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Combo with "Chapter 6 Wireless LAN"

Pataasin ang iyong marka sa homework at exams ngayon gamit ang Quizwiz!

Understand the inverse square law for attenuation. Be able to solve a problem such as (228): If the signal strength at 10 meters is 40 milliwatts (mW), what will the strength be at 20 meters? (answer: 10 mW)

(1/r^2) -- for simple problems S2 = S1(r1/r2)^2 -- for problem given Note: r is the meters for the first and second signal

There is an access point that serves eight wireless hosts. On how many channels will these devices transmit and receive during the course of an hour or two?

If the lowest frequency in a channel is 1.22 MHz and the highest frequency is 1.25 MHz, what is the channel bandwidth? (Use proper metric notation.) [231]

1.25 - 1.22 = 0.03 MHz or 30 kHz

The 5 GHz band usually supports about ________ non-overlapping 20 MHz channel(s).

A wireless host sends a packet to a server on the company's wired Ethernet LAN via an access point. How many frames will be involved in this one-way transmission?

For each, compare channel bandwidth and the number of possible channels. [250]

2.4 802.11g use 20 MHz and 3 Channels. 802.11n Single Band has 20 MHz and 3 Channels 802.11n Dual Band uses 40 MHz has 3 in 2.4 GHz , 12 (US) in the 5 GHz 802.11ac has 80 MHz and 160 MHz uses 6 in 80 MHz and 3 Channels in 160 MHz 802.11ad uses 60 MHz and 3 Channels in the US & 4 in Europe. , 5, and 60 GHz band

How many non-overlapping 20 MHz channels does the 2.4 GHz band support? [235-237]

2.4 GHz, three possible non-overlapping 20 MHz 802.11 channels, which are centered at Channels 1, 6, and 11.

In what two unlicensed bands does 802.11 operate? [235-237]

2.4 and 5 GHz

What frequency band or bands do 802.11g, 802.11n single band, 802.11n dual band, 802.11ac, and 802.11 ad use? [250]

2.4, 5, 60 GHz band

In 802.11g, channel bandwidth usually is ________.

20 MHz

The 2.4 GHz band supports ________ possible non-overlapping 20 MHz channel(s).

Convert 3.4 MHz to a number without a metric prefix. [226]

3400000 Hz

At what range of frequencies do most wireless systems operate? [226]

500 megahertz 10 gigahertz

In the 5 GHz band, how many channels can you have with 802.11ac with 80 GHz channels?

We use the terms Wi-Fi and ________ interchangeably in this book.

802.11

Wi-Fi Standards come from the ________ Working Group.

802.11

What 802 working group creates 802.11 standards? [225]

802.11 Working Group

Today, Wi-Fi sales are dominated by ________.

802.11ac

Which of the following is the newest Wi-Fi standard?

802.11ac

Which can bring gigabit speeds to clients? [247-249]

802.11ac & 802.11ad

What is the maximum rated speed for each standard? [247-249]

802.11g = 54 Mbps 802.11n Single Band = 100 to 600 Mbps 802.11n Dual Band = 100 to 600 Mbps 802.11ac = 433 Mbps to 6.9 Gbps 802.11ad = 7 Gbps

What is backward compatibility? [254]

802.11g access point. In the same way, an 802.11n access point must be able to work with an older 802.11g access point. Of course, when an 802.11n device works with an 802.11g device, the transmission can take place only at 802.11g speeds. The 802.11n device must drop back to 802.11g operation. This Panko, Raymond; Panko, Julia (2012-10-09). Business Data Networks and Security (9th Edition) (Page 254). Prentice Hall. Kindle Edition.

Of the four 802.11 transmission standards summarized in this section, which are full standards, and which are only draft standards?

802.11g and 802.11n are full standards 802.11ac and 802.11ad are still draft standards.

Compare maximum speeds for 802.11g and 802.11n and the maximum distances at which each standard can provide these speeds. [247-249]

802.11g, the maximum distance and speed are 30 m and 54 Mbps. 802.11n, distance and speed are much longer and faster at 70 m and 100-600 Mbps respectively.

