CWAP CWAP Certifications PW0-270 Questions & Answers

• Question 11:

  ABC Company is having VoWiFi latency problems on their 802.11g WLAN. A wireless administrator has noticed in the phone's client utilities software that the MAC CRC Error count is higher on stations with problems than on those client stations without problems.

  A high MAC CRC Error count is attributable to which of the following? (Choose 3)

  A. High collision rates due to dense population of voice stations and no admission control

  B. Two access points with overlapping coverage on a single channel

  C. High multipath conditions due to an RF environment with highly reflective materials

  D. 2.4 GHz ISM band interference from sources such as wireless video cameras and analog phones

  E. Co-located DCF and EDCA access points that are using non-overlapping 2.4 GHz channels

  F. Dynamic Rate Switching algorithms that decrease data rates for latency-sensitive applications

  Correct Answer: ACD

• Question 12:

  While at a government-operated facility, you are attempting to troubleshoot a WLAN performance problem using a wireless protocol analyzer. When you start capturing frames, you see a proprietary layer 2 protocol running over the ERP network as shown in this screenshot. The facility's WLAN administrator confirms that this protocol is proprietary and used for both data encryption and compression.

  

  How will this information affect the steps you take to troubleshoot performance problems on this WLAN?

  A. The proprietary encryption protocol will have no effect on your troubleshooting steps because the wireless protocol analyzer can still decode the PLCP and MAC headers of Data frames. This situation is essentially no different than troubleshooting a WLAN that uses WPA2-Personal.

  B. Troubleshooting will be somewhat limited because only part of the information needed for performance measurements by the analyzer is encrypted. Each Data frame's MAC header will be encrypted, but the PLCP header can still be decoded successfully.

  C. As long as you load the proprietary software codec onto your analyzer computer, you will be able to see all of the Data frame information fully decoded. Loading the proprietary software codec will allow you to troubleshoot the WLAN as though no encryption were in use.

  D. In order to troubleshoot performance problems on a network using proprietary encryption protocols like this one, you must use a wireless protocol analyzer that has integrated support for the protocol in use.

  Correct Answer: A

• Question 13:

  As it relates to a spectrum analyzer, complete the following sentence.

  The ____________ plot always displays the percentage of time (shown on the Y axis) that the overall RF power is a certain specified threshold (of amplitude) above the noise floor for a given frequency range (shown on the X axis).

  A. Real-Time FFT

  B. Swept Spectrogram

  C. FFT Duty Cycle

  D. Interferer Count

  E. SNR

  Correct Answer: C

• Question 14:

  Using the exhibit as a reference,

  

  which spectrum plots display, in real time, the value of RF amplitude as a function of radio frequency?

  A. 1 and 2

  B. 1 and 3

  C. All of the plots

  D. 1, 3, and 4

  E. 3 and 4

  Correct Answer: B

• Question 15:

  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 is preventing WLAN operation on channel 6, and has only a minor impact on channels 1 and 11.

  B. The video transmitter has made no impact on WLAN operation in the band.

  C. The video transmitter is preventing all WLAN transmissions in the band.

  D. The video transmitter is preventing all WLAN transmissions on channel 6, and its impact on channels 1 and 11 is severe.

  Correct Answer: A

• Question 16:

  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. 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.

  B. 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.

  C. 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.

  D. 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.

  E. 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.

  Correct Answer: B

• Question 17:

  What types of wireless systems are illustrated?

  

  A. An ERP IEEE 802.11 system using channel 6 and Bluetooth v1.2 discovery

  B. A Bluetooth v2.0 file transfer and a 40 MHz HT AP on channels 11, 7 (primary, secondary)

  C. A 2.4 GHz cordless phone on channel 14 and a wireless RFID reader

  D. An 802.11 HR/DSSS system using channel 2 and a digital FHSS phone

  Correct Answer: A

• Question 18:

  Given: The graphic is taken from a spectrum analyzer.

  

  What types of RF transmitters are illustrated?

  A. An IEEE 802.11 HR/DSSS security camera on channel 6 and an RFID tag

  B. A Bluetooth headset and a narrowband RF jamming device

  C. A 2.4 GHz cordless phone and an OpenAir FHSS system

  D. A 20 MHz HT IEEE 802.11 system using channel 1 and a microwave oven

  Correct Answer: D

• Question 19:

  As it pertains to HT L-SIG TXOP Protection, what statement is true?

  A. Support for L-SIG TXOP Protection is indicated by HT stations in the L-SIG field of the PLCP header of HT-mixed format frames.

  B. Support for L-SIG TXOP Protection is indicated in the HT Capabilities Info field of (re)association request frames sent by ERP, OFDM, and HT-OFDM stations.

  C. An L-SIG TXOP protected frame exchange sequence always begins with an RTS/CTS or a CTS-to- Self.

  D. L-SIG TXOP Protection is specified for the purpose of protecting OFDM (802.11a/g) and HT- OFDM (802.11n) transmissions from HR/DSSS stations.

  Correct Answer: C

• Question 20:

  When a client station operating under EDCA sends an RTS frame and NAV protection is desired for only the first or sole frame in the TXOP, the duration field will contain an amount of time, measured in microseconds, equal to which of the following?

  A. 1 RTS, 2 ACK, 1 DATA, 4 SIFS

  B. 1 CTS, 1 ACK, 1 DATA, 3 SIFS

  C. 1 RTS, 1 ACK, 1 DATA, 2 SIFS, 1 DIFS

  D. 1 RTS, 1 CTS, 2 ACK , 1 DATA, 4 SIFS

  E. 1 CTS, 2 ACK, 1 DATA, 2 SIFS

  F. The entire duration of the TXOP

  Correct Answer: B