, which also affects the signal strength. The operating frequency is the frequency at which the wireless communication is taking place, and different frequencies can have different propagation characteristics and signal losses.

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7.

A WLAN transmitter that emits a 200 mW signal is connected to a cable with 3 dB loss.If the cable is connected to an antenna with 10 dBi gain, what is the EIRP at the antenna element?
- 10 dBm
- 13 dBm
- 20 dBm
- 26 dBm
- 30 dBm
Correct Answer

A. 30 dBm

Explanation

The EIRP (Effective Isotropic Radiated Power) is calculated by adding the transmitter power, cable loss, and antenna gain. In this case, the transmitter emits a 200 mW signal (23 dBm), the cable has a 3 dB loss, and the antenna has a 10 dBi gain. Adding these values together, we get 23 dBm - 3 dB + 10 dBi = 30 dBm. Therefore, the EIRP at the antenna element is 30 dBm.

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8.

In a long-distance RF link, what statement about Fade Margin is true?
- The Fade Margin of a long-distance radio link should be equivalent to the receiver’s antenna gain.
- A Fade Margin is unnecessary on a long-distance RF link if more than 80% of the first Fresnel zone is clear of obstructions
- Fade Margin is an additional pad of signal strength designed into the RF system to compensate for unpredictable signal fading.
- The Fade Margin is a measurement of signal loss through free space, and is a function of frequency and distance.
Correct Answer

A. Fade Margin is an additional pad of signal strength designed into the RF system to compensate for unpredictable signal fading.

Explanation

Fade Margin is an additional pad of signal strength that is intentionally added to the RF system. It is designed to compensate for unpredictable signal fading, which can occur due to various factors such as atmospheric conditions, interference, and obstacles in the signal path. By having a higher signal strength than what is actually required for reliable communication, the fade margin ensures that even if the signal weakens temporarily, it will still remain above the minimum threshold for successful transmission. This helps to maintain a reliable and stable long-distance RF link.

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9.

Which unit of measurement is an absolute unit that is used to quantify power levels on a linearscale?
- DBm
- W
- dB
- mW
- VSWR
Correct Answer

A. DBm

Explanation

dBm is the correct answer because it is an absolute unit of measurement used to quantify power levels on a linear scale. It is a logarithmic unit that represents power relative to a reference level of 1 milliwatt (mW). dBm is commonly used in telecommunications and electronics to express power levels in a more convenient and manageable way.

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10.

An 802.11 WLAN transmitter that emits a 50 mW signal is connected to a cable with 3 dB of loss.The cable is connected to an antenna with 16 dBi of gain.What is the EIRP power output?
- 1000 mW
- 25 mW
- 50 mW
- 250 mW
- 10 mW
Correct Answer

A. 1000 mW

Explanation

The EIRP (Effective Isotropic Radiated Power) is calculated by adding the transmitter power output (in this case, 50 mW) with the gain of the antenna (in this case, 16 dBi) and subtracting the loss of the cable (in this case, 3 dB). Converting the gain from dBi to dBd (decibels relative to a dipole), the calculation becomes: EIRP = Transmitter power output + Antenna gain - Cable loss = 50 mW + 16 dBd - 3 dB = 1000 mW. Therefore, the EIRP power output is 1000 mW.

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11.

What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles(5 kilometers)?
- Accurate Earth Bulge calculations
- Minimum output power level of 2 W
- Grid antennas at each endpoint
- A Fresnel Zone that is at least 60% clear of obstructions
- A minimum antenna gain of 11 dBi at both endpoints
Correct Answer

A. A Fresnel Zone that is at least 60% clear of obstructions

Explanation

To establish a high-quality 2.4 GHz RF link at a distance of 3 miles (5 kilometers), it is important to have a Fresnel Zone that is at least 60% clear of obstructions. The Fresnel Zone is an elliptical area around the direct line of sight between the transmitter and receiver. Obstructions within this zone can cause signal degradation and interference. By ensuring that at least 60% of the Fresnel Zone is clear, the RF signal can propagate with minimal interference, resulting in a high-quality link.

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12.

What phrase defines Equivalent Isotropically Radiated Power (EIRP)?
- Reflected power due to an impedance mismatch in the signal path
- The power output from the radio into the RF cable
- The highest RF signal strength that is transmitted from a given antenna
- Power supplied from the transmission line to the antenna input
- The power output from the radio into the RF cable
Correct Answer

A. The highest RF signal strength that is transmitted from a given antenna

Explanation

The phrase "Equivalent Isotropically Radiated Power (EIRP)" refers to the highest RF signal strength that is transmitted from a given antenna.

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13.

What term describes the effect of increasing the intensity of an RF wave with an antenna byfocusing the energy in a specific direction?
- Beam Compression
- Distributed Radiation
- Active Amplification
- Passive Gain
- RF Flooding
Correct Answer

A. Passive Gain

Explanation

Passive Gain describes the effect of increasing the intensity of an RF wave with an antenna by focusing the energy in a specific direction. This term refers to the process of using passive elements such as reflectors or directors to shape the radiation pattern of the antenna, resulting in increased signal strength in the desired direction.

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14.