The standard for roaming among access points is ________.

802.11r

1) Wireless network standards operate at ________. A) the data link layer B) the internet layer C) Both A and B D) Neither A nor B

10) Attenuation with distance is faster with ________. A) radio transmission B) UTP transmission C) Both A and B D) Neither A nor B

14) What propagation problem becomes worse as frequency increases? A) Absorptive attenuation. B) Electromagnetic interference. C) Both A and B D) Neither A nor B

19) To handle multiple conversations in radio transmission, you use multiple ________. A) channels B) frequencies C) service bands D) wires

2) Wireless network standards come from ________. A) OSI B) TCP/IP C) Both A and B D) Neither A nor B

20) Signals usually ________. A) spread over a range of frequencies B) travel at a single frequency

22) To transmit very rapidly in RADIO, you need ________. A) wide bandwidth B) narrow bandwidth C) single-frequency transmission D) single-mode transmission

23) Channels with wide bandwidths are called ________ channels. A) broadband B) modulated C) multimode D) full-duplex

27) In the Shannon Equation, if you quadruple the bandwidth in a channel while the signal-to-noise ratio remains the same, you can transmit ________. A) about 4 times as fast B) at the same speed, but more reliably C) Log2(1+4) times as fast D) Log2(1+1/4) times as fast

29) If a radio transmission is easily blocked by obstacles, then you need to maintain ________. A) a clear line of sight B) spread spectrum transmission interference C) broadband transmission D) deep transmission

3) Wireless LAN standards are created by the ________ Working Group. A) 802.11 B) 802.1 C) 802.3 D) 802.3W

30) WLANs normally use ________. A) unlicensed bands B) licensed bands

31) In unlicensed bands, ________. A) you can use radios wherever you please B) you can prevent nearby businesses from setting up access points in the same channel C) Both A and B D) Neither A nor B

32) Interference is minimized in ________. A) licensed bands B) unlicensed bands

34) In 802.11, channel bandwidth usually is ________. A) 20 MHz B) 40 GHz C) 40 MHz D) 20 GHz

35) Which unlicensed band is defined the same way in most countries around the world? A) 2.4 GHz. B) 5 GHz. C) Both A and B D) Neither A nor B

36) Which unlicensed band provides greater propagation distance for a given level of power? A) 2.4 GHz. B) 5 GHz. C) Both A and B allow about the same propagation distance.

39) Spread spectrum transmission is used in WLANs because ________. A) it is required by regulators B) it offers strong security C) Both A and B D) Neither A nor B

4) Wireless access points typically link wireless clients to ________. A) servers on the wired network B) wireless servers C) Both A and B

46) Access points take ________ from wireless devices and send them on to devices on the wired LAN. They also do the converse. A) packets B) frames C) Both A and B D) Neither A nor B

47) A wireless host sends a packet to a server on the company's wired Ethernet LAN via an access point. How many frames will be involved in this one-way transmission? A) 2 B) 1 C) 4 D) There will be one frame for each switch along the way.

48) An access point and the set of hosts it serves is called a(n) ________. A) BSS B) BSSID C) ESS D) None of the above

5) Wireless radio transmission usually is expressed in terms of ________. A) frequency B) wavelength C) Both A and B D) Neither A nor B

54) In an extended service set, each access point ________. A) must have the same SSID B) must have different SSIDs C) must have coordinated SSIDs D) None of the above

55) The standard for roaming among access points is ________. A) 802.11r B) 802.11s C) 802.11W D) None of the above

56) What happens if two nearby access points use the same channel? A) They will interfere with each other. B) They will be bonded for joint operation automatically. C) They will be bonded for joint operation automatically if they use CSMA/CA+ACK. D) They will be bonded for joint operation automatically if they use RTS/CTS.

57) There is an access point that serves eight wireless hosts. On how many channels will these devices transmit during the course of an hour or two? A) 1 B) 2 C) 7 D) 8

61) When a wireless NIC wishes to transmit, it listens for traffic. If there is traffic, it waits. If there is no traffic, it may transmit. A) Sometimes true. B) False. C) True.

