Wireless Technologies Questions and Answers

Answer: C

Correct answer: 23

802.11h extends 802.11a with dynamic frequency selection and transmit power control, which allow the additional 5 GHz channels reserved for radar to be used safely. That takes the count from twelve to twenty-three. The amendment was written for European regulatory requirements and is what made the extended band usable at all.

Answer: B

Correct answer: About 175 feet

At its lowest rate 802.11a reaches about 175 feet - half the 350 feet of 802.11b at its lowest rate. The pattern holds at every rate: for the same modulation, the 5 GHz signal covers roughly half the distance of the 2.4 GHz one.

Answer: A

Correct answer: 3

The 2.4 GHz band holds eleven channels in North America but each is 22 MHz wide against a 5 MHz spacing, so adjacent channels overlap heavily. Only channels 1, 6 and 11 are far enough apart not to interfere. That figure of three is the fundamental constraint on 2.4 GHz deployment: cells must be laid out so that no two neighbours share a channel.

Answer: C

Correct answer: 2.4GHz

802.11b uses the 2.4 GHz ISM band, which it shares with 802.11g, Bluetooth, cordless telephones and microwave ovens - the source of most of the interference that band suffers. As with the 802.11a item, the two options quoted in Gbps are rates rather than frequencies and can be discarded on units.

Answer: B

The split-MAC architecture allows the splitting of 802.11 protocol packets between the Cisco LWAPP-based AP, which handles real-time portions of the protocol, and the WLAN controller, which handles those items that are not time sensitive.

Answer: C

Correct answer: About 150 feet

802.11b reaches about 150 feet at its maximum 11 Mbps. It has the longest full-rate range of the three, because its low data rate uses a robust modulation that tolerates a weaker signal - and because 2.4 GHz penetrates obstacles better than 5 GHz.

Answer: D

Correct answer: About 350 feet

At its lowest rate of 1 Mbps, 802.11b reaches about 350 feet. Range and rate trade against each other continuously: as a client moves away the signal weakens, the radio falls back to a more robust modulation, and the throughput drops. The 150 feet quoted elsewhere in this topic is the distance at the full 11 Mbps.

Answer: B

Correct answer: About 90-100 feet

802.11g reaches about 90 to 100 feet at 54 Mbps. It sits between the other two: better than 802.11a’s 65 to 75 feet because 2.4 GHz propagates further, but well short of 802.11b’s 150 feet because holding 54 Mbps demands a much stronger signal than holding 11.

Answer: C

Correct answer: About 300 feet

At its lowest rate 802.11g reaches about 300 feet, a little short of 802.11b’s 350. The two share a band, so the difference lies in the modulation each falls back to rather than in propagation, and the ordering of the three standards is the same at every rate: b furthest, g next, a shortest.

Answer: A

Correct answer: That you have more than one access point and they are in the same SSID connected by a distribution system.

An Extended Service Set joins two or more basic service sets under one SSID, linked by a distribution system - usually the wired network. Because the SSID is shared, a client can roam between the access points without reassociating to a different network. Separate SSIDs would be separate networks, and the physical placement of the access points is not what defines the term.