Which antenna types are commonly used by indoor Wi-Fi devices in a MIMO diversityimplementation? (Choose 2)
- Grid
- Dipole
- Patch
- Dish
- Sector
Correct Answer(s)

A. Dipole
A. Patch

Explanation

Dipole and Patch antennas are commonly used by indoor Wi-Fi devices in a MIMO diversity implementation. Dipole antennas are simple and omnidirectional, meaning they radiate signals in all directions. Patch antennas, on the other hand, are directional and provide a focused signal in a specific direction. Using a combination of these two antenna types allows for improved signal coverage and diversity, which helps to enhance the overall performance and reliability of the Wi-Fi network in indoor environments.

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15.

What phrase correctly completes the following sentence?When using WMM Power Save operation, a wireless client device ______________.
- Alternates between awake and dozing, depending on its need to transmit and receive information
- Enters a low-power radio state until it receives a WMM PS-Poll frame from the AP
- Experiences higher throughput and lower latency than when operating in Active mode
- Powers down a subset of MIMO radio chains and transmits information at a slower data rate
- Buffers frames destined to the low-power AP until the AP wakes its radio and begins beaconing again
Correct Answer

A. Alternates between awake and dozing, depending on its need to transmit and receive information

Explanation

When using WMM Power Save operation, a wireless client device alternates between awake and dozing, depending on its need to transmit and receive information. This means that the device will periodically enter a low-power state (dozing) to conserve energy when it does not have any data to transmit or receive. However, it will wake up (awake) when it needs to send or receive information. This allows the device to save power while still being able to communicate effectively.

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16.

When replacing the antenna of a WLAN device with a similar antenna type that has a higherpassive gain, what antenna characteristic will decrease?
- Range
- Beam width
- Active gain
- Receive sensitivity
- Fresnel Zone size
- Fresnel Zone size
Correct Answer

A. Beam width

Explanation

When replacing the antenna of a WLAN device with a similar antenna type that has a higher passive gain, the beam width will decrease. Beam width refers to the angle between the half-power points of the main lobe in the radiation pattern of the antenna. A higher passive gain means that the antenna focuses more of its energy in a narrower beam, resulting in a smaller beam width. This narrower beam width can lead to a more concentrated signal, but it may also reduce the coverage area or range of the WLAN device.

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17.

What statements about the beamwidth of an RF antenna are true? (Choose 2)
- The lower the gain of an antenna, the more narrow one or both beamwidths become
- The beamwidth patterns on an antenna polar chart indicate the point at which the RF signal stops propagating
- Horizontal and vertical beamwidth are calculated at the points in which the main lobe decreases power by 3 dB.
- Horizontal beamwidth is displayed (in degrees) on the antenna’s Azimuth Chart.
Correct Answer(s)

A. Horizontal and vertical beamwidth are calculated at the points in which the main lobe decreases power by 3 dB.
A. Horizontal beamwidth is displayed (in degrees) on the antenna’s Azimuth Chart.

Explanation

The first statement is true because the gain of an antenna is inversely proportional to the beamwidth. A lower gain antenna will have a narrower beamwidth.

The second statement is also true because the beamwidth patterns on an antenna polar chart indicate the boundaries at which the RF signal stops propagating. These patterns show the extent of the antenna's coverage area.

Therefore, the correct answer is that horizontal and vertical beamwidth are calculated at the points in which the main lobe decreases power by 3 dB, and horizontal beamwidth is displayed (in degrees) on the antenna's Azimuth Chart.

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18.

What HT technology requires MIMO support on both the transmitter and receiver?
- Spatial multiplexing
- Short guard intervals
- Maximal ratio combining
- Orthogonal Frequency Division Multiplexing
Correct Answer

A. Spatial multiplexing

Explanation

Spatial multiplexing is a technology that requires MIMO (Multiple-Input Multiple-Output) support on both the transmitter and receiver. MIMO involves the use of multiple antennas to transmit and receive multiple data streams simultaneously. Spatial multiplexing takes advantage of the multiple antennas to transmit different parts of the data simultaneously, increasing the overall data rate. Therefore, in order to utilize spatial multiplexing, both the transmitter and receiver must support MIMO technology.

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19.

ABC Company has just purchased a 6 dBi patch antenna. After performing some tests with the 6 dBi antenna, they have concluded that more antenna gain is needed to cover their outdoor courtyard. When choosing an antenna with higher gain, what other antenna characteristic will also always change?
- Fresnel Zone size
- Beamwidth
- Maximum input power
- Impedance
- VSWR Ratio
Correct Answer

A. Beamwidth

Explanation

When choosing an antenna with higher gain, the beamwidth will also always change. Beamwidth refers to the angle of coverage of the antenna's main lobe. A higher gain antenna will have a narrower beamwidth, meaning it will focus its energy in a more concentrated direction. This can be beneficial in situations where a specific area needs to be targeted with a stronger signal. However, it also means that the antenna's coverage area will be reduced, as the signal will be less dispersed.

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20.

AP-1 is a 3x3:2 AP. STA-3 is a 3x3:3 client. What is the maximum number of spatial streams thatcan be used for a downlink HT-OFDM transmission from AP-1 to STA-3?
- One spatial stream, because the definition of the AP indicates that it is capable of only one spatial stream.
- Three spatial streams, because the definition of the client indicates that it is capable of only three spatial streams.
- Two spatial streams, because the definition of the AP indicates that it is capable of only two spatial streams
- Three spatial streams, because the definition of the AP indicates that it is capable of only three spatial streams.
Correct Answer

A. Two spatial streams, because the definition of the AP indicates that it is capable of only two spatial streams

Explanation

The correct answer is two spatial streams because the AP-1 is a 3x3:2 AP, which means it has three transmit antennas and two spatial streams. The STA-3 client is a 3x3:3 client, which means it has three transmit antennas and three spatial streams. However, the maximum number of spatial streams that can be used for a downlink HT-OFDM transmission from AP-1 to STA-3 is determined by the capabilities of the AP. Since the AP is capable of only two spatial streams, that is the maximum number that can be used for the transmission.