64) CSMA/CA+ACK is ________. A) inefficient B) efficient

66) CSMA/CA+ACK usually is ________. A) required B) optional

67) Which of the following is usually optional in access point operation? A) CSMA/CA+ACK. B) RTS/CTS. C) Both A and B D) Neither A nor B

68) Which of the following is more efficient? A) CSMA/CA+ACK. B) RTS/CTS. C) Both are about equally efficient.

7) The other wireless device is far away in a known direction. You should use ________. A) a dish antenna B) an omnidirectional antenna C) Both A and B D) Neither A nor B

73) Which of the following brings gigabit speeds to clients? A) 802.11ac B) 802.11g C) 802.11n D) None of the above

74) For wireless backup, which of the following is adequate? A) 802.11ac B) 802.11g C) 802.11n D) All of the above

75) Which of the following uses OFDM? A) 802.11g B) 802.11ac C) Both A and B D) Neither A nor B

76) Wider channel bandwidth ________. A) decreases transmission speed B) allows more channels to be used in a service band C) Both A and B D) Neither A nor B

77) Which of the following can operate in the 5 GHz band? A) 802.11ac B) 802.11g C) Both A and B D) Neither A nor B

77) Which of the following can operate in the 5 GHz band? A) 802.11g B) 802.11ac C) Both A and B D) Neither A nor B

79) In the 60 GHz service band, ________. A) channel bandwidth can be very wide B) signals travel farther C) Both A and B D) Neither A nor B

8) Cellular telephony uses ________. A) a dish antenna B) an omnidirectional antenna C) Both A and B D) Neither A nor B

8) Cellular telephony uses ________. A) an omnidirectional antenna B) a dish antenna C) Both A and B D) Neither A nor B

82) MIMO ________. A) increases throughput B) lowers propagation distance C) Both A and B D) Neither A nor B

83) Beamforming can ________. A) direct signal strength at individual wireless hosts B) transmit multiple spatial data streams in the same channel C) Both A and B D) Neither A nor B

85) Traditional MIMO can ________ A) send multiple signals in the same channel B) send signals to two different clients at the same time C) Both A and B D) Neither A nor B

88) If more users move to an access point, this decreases ________. A) individual throughput B) aggregate throughput C) Both A and B D) Neither A nor B

91) If an 802.11n access point and an 802.11g client communicate, they communicate using ________. A) 802.11g B) 802.11n C) Either A or B D) Neither A nor B

94) Mesh networking in 802.11 is likely to use ________. A) only wireless devices B) wireless devices and the site's wired LAN C) Both A and B

95) The 802.11 standard for mesh networking is ________. A) 802.11m B) 802.11r C) 802.11ac D) None of the above

What is channel bandwidth? [231]

A channel also has a bandwidth. For instance, if the lowest frequency of an FM channel is 89.0 MHz and the highest frequency is 89.2 MHz, then the channel bandwidth is 0.2 MHz (200 kHz).

How can firms provide WLAN coverage throughout a large building? [225]

A firm can strategically place wireless access points judiciously throughout a building. In essence, the firm is creating a large 802.11 WLAN "cloud" .

What is a handoff in 802.11? [243]

A handoff is when a user moves to a closer access point.

77) Which of the following can operate in the 5 GHz band? A) 802.11ac B) 802.11g C) Both A and B D) Neither A nor B

A) 802.11ac

79) In the 60 GHz service band, ________. A) channel bandwidth can be very wide B) signals travel farther C) Both A and B D) Neither A nor B

A) channel bandwidth can be very wide

MIMO ________. A) increases throughput B) lowers propagation distance C) Both A and B D) Neither A nor B

A) increases throughput

If more users move to an access point, this decreases ________. A) individual throughput B) aggregate throughput C) Both A and B D) Neither A nor B

A) individual throughput

94) Mesh networking in 802.11 is likely to use ________. A) only wireless devices B) wireless devices and the site's wired LAN C) Both A and B

A) only wireless devices

What is a clear line-of-sight limitation? [234]

Absorption and shadow zone propagation problems are large. In addition, demand for channels and service bands in the golden zone is increasing rapidly.

