CWAP PW0-270 問題集

質問 1：
ABC Company's WLAN administrator is getting complaints from one user that his WLAN throughput is sluggish compared to other users in his area. The administrator takes his diagnostics laptop, which has a wireless protocol analyzer installed, to the area where the complaining user works. The administrator uses the PING utility to test connectivity from the complaining user's wireless client station to another wireless client station across the closest access point, while capturing the wireless frames. The administrator sees what is displayed in this screenshot.

From this screenshot, which statements can you conclude to be TRUE that are related to the complaining user's throughput problem? (Choose 2)
A. The complaining user's wireless client station should be using RTS/CTS as a protection mechanism, but it is not.
B. The complaining user's station is retransmitting fragments many times likely due to nearby RF interference.
C. The complaining user's WLAN client utilities are configured with a small fragmentation threshold.
D. The access point is not signaling for protection (Protection = no) in the Beacons, but it should be.
E. The access point and other stations are using ERP-OFDM modulation, and the complaining user's wireless client station is using HR/DSSS modulation.
正解：C,E

質問 2：
As shown in the exhibit, a spectrum analyzer has measured both 802.11 and non-802.11 RF transmissions in the 2.4 GHz band. The exhibit shows a continuous video transmitter near channel
5.Based upon the exhibit,

what impact does the video transmitter have on WLAN operations throughout the band?
A. The video transmitter has made no impact on WLAN operation in the band.
B. The video transmitter is preventing all WLAN transmissions in the band.
C. The video transmitter is preventing WLAN operation on channel 6, and has only a minor impact on channels 1 and 11.
D. The video transmitter is preventing all WLAN transmissions on channel 6, and its impact on channels 1 and 11 is severe.
正解：C

質問 3：
Given: Before installing a Wi-Fi network, ABC Company performed a spectrum analysis looking for problems. The 2.4 GHz RF spectrum looked like Image-A. After installing an ERP WLAN, ABC Company performed another spectrum analysis during business hours. The 2.4 GHz RF spectrum then looked like Image-B close to an AP on channel 1.

Now the 2.4 GHz RF spectrum looks like Image-C and access points and clients can no longer communicate on channel 1. What is happening on channel 1?
A. Detection of a DFS radar event has discontinued 802.11 operation on channel 1, but the access point's Channel Switch Announcement frame cannot be sent due to the presence of radar.
B. Stronger transmissions from licensed 2.4 GHz users, such as HAM operators, are compressing the transmissions from the channel 1 access points into the lower portion of the band.
C. A high-power, narrowband RF interference source on channel 1 is causing the CCA energydetects(ED) function on 802.11 devices to indicate a busy medium because the signal source is above the ED threshold.
D. The access point's antenna connectors have been tampered with, causing "spike and shear" RF transmissions that are not compatible with the OFDM PHY format. For that reason, client devices cannot receive the AP's transmissions without error.
E. The shape of the signals in images B and C indicates that a licensed user in this frequency range has enabled the "guard bands" in an effort to restrict local interference with other systems.
正解：C

質問 4：
Given the frame capture and the decode shown,

after which Beacons in the list shown (as indicated by the frame number in the leftmost column) would multicast traffic have been sent in this infrastructure BSS if multicast traffic had been queued for transmission at the access point? (Choose 2)
A. frame number 51
B. frame number 55
C. frame number 57
D. Framenumber 49
E. frame number 50
F. frame number 54
G. frame number 53
正解：A,B

質問 5：
In an HT WLAN in which a delayed Block Ack policy is set up, what should result when an ACK frame is not received by the originator in response to a Basic BlockAckReq?
A. All frames within that block must be retransmitted by the originator.
B. The last frame within that block must be retransmitted by the originator.
C. The BlockAckReq must be retransmitted by the originator.
D. Nothing. No ACK is expected in response to a Basic BlockAckReq.
正解：C

質問 6：
What is the purpose of a PHY preamble?
A. It indicates to the PHY the modulation that shall be used for transmission (and reception) of the PSDU.
B. It provides a cyclic redundancy check (CRC) for the receiving station to validate that the PLCP header was received correctly.
C. It communicates important information about the PSDU's length, rate, and upper layer protocol-related parameters.
D. It provides the receiver(s) with an opportunity for RF channel synchronization prior to the start of the PLCP header.
正解：D