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21.

You are implementing a VHT-capable AP. Which one of the following channels is available in the 802.11ac amendment to the 802.11-2012 standard, which was not available in the standard beforethis amendment?
- 153
- 144
- 161
- 56
- 48
Correct Answer

A. 144

Explanation

In the 802.11ac amendment to the 802.11-2012 standard, the channel 144 became available, which was not available in the standard before this amendment.

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22.

You are selecting antennas for a WLAN operating in the 5 GHz frequency band. Whatspecifications should be evaluated for an antenna before it is implemented in this WLAN system?(Choose 3)
- 802.11ad compatibility
- TPC support
- Impedance in Ohms
- Elevation Beamwidth
- Return Loss Rating
- Operating Frequencies
Correct Answer(s)

A. Impedance in Ohms
A. Elevation Beamwidth
A. Operating Frequencies

Explanation

The three specifications that should be evaluated for an antenna before it is implemented in this WLAN system are:

1. Impedance in Ohms: This specification is important as it determines the compatibility and efficiency of the antenna with the WLAN system. A correct impedance match ensures optimal power transfer and signal quality.

2. Elevation Beamwidth: This specification determines the coverage area of the antenna in the vertical direction. It is important to evaluate the elevation beamwidth to ensure that the antenna provides adequate coverage in the desired direction.

3. Operating Frequencies: It is crucial to evaluate the operating frequencies of the antenna to ensure that it is compatible with the WLAN system's 5 GHz frequency band. Using an antenna that operates within the desired frequency range ensures optimal performance and avoids interference issues.

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23.

What is the intended use for the WLAN hardware known as a pole or mast mount unit?
- Mounting a lightning arrestor to a grounding rod
- Mounting an omnidirectional antenna to a mast
- Mounting an RF amplifier to a dipole antenna
- Mounting a PoE injector to a perforated radome
- Mounting an access point to a site survey tripod
Correct Answer

A. Mounting an omnidirectional antenna to a mast

Explanation

The WLAN hardware known as a pole or mast mount unit is intended to be used for mounting an omnidirectional antenna to a mast. This type of hardware allows for secure installation of the antenna on top of a mast or pole, providing optimal coverage and signal distribution in all directions.

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24.

XYZ Corporation is experiencing connectivity problems with their existing building-to-building bridge link. A concrete wall on the roof of one building is partially blocking the Fresnel Zone, and the connection is dropping many frames. The administrator moves the antenna to an area not obstructed by the concrete wall and then realizes the RF cable cannot reach the new location If an extension cable is added to move the antenna, what are the likely results?
- The data throughput rate will increase because VSWR will decrease.
- The Equivalent Isotropically Radiated Power (EIRP) will decrease.
- The antenna’s azimuth beamwidth will decrease.
- The size of the Fresnel zone will increase.
- The likelihood of a direct lightning strike will increase.
Correct Answer

A. The Equivalent Isotropically Radiated Power (EIRP) will decrease.

Explanation

When the antenna is moved to a new location using an extension cable, the Equivalent Isotropically Radiated Power (EIRP) will decrease. EIRP is a measure of the power radiated by an antenna in a specific direction. By adding an extension cable, there will be additional cable losses, resulting in a decrease in the power radiated by the antenna. This decrease in EIRP can lead to a weaker signal and potentially lower data throughput rate.

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25.

When using an RF splitter to connect one transceiver to sector antennas loss is incurred. What isthis loss called?
- Conversion loss
- Through loss
- Active loss
- Intentional loss
Correct Answer

A. Through loss

Explanation

Through loss refers to the loss of signal strength that occurs when using an RF splitter to connect one transceiver to sector antennas. This loss is a result of the signal being divided among multiple antennas, leading to a decrease in overall signal strength.

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26.

What statements accurately describe the RF cables and connectors that are used in an 802.11WLAN system? (Choose 3)
- RF cables have upper and lower frequency range specifications.
- 75 and 125 ohms are the typical impedances of 802.11 WLAN connectors.
- Two RF connectors of the same type (e.g. SMA), manufactured by different companies, may vary in specifications.
- Every RF connector causes insertion loss.
- Large diameter RF cables cause greater loss than small diameter cables.
Correct Answer(s)

A. RF cables have upper and lower frequency range specifications.
A. Two RF connectors of the same type (e.g. SMA), manufactured by different companies, may vary in specifications.
A. Every RF connector causes insertion loss.

Explanation

RF cables have upper and lower frequency range specifications, meaning that they can only effectively transmit signals within a certain frequency range. Two RF connectors of the same type, such as SMA, may vary in specifications when manufactured by different companies. This means that even though they are the same type of connector, they may not have the exact same performance or compatibility. Additionally, every RF connector causes insertion loss, which refers to the decrease in signal strength that occurs when a connector is inserted into a transmission line.