Besides moving packets between wireless clients and the Ethernet network, what other control functions do access points have? [242]

Access points also control hosts as wells as assigning transmission power levels to hosts within its range and other supervisory chores.

What devices forward frames in a mesh network? [256]

Access points or wireless hosts

What is the purpose of the 802.11r standard? [243]

Access points to contact one another when it deals with roaming.

How does Wi-Fi Direct differ from the traditional way in which two wireless hosts communicate?[255]

Adhoc connection, no access point need and its simpler.

What is an ESS? (Do not just spell out the abbreviations.) [243]

An extended service set (ESS) is a group of BSSs that are connected to the same distribution system (network) and have the same SSID.

What factors influence individual throughput, given a certain level of aggregate throughput? [253]

Another consideration is that speed is highest when a user is very near an access point. As the user moves away, speed falls. The problem is that at maximum transmission speed, there must be almost perfect propagation characteristics. As a user moves away from an access point, signal strength falls, errors There are many other factors that will reduce individual throughput. For example, there are still some wireless devices that use the old 802.11b standard, which only has a rated speed of 11 Mbps. \

1) Wireless network standards operate at ________. A) the data link layer B) the internet layer C) Both A and B D) Neither A nor B

Answer: A

12) What propagation problem becomes worse as frequency increases? A) Absorptive attenuation. B) Electromagnetic interference. C) Both A and B D) Neither A nor B

Answer: A

18) To handle multiple conversations in radio transmission, you use multiple ________. A) channels B) frequencies C) service bands D) UWBs E) wires

Answer: A

2) Wireless network standards come from ________. A) OSI B) TCP/IP C) Both A and B D) Neither A nor B

Answer: A

27) If a radio transmission is easily blocked by obstacles, then you need to maintain ________. A) a clear line of sight B) spread spectrum transmission integrity C) broadband transmission D) deep transmission E) shadow zone transmission

Answer: A

29) Interference is minimized in ________. A) licensed bands B) unlicensed bands

Answer: A

30) In unlicensed bands, ________. A) you can use radios wherever you please B) you can prevent nearby businesses from setting up access points in the same channel C) Both A and B D) Neither A nor B

Answer: A

33) Which unlicensed band is defined the same way in most countries around the world? A) 2.4 GHz. B) 5 GHz. C) Both A and B D) None of the above.

Answer: A

34) Which unlicensed band provides greater propagation distance for a given level of power? A) 2.4 GHz. B) 5 GHz. C) Both A and B allow about the same propagation distance.

Answer: A

36) What happens if two nearby access points use the same channel? A) They will interfere with each other. B) They will be bonded for joint operation automatically. C) They will be bonded for joint operation automatically if they use CSMA/CA+ACK. D) They will be bonded for joint operation automatically if they use RTS/CTS.

Answer: A

37) What aspect of 802.11 standards affects interference between nearby access points? A) The number of possible nonoverlapping channels. B) The standard's minimum spacing parameter. C) RTS/CTS. D) All of the above.

Answer: A

39) Spread spectrum transmission is used in WLANs because ________. A) it is required by regulators B) it offers strong security C) Both A and B D) Neither A nor B

Answer: A

49) In 802.11 WLANs, the terms handoff and roaming mean the same thing. A) True. B) False.

Answer: A

5) Cellular telephony uses ________. A) an omnidirectional antenna B) a dish antenna C) Both A and B D) Neither A nor B

Answer: A

50) There is an access point that serves eight wireless hosts. On how many channels will these devices transmit during the course of an hour or two? A) 1. B) 2 (one in each direction). C) 7. D) 8. E) 9.

Answer: A

52) Individual throughput falls as the number of wireless hosts using an access point increases. A) True. B) False.

Answer: A

55) (From the box, "Controlling 802.11 Transmission") When a wireless NIC receives a frame correctly, it immediately sends back a reply without listening for traffic. A) True. B) False.

