Question 1

Which field in an 802.11a PLCP frame are used to initialize part of the transmitter and receiver circuits?
A) Tail
B) Pad
C) Service
D) Parity

Accepted Answer

The Service field in an 802.11a PLCP frame is used for initializing part of the transmitter and receiver circuits. The Tail field is used for ensuring the correct synchronization and completion of the frame, the Pad field is used for padding the frame to a specific length, and the Parity field is used for error detection and correction.

Question 2

Wireless controllers incorporate most AP functions including the radio.

Accepted Answer

Wireless controllers manage multiple access points (APs) but do not incorporate the radio functions themselves; those are part of the individual APs.

Question 3

VPNs encrypt a connection for security and use very few processing resources.

Accepted Answer

VPNs do encrypt connections for security, but the encryption and decryption processes can consume a significant amount of processing resources, especially on devices with limited computing power.

Question 4

What is the maximum radio configuration for 802.11n devices?
A) 3 transmitters, 3 receivers
B) 6 transmitters, 4 receivers
C) 4 transmitters, 4 receivers
D) 4 transmitters, 3 receivers

Accepted Answer

The maximum radio configuration for 802.11n devices is 4 transmitters and 4 receivers, often referred to as a 4x4 configuration. This setup allows for increased data rates and improved signal reliability compared to configurations with fewer transmitters and receivers.

Question 5

What is the multiplexing technique used by 802.11a to help solve the multipath distortion problem?
A) QPSK
B) OFDM
C) FEC
D) PBCC

Accepted Answer

802.11a uses Orthogonal Frequency Division Multiplexing (OFDM) to help solve the multipath distortion problem. OFDM divides the data into multiple subcarriers that are transmitted simultaneously, each with slightly different frequencies. This enables the receiver to accurately reconstruct the original signal, even if some of the subcarriers are attenuated or delayed due to multipath distortion.

Question 6

What do 802.11n devices employ to direct a transmission back to the device from which a frame was received?
A) spatial multiplexing
B) beamforming
C) MIMO
D) antenna diversity

Accepted Answer

802.11n devices employ beamforming to direct a transmission back to the device from which a frame was received. Beamforming uses multiple antennas to transmit signals directly toward the receiving device, allowing for better signal strength and reliability. Spatial multiplexing, MIMO, and antenna diversity are also used in 802.11n devices, but they do not specifically address the issue of directing transmissions back to the originating device.

Question 7

Which wireless data rate uses 64-level quadrature amplitude modulation, transmitting over 48 subcarriers?
A) 11 Mbps
B) 2 Mbps
C) 24 Mbps
D) 54 Mbps

Accepted Answer

The wireless data rate that uses 64-level quadrature amplitude modulation and transmits over 48 subcarriers is 54 Mbps. This is a part of the IEEE 802.11a standard, which uses a frequency band of 5 GHz and can achieve higher data rates compared to the 2.4 GHz frequency band used by the IEEE 802.11b/g standards. Therefore, the correct choice is D.

Question 8

How many non-overlapping channels are available in an 802.11g WLAN?
A) 23
B) 11
C) 3
D) 8

Accepted Answer

In an 802.11g WLAN, there are 3 non-overlapping channels available (1, 6, and 11) in the 2.4 GHz band, which is commonly used to avoid interference between channels.

Question 9

How many bits per symbol can be transmitted using 16-QAM?
A) 16
B) 2
C) 4
D) 8

Accepted Answer

16-QAM transmits 4 bits per symbol, as it uses a 16-point constellation, where 2^4 = 16.

Question 10

The 4-bit Rate field in an 802.11a PLCP frame specifies the speed at which the Data field will be transmitted.

Accepted Answer

The 4-bit Rate field in an 802.11a PLCP frame specifies the speed at which the Data field will be transmitted.

Question 11

Which layer defines the characteristics of the wireless medium?
A) PLCP
B) PMD
C) LLC
D) MAC

Accepted Answer

The answer of Which layer defines the characteristics of the...

Question 12

How much bandwidth do 802.11n devices utilize when running at speeds up to 300 Mbps?
A) 20 MHz
B) 22 MHz
C) 40 MHz
D) 44 MHz

Accepted Answer

802.11n devices use 40 MHz bandwidth when running at speeds up to 300 Mbps.

Question 13

The 802.11a standard maintains the same MAC layer functions as 802.11b WLANs.

Accepted Answer

Both 802.11a and 802.11b standards use the same MAC (Media Access Control) layer, as they are both part of the IEEE 802.11 family of standards, which defines the operation of WLANs. The primary differences between them lie in their physical layer (PHY) specifications, such as frequency band and data rate, not in their MAC layer functions.

