Question 1

Why are DSSS channels more susceptible to narrowband interference than FHSS channels?
A)A DSSS channel is much larger and wider.
B)FHSS systems only use one frequency at a time, so the narrowband interference must be on the same exact frequency at the same time.
C)Information is transmitted one frequency at a time instead of simultaneously transmitting over the entire band.
D)FHSS systems simply avoid the frequency on which narrowband interference occurs.

Accepted Answer

The reason that DSSS channels are more susceptible to narrowband interference than FHSS channels is that FHSS systems only use one frequency at a time, so the narrowband interference must be on the same exact frequency at the same time.
Key Takeaway: DSSS combines the information signal with a spreading signal having much wider bandwidth. The net modulation signal effectively handles the wide bandwidth of the spreading signal. With FHSS the information is left unchanged and a carrier of varying frequency is directly modulated. This approach is a collection of conventional narrowband signals, hence FHSS is less susceptible to narrowband interferece

Question 2

Which of the following aspects is not described by the IEEE and OpenAir standards regarding FHSS systems?
A)Allowable levels of interference
B)Frequency bands that may be used
C)Hop sequences
D)Dwell times

Accepted Answer

IEEE and OpenAir standards do not describe allowable levels of interference regarding FHSS systems.
Key Takeaway: Both OpenAir and 802.11 standards define all parameters necessary for an equipment to function. These specifications include dwell times, data rates, data rate fallback functionality, frequency hop patterns or channels, and frequency bands to be used.

Question 3

Which of the following is true regarding some FHSS systems that operate at 2.4 GHz and a speed of 3 Mbps?
A)IEEE 802.11 compliancy
B)Non-interoperable with other FHSS systems
C)OpenAir compliancy
D)Backward compatibility with 900 MHz systems

Accepted Answer

Some FHSS systems that operate at 2.4 GHz and a speed of 3 Mbps are non-interoperable with other FHSS systems.
Key Takeaway: FHSS systems that can transmit data at 3 Mbps may or may not have the ability to slow their data rate to 2 Mbps or 1 Mbps as specified by the 802.11 standard. These systems comply with the IEEE standard if they transmit at 2 Mbps and 1 Mbps, or the OpenAir standard if they could transmit at 1.6 Mbps and 800 kbps. When they transmit at any other speeds, they are not compliant with either standard.

Question 4

Which of the following can you use to increase the throughput in an FHSS system?
A)Shortening the dwell time and lengthening the hop time
B)Shortening the dwell time and shortening the hop time
C)Lengthening the dwell time and shortening the hop time
D)Lengthening the dwell time and lengthening the hop time

Accepted Answer

Throughput can be increased by lengthening the dwell time and shortening the hop time.
Key Takeaway: Lengthening the dwell time decreases the amount of hopping. Shortening the hop time decreases overhead. Hence, increasing the dwell time increases throughput. Dwell time is the time period before which data hops to the next channel in the sequence. FHSS devices are limited to a dwell time of 400 microseconds.

Question 5

Which of the following best defines a noise floor?
A)The noise generated as a result of foot traffic
B)The level of RF noise in the wireless LAN environment
C)A fixed level of noise of -100 dBm in a wireless LAN
D)The level of noise at which a wireless LAN starts working

Accepted Answer

Noise floor is the level of RF noise in the wireless LAN environment.
Key Takeaway: Noise floor is a mixture of all of the background RF radiation found in the environment surrounding the wireless system in use. RF signals must be higher than the noise floor to be detectable by a receiver.

Question 6

You plan to use a Basic or Extended service set. Which of the power management features populate the traffic indication map, or TIM, with station information?
A)Power-save polling mode
B)Continuous aware mode
C)Continuous power mode
D)Power-aware polling mode

Accepted Answer

The Power-save polling mode populates the traffic indication map, or TIM, with station information when using a Basic or Extended service set.
Key Takeaway: When a station is not sleeping, the access point does not need to buffer packets destined to that station. If a station is sleeping, the access point should buffer its packets so that the packets are not lost. TIM is used to notify stations using power-save polling, or PSP, mode that they have packets buffered at the access point. Client stations use power-save poll frames to notify the access point to send the buffered packets.

Question 7

Which of the following statements is true regarding power management features?
A)Using the Power Save Polling mode allows a wireless client to sleep
B)Using the Power Save Polling mode forces a wireless client to accept an access point's polling
C)Using the Power Save Polling mode allows a wireless client to accept packets while asleep
D)Using the Power Save Polling mode does not cause overhead in an ad hoc network

Accepted Answer

The statement that is true is using the power save polling mode allows a wireless client to sleep.
Key Takeaway: Power Save Polling mode allows wireless clients to sleep. Sleeping clients cannot receive packets, so they are buffered at the access point. When the Power Save Polling mode is used, it creates an additional overhead on the wireless network segment.

Question 8

Which of the following statements is true if a station does not receive an ACK after it transmits a data frame and waits a SIFS?
A)The receiving station will not receive the data.
B)The transmitting station may not have sent the data.
C)The transmitting station will wait an additional SIFS to receive the ACK.
D)The transmitting station will send a retransmit notification.