Answer: A

56) (From the box, "Controlling 802.11 Transmission") CSMA/CA+ACK is reliable. A) True. B) False.

Answer: A

59) (From the box, "Controlling 802.11 Transmission") CSMA/CA+ACK usually is ________. A) required B) optional

Answer: A

61) (From the box, "Controlling 802.11 Transmission") Which of the following is more efficient? A) CSMA/CA+ACK. B) RTS/CTS. C) Both are about equally efficient.

Answer: A

70) As a wireless host moves farther from a wireless access point, it is likely to transition to a slower modulation method. A) True. B) False.

Answer: A

77) Mesh networking in 802.11 is likely to use ________. A) only wireless devices B) wireless devices and the site's wired LAN C) Both A and B

Answer: A

78) Smart antennas can ________. A) direct signal strength at individual wireless hosts B) transmit multiple spatial data streams in the same channel C) Both A and B D) Neither A nor B

Answer: A

9) The signal strength at 20 meters is 90 mW the signal strength at 60 meters would be 10 mW. A) True. B) False.

Answer: A

Answer: A A) 1.

33) Which unlicensed band is defined the same way in most countries around the world? A) 2.4 GHz. B) 5 GHz. C) Both A and B D) None of the above.

Answer: A A) 2.4 GHz.

34) Which unlicensed band provides greater propagation distance for a given level of power? A) 2.4 GHz. B) 5 GHz. C) Both A and B allow about the same propagation distance.

Answer: A A) 2.4 GHz.

12) What propagation problem becomes worse as frequency increases? A) Absorptive attenuation. B) Electromagnetic interference. C) Both A and B D) Neither A nor B

Answer: A A) Absorptive attenuation.

61) (From the box, "Controlling 802.11 Transmission") Which of the following is more efficient? A) CSMA/CA+ACK. B) RTS/CTS. C) Both are about equally efficient.

Answer: A A) CSMA/CA+ACK.

2) Wireless network standards come from ________. A) OSI B) TCP/IP C) Both A and B D) Neither A nor B

Answer: A A) OSI

Answer: A A) The number of possible nonoverlapping channels.

Answer: A A) They will interfere with each other.

49) In 802.11 WLANs, the terms handoff and roaming mean the same thing. A) True. B) False.

Answer: A A) True.

52) Individual throughput falls as the number of wireless hosts using an access point increases. A) True. B) False.

Answer: A A) True.

55) (From the box, "Controlling 802.11 Transmission") When a wireless NIC receives a frame correctly, it immediately sends back a reply without listening for traffic. A) True. B) False.

Answer: A A) True.

56) (From the box, "Controlling 802.11 Transmission") CSMA/CA+ACK is reliable. A) True. B) False.

Answer: A A) True.

70) As a wireless host moves farther from a wireless access point, it is likely to transition to a slower modulation method. A) True. B) False.

Answer: A A) True.

9) The signal strength at 20 meters is 90 mW the signal strength at 60 meters would be 10 mW. A) True. B) False.

Answer: A A) True.

Answer: A A) a clear line of sight

5) Cellular telephony uses ________. A) an omnidirectional antenna B) a dish antenna C) Both A and B D) Neither A nor B

Answer: A A) an omnidirectional antenna

18) To handle multiple conversations in radio transmission, you use multiple ________. A) channels B) frequencies C) service bands D) UWBs E) wires

Answer: A A) channels

78) Smart antennas can ________. A) direct signal strength at individual wireless hosts B) transmit multiple spatial data streams in the same channel C) Both A and B D) Neither A nor B

Answer: A A) direct signal strength at individual wireless hosts

39) Spread spectrum transmission is used in WLANs because ________. A) it is required by regulators B) it offers strong security C) Both A and B D) Neither A nor B

Answer: A A) it is required by regulators

29) Interference is minimized in ________. A) licensed bands B) unlicensed bands

Answer: A A) licensed bands

77) Mesh networking in 802.11 is likely to use ________. A) only wireless devices B) wireless devices and the site's wired LAN C) Both A and B

Answer: A A) only wireless devices

59) (From the box, "Controlling 802.11 Transmission") CSMA/CA+ACK usually is ________. A) required B) optional

Answer: A A) required

1) Wireless network standards operate at ________. A) the data link layer B) the internet layer C) Both A and B D) Neither A nor B

Answer: A A) the data link layer The data link layer and the physical layer.