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27.

What statement is true concerning the use of Orthogonal Frequency Division Multiplexing (OFDM)in IEEE 802.11 WLANs?
- 802.11a and 11n use six (6) “pilot” subcarriers as a reference for the receiver to detect frequency and phase shifts of the signal.
- 802.11a/g/n OFDM includes several combinations of modulation and coding to achieve data rates from 1-600 Mbps.
- With 802.11a OFDM, 16-QAM provides either 48 or 54 Mbps data rates, depending upon coding rates.
- 802.11ac VHT-OFDM utilizes 256-QAM, which increases the data rate significantly over 64- QAM available in HT-OFDM.
- In 802.11a OFDM, fifty-six (56) subcarriers are used as parallel symbol transmission paths to carry data.
Correct Answer

A. 802.11ac VHT-OFDM utilizes 256-QAM, which increases the data rate significantly over 64- QAM available in HT-OFDM.

Explanation

802.11ac VHT-OFDM utilizes 256-QAM, which increases the data rate significantly over 64-QAM available in HT-OFDM. This means that 802.11ac VHT-OFDM can transmit more data per symbol, resulting in higher data rates compared to HT-OFDM. By using a higher order modulation scheme, more bits can be encoded into each symbol, allowing for faster transmission speeds. This improvement in data rate is a key advantage of 802.11ac VHT-OFDM over previous OFDM technologies.

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28.

As a consultant, you’ve been hired by XYZ Company to provide recommendations about clientdevice selection, operation, and interoperability. What information should be considered to helpthem choose the right WLAN client devices?
- 802.11n OFDM is more susceptible to high-power, narrowband interference than 802.11a
- In order to earn Wi-Fi Alliance certification, 802.11n clients stations are required to support both 2.4 and 5 GHz frequencies
- 802.11ac devices support the features of the VHT PHY only in the 5 GHz frequency band.
- 802.11ac is not backwardly compatible with 802.11n or 802.11a.
- When HR/DSSS devices are present, VHT MCS rates are disabled for the entire BSS.
Correct Answer

A. 802.11ac devices support the features of the VHT PHY only in the 5 GHz frequency band.

Explanation

The correct answer suggests that when choosing WLAN client devices, it is important to consider that 802.11ac devices only support the features of the VHT PHY in the 5 GHz frequency band. This means that if the company wants to take advantage of the advanced features offered by 802.11ac, they will need to ensure that their network operates on the 5 GHz frequency band.

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29.

Which IEEE 802.11 physical layer (pHY) specifications include support for and compatibility ofboth OFDM and HR/DSSS? (Choose 2)
- HR/DSSS (802.11b)
- OFDM (802.11a)
- ERP (802.11g)
- HT (802.11n)
- CCK (802.11b)
- VHT (802.11ac)
Correct Answer(s)

A. ERP (802.11g)
A. HT (802.11n)

Explanation

The IEEE 802.11g (ERP) specification includes support for both OFDM and HR/DSSS. This means that devices using the 802.11g standard can use either OFDM or HR/DSSS for their physical layer. Similarly, the IEEE 802.11n (HT) specification also includes support for both OFDM and HR/DSSS. Devices using the 802.11n standard can utilize either OFDM or HR/DSSS for their physical layer.

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30.

The IEEE 802.11-2012 standard requires VHT capable devices to be backward compatible withdevices using which other 802.11 physical layer specifications (pHYs)? (Choose 2)
- HT
- OFDM
- HR/DSSS
- ERP-PBCC
- DSSS-OFDM
Correct Answer(s)

A. HT
A. OFDM

Explanation

The IEEE 802.11-2012 standard requires VHT capable devices to be backward compatible with devices using the HT and OFDM physical layer specifications. This means that VHT capable devices must be able to communicate with devices that use the HT and OFDM PHYs. This backward compatibility ensures interoperability between different devices and allows for seamless communication between devices using different physical layer specifications.

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31.

In addition to throughput enhancements, what other improvements does a dual-band 802.11ac APprovide when compared with 802.11a/g APs? (Choose 2)
- Introduces “fast transition” roaming protocols for VoWiFi phones
- Better link reliability between 802.11a/b/g client devices and 802.11ac APs
- Improves service quality for real-time applications at greater distances
- Increases in receive sensitivity enhance RTLS location accuracy
- Stronger security with more robust encryption modes.
- Stronger security with more robust encryption modes.
Correct Answer(s)

A. Better link reliability between 802.11a/b/g client devices and 802.11ac APs
A. Improves service quality for real-time applications at greater distances

Explanation

A dual-band 802.11ac AP provides better link reliability between 802.11a/b/g client devices and 802.11ac APs. This means that the connection between the client devices and the APs is more stable and less prone to interruptions or drops. Additionally, it improves service quality for real-time applications at greater distances. This means that real-time applications, such as video streaming or online gaming, can perform better and have a higher quality of service even when the devices are farther away from the APs.

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32.