Accepted Answer

The statement that is true is the transmitting station will send a retransmit notification.
Key Takeaway: Since the transmitting station has not received the ACK, the transmitting station will attempt to retransmit the data frame. The transmitting station will also send a retransmit notification.

Question 9

Which of the following is a function of the beacon frame?
A)Load balancing all clients across multiple access points
B)Broadcasting the SSID to enable clients to connect to the access point
C)Asynchronizing the time between the access point and clients
D)Allowing client authentication with the access point when using Shared Key authentication

Accepted Answer

Beacon frames broadcast the SSID to enable clients to connect to the access point.
Key Takeaway: Sending time synchronization and SSID information are two of the main functions of the beacon management frame. Other functions of the beacon frame include sending TIM, supported communication rates, and FH/DS parameters.

Question 10

Which of the following results when the Power Save Polling mode is used?
A)Increased throughput on the network due to less overhead traffic
B)Intermittent throughput on the network due to more overhead traffic
C)Network traffic is not affected by using PSP.
D)Longer battery life on the clients that use PSP

Accepted Answer

Power Save Polling mode enables longer battery life on clients that use PSP.
Key Takeaway: The key advantage of using PSP mode is prolonged battery life on mobile stations. The drawback of using PSP is the additional overhead of PSP frames on the network.

Question 11

Which of the following does a client station do to indicate that it is using power save mode?
A)It transmits a frame to the access point, with the Sleep field set to 1.
B)It transmits a frame to the access point, with the Power Management field set to 1.
C)The access point determines when the client station uses power save mode using DTIM.
D)It does nothing. Power Save mode is set by default.

Accepted Answer

The client station transmits a frame to the access point with the Power Management field set to 1.
Key Takeaway: When the client station transmits a frame with the Power Management field set to 1, it is enabling the Power Save mode. The DTIM only notifies clients to stay awake in preparation for a multicast or broadcast.

Question 12

Which of the following statements is true when transmitting fragmented frames in an environment where frame retransmission is common?
A)The overall number of bits transmitted will always be greater than if fragmentation was disabled.
B)The overall number of bits transmitted will always be less than if fragmentation was disabled.
C)Data throughput may decrease.
D)Data throughput will remain constant.

Accepted Answer

In an environment where frame retransmission is common, the data throughput may decrease.
Key Takeaway: In a noisy environment, the fragmented frames contain more bits than un-fragmented frames. If frames need to be retransmitted, it is possible that the overall number of bits transmitted is actually less than if the frames had not been fragmented. In such a case, the throughput may increase or decrease, depending upon how many frames are retransmitted.

Question 13

Which of the following specifies why passive scanning is used in a wireless LAN?
A)To allow clients to authenticate with an access point
B)To reduce the time taken by clients to locate and associate to access points when they are roaming
C)To allow clients to actively search for any access points within range
D)To determine which bridge the client will connect to

Accepted Answer

Passive scanning is used to reduce the time taken by clients to locate and associate to access points when they are roaming.
Key Takeaway: A client station constantly monitors beacons sent by all access points in its vicinity. It decides which access point would be the best candidate for re-association if the current link should fail. Time is saved in re-association, making roaming a more seamless process.

Question 14

Which of the following will cause the station to stay awake and wait to receive data if a BSS station is in Power Save mode?
A)An ATIM sent to the station
B)A broadcast that does not contains a DTIM
C)Sending a frame with the More Data field set to 1
D)A TIM that contains the stations AID

Accepted Answer

A TIM that contains the station's AID will cause the station to stay awake and wait to receive data if a BSS station is in Power Save mode.
Key Takeaway: An ATIM will cause a station to stay awake in an IBSS station only. A DTIM notifies the station that it must stay awake and wait for a multicast or broadcast frame. If a station receives a frame with the More Data field set to 1, the AP has additional data for the station and the station is not allowed to go to sleep. If the TIM contains the station AID, the station must stay awake to receive the data that AP has cached.

Question 15

Which of the following best defines the term Hopping used in Frequency Hopping wireless LAN systems?
A)Switching throughput speeds between 11 Mbps to 5.5 Mbps
B)FHSS feature where the carrier frequency is changed
C)Change that occurs as a result of the RF signal getting weaker
D)Change in transmission technology from FHSS to DSSS

Accepted Answer

Hopping is a FHSS feature where the carrier frequency is changed.
Key Takeaway: Frequency hopping is a modulation technique used in spread spectrum signal transmission. Hopping periodically switches the transmission frequencies during radio transmission to minimize unauthorized interception or jamming. It also is known as frequency- hopping code division multiple access, or FH-CDMA. When a FHSS system hops, both the transmitter and receiver systems change the carrier frequency in a synchronized fashion.

Question 16

Which of the following statements is true if an RF signal is considered as a spread spectrum?
A)The system sending the signal uses infrared technology.
B)The power required to send information is significantly greater.
C)The bandwidth used is much wider than that required to send information.
D)The bandwidth used is much less than that used to send information.