30) In unlicensed bands, ________. A) you can use radios wherever you please B) you can prevent nearby businesses from setting up access points in the same channel C) Both A and B D) Neither A nor B

Answer: A A) you can use radios wherever you please

17) The terms channel and service band mean roughly the same thing. A) True. B) False.

Answer: B

19) Signals usually ________. A) travel at a single frequency B) spread over a range of frequencies

Answer: B

23) To transmit data very rapidly, you would want a ________ channel. A) narrowband B) broadband C) single-frequency band D) Any of the above.

Answer: B

24) In the Shannon Equation, C is the ________. A) actual speed of transmission in a channel B) maximum possible speed of transmission in a channel C) minimum possible speed of transmission in a channel D) channel bandwidth E) signal-to-noise ratio

Answer: B

28) WLANs normally use ________. A) licensed bands B) unlicensed bands

Answer: B

3) Wireless radio transmission usually is expressed in terms of ________. A) wavelength B) frequency C) Both A and B D) Neither A nor B

Answer: B

35) The 2.4 GHz band supports ________ nonoverlapping channels. A) 1 B) 3 C) 7 D) 11 E) more than 11

Answer: B

4) Frequency is measured in terms of ________. A) nanometers B) hertz C) Both A and B D) Neither A nor B

Answer: B

40) Spread spectrum transmission is used in WLANs for ________. A) higher transmission speed B) more reliable transmission C) greater security D) All of the above.

Answer: B

41) Spread spectrum transmission is used in commercial WLANs for security reasons. A) True. B) False.

Answer: B

45) Access points take frames from wireless devices and send these frames on to devices on the wired LAN. They also do the converse. A) True. B) False.

Answer: B

46) Access points take ________ from wireless devices and send them on to devices on the wired LAN. They also do the converse. A) frames B) packets

Answer: B

47) A wireless host sends a packet to a server on the company's wired Ethernet LAN via an access point. How many frames will be involved in this one-way transmission? A) 1. B) 2. C) 3. D) 4. E) There will be one frame for each switch along the way.

Answer: B

51) An access point and a host it serves can transmit to each other simultaneously. A) True. B) False.

Answer: B

54) (From the box, "Controlling 802.11 Transmission") When a wireless NIC wishes to transmit, it listens for traffic. If there is traffic, it waits. If there is no traffic, it may transmit. A) True. B) Sometimes true. C) False.

Answer: B

57) (From the box, "Controlling 802.11 Transmission") CSMA/CA+ACK is ________. A) efficient B) inefficient

Answer: B

6) The other wireless device is far away in a known direction. You should use ________. A) an omnidirectional antenna B) a dish antenna C) Both A and B D) Neither A nor B

Answer: B

60) (From the box, "Controlling 802.11 Transmission") Which of the following is usually optional in access point operation? A) CSMA/CA+ACK. B) RTS/CTS. C) Both A and B D) Neither A nor B

Answer: B

62) The most widely used 802.11 LAN standard today is 802.11n. A) True. B) False.

Answer: B

64) The most rapidly growing 802.11 LAN standard today is 802.11g. A) True. B) False.

Answer: B

66) There is less interference in the 2.4 GHz band than in the 5 GHz band. A) True. B) False.

Answer: B

67) 802.11g has a rated speed of ________. A) 11 Mbps B) 54 Gbps C) 300 Mbps D) 1 Gbps

Answer: B

69) An 802.11g access point has an actual speed of 30 MHz. This is ________. A) the rated speed B) aggregate throughput C) channel bandwidth

Answer: B

7) Radio has more reliable transmission than UTP. A) True. B) False.

