CWNA Assessment Test
At which layers of the OSI model does 802.11 technology operate? - answer• Data-link
& Physical layers
EXPLANATION: The IEEE 802.11-2012 standard defines communication mechanisms
at only the Physical layer and MAC sublayer of the Data-Link layer of the OSI model.
Which Wi-Fi Alliance certification defines the mechanism for conserving battery life that
is critical for handheld devices such as bar code scanners and VoWiFi phones? -
answer• WMM-PS
EXPLANATION: WMM-PS helps conserve battery power for devices using Wi-Fi radios
by managing the time the client device spends in sleep mode. Conserving battery life is
critical for handheld devices such as bar code scanners and VoWiFi phones. To take
advantage of power-saving capabilities, both the device and the access point must
support WMM Power Save.
Which of these frequencies has the longest wavelength? - answer• 750 KHz
EXPLANATION: A 750 KHz signal has an approximate wavelength of 1,312 feet, or 400
meters. A 252 GHz signal has an approximate wavelength of less than 0.05 inches, or
1.2 millimeters. Remember, the higher the frequency of a signal, the smaller the
wavelength property of an electromagnetic signaL.
Which of these terms can best be used to compare the relationship between two radio
waves that share the same frequency? - answer• Phase
EXPLANATION: Phase involves the positioning of the amplitude crests and troughs of
two wave- forms.
A bridge transmits at 10 mW. The cable to the antenna produces a loss of 3 dB, and the
antenna produces a gain of 20 dBi. What is the EIRP? - answer• 500 mW
EXPLANATION: The 10 mW of power is decreased by 3 dB, or divided by 2, giving 5
mW. This is then increased by 20 dBi, or multiplied by 10 twice, giving 500 mW.
dBi is an expression of what type of measurement? - answer• Antenna gain
EXPLANATION: Theoretically, an isotropic radiator can radiate an equal signal in all
directions. An antenna cannot do this because of construction limitations. However,
antennas are often referred to as isotropic radiators because they radiate RF energy.
, The gain, or increase, of power from an antenna when compared to what an isotropic
radiator would generate is known as decibels isotropic (dBi). Another way of phrasing
this is decibel gain referenced to an isotropic radiator, or change in power relative to an
antenna. dBi is a measurement of antenna gain.
What are some possible effects of voltage standing wave ratio (VSWR)? - answer•
Decreased signal strength
• Transmitter failure
• Erratic amplitude.
EXPLANATION: Reflected voltage caused by an impedance mismatch may cause a
degradation of amplitude, erratic signal strength, or even the worst-case scenario of
transmitter burnout.
When installing a higher-gain omnidirectional antenna, which of the following occurs? -
answer• The horizontal coverage increases
• The vertical coverage decreases.
EXPLANATION: When the gain of an omnidirectional antenna is increased, the vertical
cover- age area decreases while the horizontal coverage area is increased.
802.11a OFDM radios are backward compatible with which IEEE 802.11 radios? -
answer• OFDM is not backward compatible because of its 5 GHz band.
EXPLANATION: 802.11a (OFDM) radios transmit in the 5 GHz U-NII bands and are not
compatible with 802.11 legacy (FHSS) radios, 802.11 legacy (DSSS) radios, 802.11b
(HR-DSSS) radios, or 802.11g (ERP) radios, which transmit in the 2.4 GHz ISM
frequency band. 802.11a (OFDM) radios are forward compatible but not backward
compatible with 802.11n (HT) radios. 802.11n radios, which can transmit on either
frequency band, are backward compatible with 802.11a radios as well as 802.11g
(ERP), 802.11b (HR- DSSS), and 802.11 legacy (DSSS) radios. None of these radio
technologies are backward compatible with 802.11 legacy (FHSS) radios.
Which IEEE 802.11 amendment specifies the use of up to eight spatial streams of
modulated data bits? - answer• IEEE 802.11ac
EXPLANATION: The 802.11ac-2013 amendment defines the use of 256-QAM
modulation, up to eight spatial streams, multiuser MIMO, 80 MHz channels, and 160
MHz channels. 802.11 MIMO technology and 40 MHz channels debuted with the
ratification of the 802.11n-2009 amendmenT.
