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