What factors are likely to cause the greatest impact on the application layer throughput of an802.11n client station in a 2.4 GHz HT BSS? (Choose 3)
- Use of WEP or TKIP for encryption instead of CCMP
- Use of passphrase authentication instead of 802.1X/EAP authentication
- Increasing the beacon interval from 100 to 200 (TUs)
- RF interference from more than 10 nearby Bluetooth transmitters
- Increasing or decreasing the number of spatial streams in use by the client station and AP
Correct Answer(s)

A. Use of WEP or TKIP for encryption instead of CCMP
A. RF interference from more than 10 nearby Bluetooth transmitters
A. Increasing or decreasing the number of spatial streams in use by the client station and AP

Explanation

The factors that are likely to cause the greatest impact on the application layer throughput of an 802.11n client station in a 2.4 GHz HT BSS are the use of WEP or TKIP for encryption instead of CCMP, RF interference from more than 10 nearby Bluetooth transmitters, and increasing or decreasing the number of spatial streams in use by the client station and AP. WEP and TKIP are less efficient and slower encryption methods compared to CCMP, which can significantly reduce the throughput. RF interference from Bluetooth transmitters can cause signal degradation and decrease the throughput. Additionally, increasing or decreasing the number of spatial streams can affect the overall data rate and throughput of the connection.

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33.

What factors will have the most significant impact on the amount of wireless bandwidth availableto each station within a BSS? (Choose 2)
- The number of client stations associated to the BSS
- The power management settings in the access point’s beacons
- The presence of co-located (10m away) access points on non-overlapping channels
- The data rates at which nearby client stations are transmitting and receiving data
- The layer 3 protocol used by each station to transmit data over the wireless link
Correct Answer(s)

A. The number of client stations associated to the BSS
A. The data rates at which nearby client stations are transmitting and receiving data

Explanation

The number of client stations associated to the BSS will have a significant impact on the amount of wireless bandwidth available to each station because as the number of client stations increases, the available bandwidth needs to be divided among more devices, resulting in reduced bandwidth per station.

The data rates at which nearby client stations are transmitting and receiving data will also have a significant impact on the available wireless bandwidth. If nearby client stations are transmitting and receiving data at high data rates, it can consume a significant portion of the available bandwidth, leaving less bandwidth for other stations in the BSS.

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34.

What are two channel modes specified by the 802.11n (High Throughput) pHY? (Choose 2)
- 20 MHz
- 20/40 MHz
- 40/80 MHz
- 22 MHz
- 80 MHz
- 160 MHz
Correct Answer(s)

A. 20 MHz
A. 20/40 MHz

Explanation

The 802.11n (High Throughput) PHY specifies two channel modes: 20 MHz and 20/40 MHz. These channel modes determine the available bandwidth for wireless communication. The 20 MHz channel mode provides a single 20 MHz wide channel for data transmission. The 20/40 MHz channel mode allows for the aggregation of two 20 MHz channels to provide a wider bandwidth of 40 MHz, which can increase the data throughput.

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35.

In an 802.11 2.4 GHz system, what 22 MHz channels are considered non-overlapping? (Choose2)
- Channels 5 and 10
- Channels 1 and 5
- Channels 3 and 7
- Channels 2 and 8
- Channels 8 and 11
- Channels 10 and 13
Correct Answer(s)

A. Channels 5 and 10
A. Channels 2 and 8
36.

What facts are true regarding controllers and APs in a Split MAC architecture? (Choose 2)
- An IP tunnel is established between the AP and controller for AP management and control functions.
- Using centralized data forwarding, APs never tag Ethernet frames with VLAN identifiers or 802.1p CoS.
- With 802.1X/EAP security, the AP acts as the supplicant and the controller acts as the authenticator.
- Management and data frame types must be processed locally by the AP, while control frame types must be sent to the controller.
- In a distributed data forwarding model, the AP handles frame encryption and decryption.
Correct Answer(s)

A. An IP tunnel is established between the AP and controller for AP management and control functions.
A. In a distributed data forwarding model, the AP handles frame encryption and decryption.

Explanation

In a Split MAC architecture, an IP tunnel is established between the AP and controller for AP management and control functions. This allows the controller to manage and control the AP remotely. Additionally, in a distributed data forwarding model, the AP is responsible for handling frame encryption and decryption. This means that the AP is responsible for securing the data frames that are transmitted between the wireless clients and the network.

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37.

The center frequency of channel 1 in the 2.4 GHz band is 2.412 GHz (2412 MHz).What is the center frequency of channel 4?
- 2.413 GHz
- 2.417 GHz
- 2.422 GHz
- 2.427 GHz
- 2.437 GHz
Correct Answer

A. 2.427 GHz

Explanation

The center frequency of channel 4 can be determined by adding 5 to the center frequency of channel 1. Since the center frequency of channel 1 is 2.412 GHz, adding 5 to it gives us 2.417 GHz. Therefore, the center frequency of channel 4 is 2.417 GHz.

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38.

What answers correctly complete the following sentence?____________ and ____________ carrier sense functions are used to determine if the wirelessmedium is busy. (Choose 2)
- Backoff
- Pseudo-random
- Virtual
- Active
- Physical
- Interframe
- Vector
Correct Answer(s)

A. Virtual
A. Physical

Explanation

Virtual and Physical carrier sense functions are used to determine if the wireless medium is busy. Virtual carrier sense involves monitoring the wireless channel for any ongoing transmissions from other devices, while physical carrier sense involves detecting the presence of any energy or signals on the wireless medium. Both functions are necessary to ensure that a device can accurately determine if the medium is busy before transmitting data.

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39.

