Faculty of Computer Science & Engineering

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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 DCFmode 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
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D. Clean Channel Association
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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

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