FACULTY OF

COMPUTER SCIENCE & ENGINEERING

Chapter 05. MAC and Physical Layers

QUESTION 1

1. Which of the following service sets can use

distributed coordination function (DCF)

mode? Choose all that apply.

A. BSS

B. IBSS

C. ESS

D. IESS

QUESTION 2

2. Which of the following service sets can use

point coordination function (PCF) mode?

Choose all that apply.

A. BSS

B. IBSS

C. ESS

D. IESS

QUESTION 3

3. You have a large number of users on one

access point and collisions are becoming a

problem, causing reduced throughput. Some of

the users are developers that do a significant

amount of large file transfers during the day.

Which RTS/CTS setting would best fix this

problem?

A. On

B. Off

C. On with threshold

QUESTION 4

4. Which one of the following is an advantage

to using point coordination function (PCF)

mode over distributed coordination mode

(DCF)?

A. PCF has a lower overhead than using DCF

B. PCF can be used in and IBSS while DCF cannot

C. PCF uses CSMA/CA while DCF does not

D. PCF provides a given level of QoS

QUESTION 5

5. After a client station sends a data packet

to another client station, the receiving

station replies with an acknowledgement

after which interframe space?

A. IFS

B. SIFS

C. PIFS

D. DIFS

QUESTION 6

6. Why is the CSMA/CA protocol used in order

to avoid collisions in a wireless LAN?

A. PCF mode requires use of a polling mechanism

B. The overhead of sending acknowledgements

is high

C. All clients must acknowledge packets received

while they're asleep

D. It is not possible to detect collisions on a

wireless LAN

QUESTION 7

7. End stations will broadcast a _______ when

actively scanning for access points on the

network.

A. Beacon management frame

B. Superframe

C. Probe request frame

D. Request to send

QUESTION 8

8. PIFS are only used during the

communications of a wireless LAN when which

of the following have occurred?

A. The network is in point coordination function

mode

B. The access point has been configured to use

RTS/CTS

C. The access point has been configured to use

CSMA/CD

D. The network is configured for fragmentation

QUESTION 9

9. You have just finished installing your first

wireless LAN with 802.11b equipment rated at 11

Mbps. After testing the throughput of the clients,

you find your actual throughput is only 5.5 Mbps.

What is the likely cause of this throughput?

A. Wireless LANs use RTS/CTS by default

B. Wireless LANs use the CSMA/CA protocol

C. Use of PCF is reducing network throughput

D. DRS has caused all of the clients to decrease their

data rates

QUESTION 10

10. You have just finished installing your first

wireless LAN with 802.11b equipment rated at 11

Mbps. After testing the throughput of the clients

you find your actual throughput is only 5.5 Mbps.

What can you change to get 11Mbps throughput?

A. Turn off RTS/CTS

B. Move all of the clients closer to the access point

C. Turn up the power on the access point

D. Purchase another access point and co-locate both

together

QUESTION 11

11. 802.11b devices use what type of

modulation at 11 Mbps?

A. BPSK

B. DPSK

C. QPSK

D. CCK

QUESTION 12

12. 802.11a devices use what type of

modulation at 24 Mbps?

A. BPSK

B. 16QAM

C. OFDM

D. CCK

QUESTION 13

13. If the sending station on a wireless LAN

does not receive an ACK, the sending station

assumes which one of the following?

A. The receiving station is sleeping

B. The receiving station is a hidden node

C. There was a collision

D. That RTS/CTS is turned on

QUESTION 14

14. Modulation is which of one of the following?

A. The process by which digital data is modified to

become RF data

B. The process of adding data to a carrier by

altering the amplitude, frequency, or phase of the

carrier in a controlled manner

C. The process of propagating an RF signal through

the airwaves

D. The means by which RF signals are received and

processed by RF antennas

QUESTION 15

15. Which one of the following is not part of a

superframe?

A. Beacon

B. Beacon Free Period

C. Contention Free Period

D. Contention Period

QUESTION 16

16. A superframe is used when which of the

following is true? Choose all that apply

A. The access point has been configured for point

coordination function mode

B. When beacons are disabled in the access point

C. The wireless clients have been configured to

announce to the access point that they are pollable

D. The access point has been configured for

distributed coordination function mode

QUESTION 17

17. What is the purpose of the superframe?

A. To increase the throughput of all wireless LANs

B. To ensure QoS for all voice and video

applications running on wireless LANs

C. To ensure that PCF- and DCF-mode clients do

not communicate within the same wireless LAN

D. To allow fair co-existence between PCF- and

DCF- mode clients on the network

QUESTION 18

18. The acronym CCA stands for which one of

the following?

A. Close Client Association

B. Clear Current Authentication

C. Clear Channel Assessment

D. Clean Channel Association

E. Calculate Clear Assessment

QUESTION 19

19. The Network Allocation Vector (NAV) acts

as:

A. A timer on the station

B. A navigational feature for RF signal

propagation

C. A location discovery tool for wireless LANs

D. A tool for allocating the bandwidth of a

wireless LAN

QUESTION 20

20. Using RTS/CTS allows wireless stations to

do which of the following?

A. Broadcast their intent to send data across the

network to the receiving station

B. Send their packets across the network at the

maximum rated speed of the network

C. Eliminate hidden nodes on the network

D. Diagnose and reduce high overhead between

stations