In an 802.11n 2.4 GHz BSS, what prevents each station from using the full network bandwidth(e.g. 130 Mbps) for user data throughput when multiple clients are actively exchanging data withthe AP? (Choose 2)
- Radio receiver hardware cannot process data as quickly as it can be transmitted.
- Half of the bandwidth is allocated to uplink traffic and half to downlink traffic.
- The DCF and EDCA coordination functions require backoff algorithms
- WLAN devices cannot detect collisions and must receive positive frame acknowledgment.
- APs do not have sufficient wired connection speeds to the LAN.
Correct Answer(s)

A. The DCF and EDCA coordination functions require backoff algorithms
A. WLAN devices cannot detect collisions and must receive positive frame acknowledgment.

Explanation

The DCF and EDCA coordination functions require backoff algorithms, which introduce a random delay before retransmitting data to avoid collisions. This delay reduces the overall network bandwidth available for user data throughput. Additionally, WLAN devices cannot detect collisions and must receive positive frame acknowledgment, which further affects the network bandwidth as it requires additional time for acknowledgment and retransmission. Therefore, these two factors prevent each station from using the full network bandwidth when multiple clients are actively exchanging data with the AP.

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40.

When a client station sends a broadcast probe request frame with a wildcard SSID, how do APsrespond?
- After waiting a SIFS, all APs reply at the same time with a probe response.
- After waiting a SIFS, a designated AP sends an ACK, and then replies with a probe response.
- Each AP checks with the DHCP server to see if it can respond and then acts accordingly.
- For each probe request frame, only one AP may reply with a probe response.
- Each AP responds in turn after preparing a probe response and winning contention.
Correct Answer

A. Each AP responds in turn after preparing a probe response and winning contention.

Explanation

When a client station sends a broadcast probe request frame with a wildcard SSID, all APs compete for the opportunity to respond. After waiting a SIFS (Short Interframe Space), each AP prepares a probe response and participates in contention to determine which AP will respond first. The AP that wins contention sends its probe response, and then other APs respond in a sequential manner, taking turns after preparing their own probe responses. This ensures that multiple APs do not reply simultaneously, preventing potential collisions and ensuring a more efficient communication process.

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41.

The IEEE 802.11a/n/ac physical layer technologies utilize the 5 GHz frequency band. What is trueof the channels in this frequency spectrum?
- 14 channels are available worldwide
- 11 channels are available worldwide.
- Regulatory domains worldwide require DFS and TPC in all these channels.
- DFS may be required in some regulatory domains on some channels.
- 802.11 channels are separated by 5 Mhz
Correct Answer

A. DFS may be required in some regulatory domains on some channels.

Explanation

DFS (Dynamic Frequency Selection) may be required in some regulatory domains on some channels. The 5 GHz frequency band used by IEEE 802.11a/n/ac has a limited number of available channels. In order to avoid interference with radar systems, certain channels require DFS, which is a mechanism that allows devices to detect and avoid radar signals. However, not all regulatory domains require DFS on all channels, so it may only be required in certain regions on specific channels.

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42.

What features were introduced in the IEEE 802.11h amendment in order to uphold regulatoryrequirements for 5 GHz operation? (Choose 2)
- 256-QAM
- Distributed Coordination Function (DCF)
- Phase Shift Keying (PSK)
- Transmit Power Control (TPC)
- Radio Resource Management (RRM)
- Dynamic Frequency Selection (DFS)
Correct Answer(s)

A. Transmit Power Control (TPC)
A. Dynamic Frequency Selection (DFS)

Explanation

The IEEE 802.11h amendment introduced Transmit Power Control (TPC) and Dynamic Frequency Selection (DFS) features in order to uphold regulatory requirements for 5 GHz operation. TPC allows devices to adjust their transmit power levels to ensure they operate within the allowed limits set by regulatory bodies. DFS enables devices to dynamically select and avoid using channels that are being used by radar systems, thus preventing interference with these systems and ensuring compliance with regulatory requirements. These features help ensure that wireless networks operating in the 5 GHz frequency range adhere to regulatory guidelines and minimize interference with other systems.

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43.

The OSI model is a 7-layer model for understanding the functions of a communication system.What OSI sublayers are specifically addressed by the IEEE 802.11-2012 standard? (Choose 2)
- Network
- PPDU
- PLCP
- MAC
- IP
- Transport
Correct Answer(s)

A. PLCP
A. MAC

Explanation

The IEEE 802.11-2012 standard specifically addresses the Physical Layer Convergence Procedure (PLCP) and Media Access Control (MAC) sublayers of the OSI model. These two sublayers are crucial in the functioning of a communication system as they handle the physical transmission of data and the access control to the medium, respectively. The PLCP sublayer is responsible for converting data into a format suitable for transmission, while the MAC sublayer manages the access to the shared communication medium.

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44.

Which of the following frequency ranges are specified for use by IEEE 802.11 radios? (Choose all that apply.)
- 902 - 928 MHz
- 2.4000 – 2.4835 GHz
- 5.15 – 5.25 GHz
- 5.470 – 5.725 GHz
- 5.725 – 5.875 GHz
Correct Answer(s)

A. 2.4000 – 2.4835 GHz
A. 5.15 – 5.25 GHz
A. 5.470 – 5.725 GHz
A. 5.725 – 5.875 GHz

Explanation

The specified frequency ranges for use by IEEE 802.11 radios are 2.4000 – 2.4835 GHz, 5.15 – 5.25 GHz, 5.470 – 5.725 GHz, and 5.725 – 5.875 GHz. These frequency ranges are within the commonly used 2.4 GHz and 5 GHz bands for Wi-Fi communication. The IEEE 802.11 standard defines these frequency ranges to ensure compatibility and avoid interference between different Wi-Fi devices operating in the same area.