Question 14

Which of the U-NII bands is approved for outdoor use?
A) U-NII-1
B) U-NII-2
C) U-NII-2 Extended
D) U-NII-3

Accepted Answer

The answer of Which of the U-NII bands is approved...

Question 15

Which of the following 802.11 standards uses U-NII bands and does not use ISM bands?
A) 802.11b
B) 802.11a
C) 802.11g
D) 802.11n

Accepted Answer

802.11a uses U-NII bands (5 GHz) and does not use ISM bands (2.4 GHz).

Question 16

Why is the SIFS time in the 802.11g standard effectively extended to 16 microseconds?
A) for compatibility with 802.11a
B) to account for quiet time
C) to allow 802.11n devices on the network
D) to achieve data rates higher than 11 Mbps

Accepted Answer

The SIFS time in the 802.11g standard is effectively extended to 16 microseconds to account for quiet time. This allows for more accurate timing of transmissions and receptions, reducing the chances of collisions and improving the reliability of the network. It has nothing to do with compatibility with other standards, accommodating newer devices or achieving higher data rates.

Question 17

Increasing data transmission speed through more complex modulation schemes makes multipath distortion worse.

Accepted Answer

As data transmission speed increases, more complex modulation schemes are used to encode the data onto the carrier waveform. However, these complex modulation schemes are more susceptible to multipath distortion, which occurs when the transmitted signal takes multiple paths to reach the receiver and the multiple versions of the signal interfere with each other. This can cause errors in the received data and reduce the overall data transmission speed.

Question 18

What is the disadvantage of an 802.11a WLAN compared to an 802.11b WLAN?
A) shorter range
B) higher error rate
C) more interference sources
D) lower bandwidth

Accepted Answer

802.11a WLAN operates at a higher frequency (5 GHz) than 802.11b (2.4 GHz), which generally results in a shorter range due to the higher frequency's lower ability to penetrate obstacles.

Question 19

What is the purpose of a guard band?
A) help prevent adjacent channel interference
B) help prevent co-channel interference
C) helps prevent outside EM interference
D) helps prevent intersymbol interference

Accepted Answer

A guard band is a frequency band that is allocated between two adjacent frequency bands to help prevent adjacent channel interference. It acts as a buffer zone to reduce interference between signals transmitted in adjacent channels.

Question 20

Which of the following is correct about antenna diversity?
A) it is the cornerstone of the 802.11n technology
B) it is two radios and one antenna
C) it increases bandwidth while decreasing range
D) it is two antennas with one radio

Accepted Answer

Antenna diversity is usually implemented as two antennas with one radio, which helps to improve signal strength and reduce the effects of multipath interference. It is commonly used in Wi-Fi and cellular technologies to improve wireless communication reliability and range. Option A is incorrect because while antenna diversity is a feature in 802.11n, it is not the sole cornerstone of the technology. Option B is incorrect because it is describing MIMO technology, which has multiple radios and antennas. Option C is incorrect because antenna diversity is used to improve range, not decrease it.

Quiz 8: High-Speed Wlans and Wlan Security

Which field in an 802.11a PLCP frame are used to initialize part of the transmitter and receiver circuits?

Wireless controllers incorporate most AP functions including the radio.

VPNs encrypt a connection for security and use very few processing resources.

What is the maximum radio configuration for 802.11n devices?

What is the multiplexing technique used by 802.11a to help solve the multipath distortion problem?

What do 802.11n devices employ to direct a transmission back to the device from which a frame was received?

Which wireless data rate uses 64-level quadrature amplitude modulation, transmitting over 48 subcarriers?

How many non-overlapping channels are available in an 802.11g WLAN?

How many bits per symbol can be transmitted using 16-QAM?

The 4-bit Rate field in an 802.11a PLCP frame specifies the speed at which the Data field will be transmitted.

Which layer defines the characteristics of the wireless medium?

How much bandwidth do 802.11n devices utilize when running at speeds up to 300 Mbps?

The 802.11a standard maintains the same MAC layer functions as 802.11b WLANs.

Which of the U-NII bands is approved for outdoor use?

Which of the following 802.11 standards uses U-NII bands and does not use ISM bands?

Why is the SIFS time in the 802.11g standard effectively extended to 16 microseconds?

Increasing data transmission speed through more complex modulation schemes makes multipath distortion worse.

What is the disadvantage of an 802.11a WLAN compared to an 802.11b WLAN?

What is the purpose of a guard band?

Which of the following is correct about antenna diversity?