Accepted Answer

When an RF signal is considered as a spread spectrum, the bandwidth used is much wider than that required to send information.
Key Takeaway: Spread spectrum transmitters spread a data signal out over a wide band of frequencies. They do this by using many symbols per bit for redundancy and using very low power.

Question 17

An 802.11g network has the protected mode enabled. Which of the following provides the best throughput with the least likelihood of retransmissions?
A)AP using RTS/CTS and stations using RTS/CTS
B)AP using RTS/CTS and stations using CTS-to-Self
C)AP using CTS-to-Self and stations using RTS/CTS
D)AP using CTS-to-Self and stations using CTS-to-Self

Accepted Answer

In an 802.11g network that has the protected mode enabled, AP using CTS-to-Self and stations using RTS/CTS provides the best throughput with the least likelihood of retransmissions.
Key Takeaway: Because all stations in a BSS are able to hear the AP, CTS-to-Self is the most efficient method for the AP to perform NAV distribution. It is possible for two stations to be hidden from each other while both are part of the same BSS. In this case, RTS/CTS is the best method for performing NAV distribution.

Question 18

Which of the following specifies why Shared Key authentication is considered a security risk?
A)Access points transmit unencrypted challenge text and receive the same challenge text encrypted with the WEP key
B)Keys are shared broadcasted to all network nodes
C)A hacker can sniff the keys with a protocol analyzer
D)All computers use identical WEP keys

Accepted Answer

Shared Key authentication is considered a security risk because an access point transmits unencrypted challenge text and receives the same challenge text encrypted with the WEP key.
Key Takeaway: Because the plaintext challenge and the encrypted plaintext challenge are transmitted in the clear in sequence, a hacker could easily obtain both with a protocol analyzer. These challenges can be used to yield the WEP key, which could then be used for real-time decryption of data packets on the network.

Question 19

When should you configure the Continuous Aware Mode on wireless LAN clients?
A)When portable laptop station users need the ability to roam away from power sources
B)When desktop stations are not frequently moved from their permanent location
C)When PDAs have limited battery life
D)When laptop computers do not remain connected to a power source

Accepted Answer

You should configure the Continuous Aware Mode on wireless LAN clients when desktop stations are not frequently moved from their permanent location.
Key Takeaway: In the Continuous Aware Mode, the radio receiver is always on and consuming power. It is only recommended for stations that have a continuous power source. This mode improves the performance of both the station and the network.

Question 20

Which of the following is a disadvantage associated with using a number of access points in the Repeater Mode in a series?
A)Throughput will be reduced to unacceptable levels
B)All access points should be physically connected to the network.
C)Users attached to the repeater access point will experience high latencies.
D)Legacy serial devices will not be able to communicate with the root access point.

Accepted Answer

The disadvantage associated with using a number of access points in the Repeater Mode in series is that users attached to the repeater access point will experience high latencies.
Key Takeaway: A WLAN repeater does not physically connect by wire to any part of the network. Instead, it receives 802.11 frames from an access point, an end-user device, or another repeater and retransmits the frames. A downside of wireless repeaters is that they reduce throughput on the WLAN. Because the repeater must receive and retransmit each frame on the same RF channel, it effectively doubles the number of frames that are sent. This problem compounds when using multiple repeaters because each repeater will duplicate the number of frames sent. This latency may make it impossible to use real-time audio or video applications.

Quiz 1: Certified Wireless Network Administrator (CWNA)

Why are DSSS channels more susceptible to narrowband interference than FHSS channels?

Which of the following aspects is not described by the IEEE and OpenAir standards regarding FHSS systems?

Which of the following is true regarding some FHSS systems that operate at 2.4 GHz and a speed of 3 Mbps?

Which of the following can you use to increase the throughput in an FHSS system?

Which of the following best defines a noise floor?

You plan to use a Basic or Extended service set. Which of the power management features populate the traffic indication map, or TIM, with station information?

Which of the following statements is true regarding power management features?

Which of the following statements is true if a station does not receive an ACK after it transmits a data frame and waits a SIFS?

Which of the following is a function of the beacon frame?

Which of the following results when the Power Save Polling mode is used?

Which of the following does a client station do to indicate that it is using power save mode?

Which of the following statements is true when transmitting fragmented frames in an environment where frame retransmission is common?

Which of the following specifies why passive scanning is used in a wireless LAN?

Which of the following will cause the station to stay awake and wait to receive data if a BSS station is in Power Save mode?

Which of the following best defines the term Hopping used in Frequency Hopping wireless LAN systems?

Which of the following statements is true if an RF signal is considered as a spread spectrum?

An 802.11g network has the protected mode enabled. Which of the following provides the best throughput with the least likelihood of retransmissions?

Which of the following specifies why Shared Key authentication is considered a security risk?

When should you configure the Continuous Aware Mode on wireless LAN clients?

Which of the following is a disadvantage associated with using a number of access points in the Repeater Mode in a series?