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45.

Which data rate is supported by 802.11g radios that is not supported by 802.11a radios?
- 9 Mbps
- 11 Mbps
- 12 Mbps
- 54 Mbps
- 65 Mbps
- 130 Mbps
Correct Answer

A. 11 Mbps

Explanation

802.11g radios support a data rate of 11 Mbps, which is not supported by 802.11a radios. The 802.11a standard supports data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps, while the 802.11g standard supports data rates of 1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48, and 54 Mbps. Therefore, the correct answer is 11 Mbps.

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46.

A Wi-Fi Alliance interoperability certificate indicates that a device is a/b/g/n certified. It furtherindicates one transmit and receive spatial stream for both the 2.4 GHz and 5.0 GHz bands. Itfurther indicates support for both WPA and WPA2 Enterprise and Personal. Finally, it indicatessupport for EAP-TLS, EAP-TTLS/MSCHAPv2, PEAPv0/EAP-MSCHAPv2 and PEAPv1/EAP-GTC.Which one of the following statements is false?
- This client device supports protection mechanisms such as RTS/CTS and/or CTS-to-Self.
- This client device supports both TKIP and CCMP cipher suites.
- 300 Mbps is the maximum supported data rate for this device.
- This client device supports the ERP, OFDM, and HT physical layer specifications.
- This client device supports X.509 certificates for EAP authentication
Correct Answer

A. 300 Mbps is the maximum supported data rate for this device.

Explanation

The given statement is false because the question states that the device is certified as a/b/g/n, which means it supports up to 600 Mbps data rate for 2.4 GHz band and up to 1300 Mbps data rate for 5.0 GHz band. Therefore, the maximum supported data rate for this device is not 300 Mbps.

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47.

When a client moves to a new BSS within an ESS, what steps are part of the 802.11 reassociationprocess? (Choose 2)
- The client station transmits a Reassociation Request frame to its current access point.
- The current access point informs the IP gateway of the reassociation.
- The current access point triggers the client’s reassociation service.
- The new access point transmits a Reassociation Response to the client station with a status value.
- The client and new access point create unicast encryption keys.
- The client station transmits a deauthentication frame to the current access point
Correct Answer(s)

A. The new access point transmits a Reassociation Response to the client station with a status value.
A. The client and new access point create unicast encryption keys.

Explanation

When a client moves to a new BSS within an ESS, two steps that are part of the 802.11 reassociation process are: the new access point transmits a Reassociation Response to the client station with a status value, and the client and new access point create unicast encryption keys. These steps ensure that the client successfully associates with the new access point and establishes secure communication with it.

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48.

In an enterprise WLAN, what condition will prevent a dual-band VHT/HT client device fromperforming a fast and seamless transition (i.e. latency-sensitive applications are not disrupted)between two access points that are managed by the same WLAN controller?
- The current AP is using channel 1 and the new AP is using channel 40.
- The SSID of the current AP does not match the SSID of the new AP.
- The current AP supports only HT and the new AP is VHT capable.
- The access points are hiding the SSID in Beacons and Probe Response frames
Correct Answer

A. The SSID of the current AP does not match the SSID of the new AP.

Explanation

If the SSID of the current AP does not match the SSID of the new AP, it will prevent a dual-band VHT/HT client device from performing a fast and seamless transition between the two access points. This is because the client device needs to authenticate and associate with the new AP, and if the SSID does not match, the client device will not be able to connect to the new AP. As a result, latency-sensitive applications may be disrupted during the transition.

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49.

What statements about the SSID are true? (Choose 2)
- The SSID is a security session identifier used in RSNs.
- The SSID must be included in an association request frame.
- The SSID is an alphanumeric value assigned to device manufacturers by the IEEE.
- The SSID is a pseudo-random number assigned to each client by an AP.
- The SSID is an alphanumeric value with a maximum length of 32 octets.
- When configuring a new network, creating an SSID is optional.
Correct Answer(s)

A. The SSID must be included in an association request frame.
A. The SSID is an alphanumeric value with a maximum length of 32 octets.

Explanation

The SSID must be included in an association request frame because it is used to identify the network that the client wants to connect to. The SSID is an alphanumeric value with a maximum length of 32 octets, which means it can consist of both letters and numbers and cannot exceed 32 characters in length. This is the standard limit set by the IEEE for SSID values.

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Certified Wireless Network Professional (CWNA) Quiz

What can cause an excessively high VSWR (Voltage Standing Wave Ratio) in a WLAN RFtransmission line?

Quiz Preview

What word describes the bending of an RF signal as it passes through a medium of a varyingdensity from that of free space?

What factors influence the distance that an RF signal can be effectively received? (Choose 3)

As an RF wave propagates through space, the wave front experiences natural expansion thatreduces its signal strength in an area. What term describes the rate at which this expansionhappens?

Return Loss is the decrease of forward energy in a system when some of the power is beingreflected back toward the transmitter.What will cause high return loss in an RF transmission system, including the radio, cables,connectors and antenna?