The FCC is preparing for the advent of 802.11ac technology that can use 80 MHz and
160 MHz channels, and therefore, more unlicensed spectrum is needed. What are the
newly proposed 5 GHz frequency bands? - answer• U-NII-2B
• U-NII-4
At which layers of the OSI model does 802.11 technology operate? - answer• Data-link
& Physical layers
EXPLANATION: The IEEE 802.11-2012 standard defines communication mechanisms
at only the Physical layer and MAC sublayer of the Data-Link layer of the OSI model.
Which Wi-Fi Alliance certification defines the mechanism for conserving battery life that
is critical for handheld devices such as bar code scanners and VoWiFi phones? -
answer• WMM-PS
EXPLANATION: WMM-PS helps conserve battery power for devices using Wi-Fi radios
by managing the time the client device spends in sleep mode. Conserving battery life is
critical for handheld devices such as bar code scanners and VoWiFi phones. To take
advantage of power-saving capabilities, both the device and the access point must
support WMM Power Save.
Which of these frequencies has the longest wavelength? - answer• 750 KHz
EXPLANATION: A 750 KHz signal has an approximate wavelength of 1,312 feet, or 400
meters. A 252 GHz signal has an approximate wavelength of less than 0.05 inches, or
1.2 millimeters. Remember, the higher the frequency of a signal, the smaller the
wavelength property of an electromagnetic signaL.
Which of these terms can best be used to compare the relationship between two radio
waves that share the same frequency? - answer• Phase
EXPLANATION: Phase involves the positioning of the amplitude crests and troughs of
two wave- forms.
A bridge transmits at 10 mW. The cable to the antenna produces a loss of 3 dB, and the
antenna produces a gain of 20 dBi. What is the EIRP? - answer• 500 mW
EXPLANATION: The 10 mW of power is decreased by 3 dB, or divided by 2, giving 5
mW. This is then increased by 20 dBi, or multiplied by 10 twice, giving 500 mW.
dBi is an expression of what type of measurement? - answer• Antenna gain
EXPLANATION: Theoretically, an isotropic radiator can radiate an equal signal in all
directions. An antenna cannot do this because of construction limitations. However,
antennas are often referred to as isotropic radiators because they radiate RF energy.
, The gain, or increase, of power from an antenna when compared to what an isotropic
radiator would generate is known as decibels isotropic (dBi). Another way of phrasing
this is decibel gain referenced to an isotropic radiator, or change in power relative to an
antenna. dBi is a measurement of antenna gain.
What are some possible effects of voltage standing wave ratio (VSWR)? - answer•
Decreased signal strength
• Transmitter failure
• Erratic amplitude.
EXPLANATION: Reflected voltage caused by an impedance mismatch may cause a
degradation of amplitude, erratic signal strength, or even the worst-case scenario of
transmitter burnout.
When installing a higher-gain omnidirectional antenna, which of the following occurs? -
answer• The horizontal coverage increases
• The vertical coverage decreases.
EXPLANATION: When the gain of an omnidirectional antenna is increased, the vertical
cover- age area decreases while the horizontal coverage area is increased.
802.11a OFDM radios are backward compatible with which IEEE 802.11 radios? -
answer• OFDM is not backward compatible because of its 5 GHz band.
EXPLANATION: 802.11a (OFDM) radios transmit in the 5 GHz U-NII bands and are not
compatible with 802.11 legacy (FHSS) radios, 802.11 legacy (DSSS) radios, 802.11b
(HR-DSSS) radios, or 802.11g (ERP) radios, which transmit in the 2.4 GHz ISM
frequency band. 802.11a (OFDM) radios are forward compatible but not backward
compatible with 802.11n (HT) radios. 802.11n radios, which can transmit on either
frequency band, are backward compatible with 802.11a radios as well as 802.11g
(ERP), 802.11b (HR- DSSS), and 802.11 legacy (DSSS) radios. None of these radio
technologies are backward compatible with 802.11 legacy (FHSS) radios.
Which IEEE 802.11 amendment specifies the use of up to eight spatial streams of
modulated data bits? - answer• IEEE 802.11ac
EXPLANATION: The 802.11ac-2013 amendment defines the use of 256-QAM
modulation, up to eight spatial streams, multiuser MIMO, 80 MHz channels, and 160
MHz channels. 802.11 MIMO technology and 40 MHz channels debuted with the
ratification of the 802.11n-2009 amendmenT.
The FCC is preparing for the advent of 802.11ac technology that can use 80 MHz and
160 MHz channels, and therefore, more unlicensed spectrum is needed. What are the
newly proposed 5 GHz frequency bands? - answer• U-NII-2B
• U-NII-4
