Deck 8: High-Speed Wlans and Wlan Security

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

Answer 1

C

Question 2

Wireless controllers incorporate most AP functions including the radio.

Answer 2

False

Question 3

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

Answer 3

False

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

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

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

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

Question 8

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

A) 23
B) 11
C) 3
D) 8

Question 9

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

A) 16
B) 2
C) 4
D) 8

Question 10

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

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

Question 13

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

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

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

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

Question 17

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

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

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

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

Question 21

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
a transmission technique that uses multiple radios and multiple antennas to send different parts of the same message simultaneously

Question 22

AP _____________________ is a security problem that takes advantage of the fact that clients authenticate with the AP but not vice versa.

Question 23

The strength of encryption relies on keeping the __________ secret as well as its length.

Question 24

What 802.11n mode of operation is referred to as greenfield?

A) transmitting in non-HT mode with 802.11a/g devices
B) transmitting in mixed HT/non-HT devices
C) transmitting with only HT devices
D) transmitting at a faster speed than receiving

Question 25

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
caused when the beginning of a symbol arrives at the receiver antenna while multipath reflections from the previous symbol are still reaching the antenna

Question 26

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
interference between two devices configured to use the same frequency channel

Question 27

__________________ distortion occurs when the receiving device gets the same signal from several different directions at different times.

Question 28

What type of device can you deploy to allow client WLAN connectivity when the main AP is out of range?

A) bridge
B) controller
C) monitor
D) router

Question 29

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
the unused frequency space between two adjacent channels

Question 30

The _______________ interval prevents a new symbol from arriving at the receiver before the last multipath signal reaches the receiver's antenna.

Question 31

Which IEEE standard supports QoS and enables prioritization of frames in DCF?

A) 802.11f
B) 802.11e
C) 802.11d
D) 802.11c

Question 32

What is the U-NII frequency band and WLAN standard uses it?

Question 33

Which HT operation mode is used when one or more non-HT devices are associated with an HT AP and supports devices at 20 or 40 MHz?

A) Mode 0
B) Mode 1
C) Mode 2
D) Mode 3

Question 34

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
a change in the signal, also known as a baud

Question 35

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
a security protocol used in WPA that provides per packet key-mixing

Question 36

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
a coordination method used by 802.11g devices that prevents 802.11 and 802.11b devices that do not "understand" OFDM from attempting to initiate a transmission

Question 37

What 802.11 standard under development uses up to 160 MHz bandwidth and can achieve data rates up to 7 Gbps?

A) 802.11bg
B) 802.11ac
C) 802.11cd
D) 802.11ga

Question 38

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
devices that make it much easier to manage large WLANs by implementing most of the functions of an AP

Question 39

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
a 2-microsecond interframe space that can be used in 802.11n networks

Question 40

MATCHING
a. co-channel interference
b. CTS-to-self
c. guard band
d. intersymbol interference
e. pre-shared key
f. reduced interframe space
g. spatial multiplexing
h. symbol
i. TKIP
j. wireless controller
a 128-bit key used by WPA

Question 41

What are the three parts of an 802.11a PLCP frame? Describe them briefly.

Question 42

What are the two mandatory and two optional transmission modes defined in the 802.11g PHY layer?

Question 43

Describe how 802.11a uses the U-NII-1, U-NII-2, and U-NII-2 extended bands.

Question 44

What are wireless controllers and why are they important in WLANs?

Question 45

What is the guard interval and what does it help prevent?

Question 46

Describe the approach that 802.11n (HT) takes to the implementation of the PHY layer.

Question 47

What is 802.11i and what aspect of WLANs does it deal with?

Question 48

What is the channel configuration of 802.11n and how does it help achieve higher data rates?

Question 49

What is MIMO technology? Include beamforming and spatial multiplexing in your answer.