What factors are taken into account when calculating the Link Budget of a point-to-point outdoorWLAN bridge link?

A WLAN transmitter that emits a 200 mW signal is connected to a cable with 3 dB loss.If the cable is connected to an antenna with 10 dBi gain, what is the EIRP at the antenna element?

In a long-distance RF link, what statement about Fade Margin is true?

Which unit of measurement is an absolute unit that is used to quantify power levels on a linearscale?

An 802.11 WLAN transmitter that emits a 50 mW signal is connected to a cable with 3 dB of loss.The cable is connected to an antenna with 16 dBi of gain.What is the EIRP power output?

What is always required to establish a high quality 2.4 GHz RF link at a distance of 3 miles(5 kilometers)?

What phrase defines Equivalent Isotropically Radiated Power (EIRP)?

What term describes the effect of increasing the intensity of an RF wave with an antenna byfocusing the energy in a specific direction?

Which antenna types are commonly used by indoor Wi-Fi devices in a MIMO diversityimplementation? (Choose 2)

What phrase correctly completes the following sentence?When using WMM Power Save operation, a wireless client device ______________.

When replacing the antenna of a WLAN device with a similar antenna type that has a higherpassive gain, what antenna characteristic will decrease?

What statements about the beamwidth of an RF antenna are true? (Choose 2)

What HT technology requires MIMO support on both the transmitter and receiver?

ABC Company has just purchased a 6 dBi patch antenna. After performing some tests with the 6 dBi antenna, they have concluded that more antenna gain is needed to cover their outdoor courtyard. When choosing an antenna with higher gain, what other antenna characteristic will also always change?

AP-1 is a 3x3:2 AP. STA-3 is a 3x3:3 client. What is the maximum number of spatial streams thatcan be used for a downlink HT-OFDM transmission from AP-1 to STA-3?

You are implementing a VHT-capable AP. Which one of the following channels is available in the 802.11ac amendment to the 802.11-2012 standard, which was not available in the standard beforethis amendment?

You are selecting antennas for a WLAN operating in the 5 GHz frequency band. Whatspecifications should be evaluated for an antenna before it is implemented in this WLAN system?(Choose 3)

What is the intended use for the WLAN hardware known as a pole or mast mount unit?

When using an RF splitter to connect one transceiver to sector antennas loss is incurred. What isthis loss called?

What statements accurately describe the RF cables and connectors that are used in an 802.11WLAN system? (Choose 3)

What statement is true concerning the use of Orthogonal Frequency Division Multiplexing (OFDM)in IEEE 802.11 WLANs?

As a consultant, you’ve been hired by XYZ Company to provide recommendations about clientdevice selection, operation, and interoperability. What information should be considered to helpthem choose the right WLAN client devices?

Which IEEE 802.11 physical layer (pHY) specifications include support for and compatibility ofboth OFDM and HR/DSSS? (Choose 2)

The IEEE 802.11-2012 standard requires VHT capable devices to be backward compatible withdevices using which other 802.11 physical layer specifications (pHYs)? (Choose 2)

In addition to throughput enhancements, what other improvements does a dual-band 802.11ac APprovide when compared with 802.11a/g APs? (Choose 2)

What factors are likely to cause the greatest impact on the application layer throughput of an802.11n client station in a 2.4 GHz HT BSS? (Choose 3)

What factors will have the most significant impact on the amount of wireless bandwidth availableto each station within a BSS? (Choose 2)

What are two channel modes specified by the 802.11n (High Throughput) pHY? (Choose 2)

In an 802.11 2.4 GHz system, what 22 MHz channels are considered non-overlapping? (Choose2)

What facts are true regarding controllers and APs in a Split MAC architecture? (Choose 2)

The center frequency of channel 1 in the 2.4 GHz band is 2.412 GHz (2412 MHz).What is the center frequency of channel 4?

What answers correctly complete the following sentence?____________ and ____________ carrier sense functions are used to determine if the wirelessmedium is busy. (Choose 2)

In an 802.11n 2.4 GHz BSS, what prevents each station from using the full network bandwidth(e.g. 130 Mbps) for user data throughput when multiple clients are actively exchanging data withthe AP? (Choose 2)

When a client station sends a broadcast probe request frame with a wildcard SSID, how do APsrespond?

The IEEE 802.11a/n/ac physical layer technologies utilize the 5 GHz frequency band. What is trueof the channels in this frequency spectrum?

What features were introduced in the IEEE 802.11h amendment in order to uphold regulatoryrequirements for 5 GHz operation? (Choose 2)

The OSI model is a 7-layer model for understanding the functions of a communication system.What OSI sublayers are specifically addressed by the IEEE 802.11-2012 standard? (Choose 2)

Which of the following frequency ranges are specified for use by IEEE 802.11 radios? (Choose all that apply.)

Which data rate is supported by 802.11g radios that is not supported by 802.11a radios?

When a client moves to a new BSS within an ESS, what steps are part of the 802.11 reassociationprocess? (Choose 2)

In an enterprise WLAN, what condition will prevent a dual-band VHT/HT client device fromperforming a fast and seamless transition (i.e. latency-sensitive applications are not disrupted)between two access points that are managed by the same WLAN controller?

What statements about the SSID are true? (Choose 2)

What answers correctly complete the following sentence? and carrier sense functions are used to determine if the wirelessmedium is busy. (Choose 2)