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66.
Which two channels could be used so that the access points do not interfere with each other
in an 802.11b wireless network? (Choose three.)
- A.Channel 1 and channel 5
- B.Channel 3 and channel 9
- C.Channel 6 and channel 11
- D.Channel 2 and channel 8
- E.Channel 4 and channel 7
- Answer & Explanation
- Report
Answer : [B, C, D]
Explanation :
Explanation :
| 802.11b channels need to be separated by at least fi ve channels or 25 MHz to be considered non-overlapping. Channels 3 and 9 are separated by six channels, channels 6 and 11 are separated by fi ve channels, and channels 2 and 8 are separated by six channels. All of these scenarios are nonoverlapping channels. |
67.
Which network access method attempts to avoid collisions?
- A.CSMA/CA
- B.CSMA/CD
- C.CSMA/CR
- D.CSMA/DSSS
- E.None of the other answers are correct.
- Answer & Explanation
- Report
Answer : [A]
Explanation :
Explanation :
| CSMA/CA uses collision avoidance. CSMA/CD uses collision detection. CSMA/ CR and CSMA/DSSS do not exist. |
68.
DSSS uses which spreading code at 1 Mbps?
- A.Barker
- B.CCK
- C.DBPSK
- D.DQPSK
- Answer & Explanation
- Report
Answer : [A]
Explanation :
Explanation :
| DSSS uses Barker code at 1 Mbps. CCK is for 5.5 Mbps. DBPSK and DQPSK are modulation technologies, not spreading codes. |
69.
FM radio stations use what type of RF communication?
- A.High power, narrow bandwidth
- B.High power, wide bandwidth
- C.Low power, narrow bandwidth
- D.Low power, wide bandwidth
- Answer & Explanation
- Report
Answer : [A]
Explanation :
Explanation :
| FM radio stations use narrowband communication, which is high power and narrow frequency. WLANs use spread-spectrum technology, which is low power and wide frequency. |
70.
An HR/DSSS channel is how wide?
- A.1 MHz
- B.20 MHz
- C.22 MHz
- D.40 MHz
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| HR/DSSS channels are 22 MHz wide. FHSS uses 1 MHz subcarrier frequencies. OFDM, ERP-OFDM, and HT-OFDM use 20 MHz–wide channels, and HT-OFDM can also use 40 MHz–wide channels. |
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