Answer: B

8) Attenuation with distance is faster with ________. A) UTP transmission B) radio transmission C) Both A and B D) Neither A nor B

Answer: B

Answer: B B) 2.

35) The 2.4 GHz band supports ________ nonoverlapping channels. A) 1 B) 3 C) 7 D) 11 E) more than 11

Answer: B B) 3

67) 802.11g has a rated speed of ________. A) 11 Mbps B) 54 Gbps C) 300 Mbps D) 1 Gbps

Answer: B B) 54 Gbps

17) The terms channel and service band mean roughly the same thing. A) True. B) False.

Answer: B B) False.

41) Spread spectrum transmission is used in commercial WLANs for security reasons. A) True. B) False.

Answer: B B) False.

45) Access points take frames from wireless devices and send these frames on to devices on the wired LAN. They also do the converse. A) True. B) False.

Answer: B B) False.

51) An access point and a host it serves can transmit to each other simultaneously. A) True. B) False.

Answer: B B) False.

62) The most widely used 802.11 LAN standard today is 802.11n. A) True. B) False.

Answer: B B) False.

64) The most rapidly growing 802.11 LAN standard today is 802.11g. A) True. B) False.

Answer: B B) False.

7) Radio has more reliable transmission than UTP. A) True. B) False.

Answer: B B) False.

66) There is less interference in the 2.4 GHz band than in the 5 GHz band. A) True. B) False.

Answer: B B) False. More interference

60) (From the box, "Controlling 802.11 Transmission") Which of the following is usually optional in access point operation? A) CSMA/CA+ACK. B) RTS/CTS. C) Both A and B D) Neither A nor B

Answer: B B) RTS/CTS.

Answer: B B) Sometimes true.

6) The other wireless device is far away in a known direction. You should use ________. A) an omnidirectional antenna B) a dish antenna C) Both A and B D) Neither A nor B

Answer: B B) a dish antenna

69) An 802.11g access point has an actual speed of 30 MHz. This is ________. A) the rated speed B) aggregate throughput C) channel bandwidth

Answer: B B) aggregate throughput

23) To transmit data very rapidly, you would want a ________ channel. A) narrowband B) broadband C) single-frequency band D) Any of the above.

Answer: B B) broadband

3) Wireless radio transmission usually is expressed in terms of ________. A) wavelength B) frequency C) Both A and B D) Neither A nor B

Answer: B B) frequency

4) Frequency is measured in terms of ________. A) nanometers B) hertz C) Both A and B D) Neither A nor B

Answer: B B) hertz

57) (From the box, "Controlling 802.11 Transmission") CSMA/CA+ACK is ________. A) efficient B) inefficient

Answer: B B) inefficient

Answer: B B) maximum possible speed of transmission in a channel

40) Spread spectrum transmission is used in WLANs for ________. A) higher transmission speed B) more reliable transmission C) greater security D) All of the above.

Answer: B B) more reliable transmission

46) Access points take ________ from wireless devices and send them on to devices on the wired LAN. They also do the converse. A) frames B) packets

Answer: B B) packets

8) Attenuation with distance is faster with ________. A) UTP transmission B) radio transmission C) Both A and B D) Neither A nor B

Answer: B B) radio transmission

19) Signals usually ________. A) travel at a single frequency B) spread over a range of frequencies

Answer: B B) spread over a range of frequencies

28) WLANs normally use ________. A) licensed bands B) unlicensed bands

Answer: B B) unlicensed bands

13) What propagation problem becomes worse as frequency increases? A) Absorptive attenuation. B) Shadow zones. C) Both A and B D) Neither A nor B

Answer: C

14) Wireless LAN standards are created by the ________ Working Group. A) 802.1 B) 802.3 C) 802.11 D) 802.3W

Answer: C

25) In the Shannon Equation, if you quadruple the bandwidth in a channel while the signal-to-noise ratio remains the same, you can transmit ________. A) Log2(1+4) times as fast B) Log2(1+1/4) times as fast C) about 4 times as fast D) about 1/4 as fast E) at the same speed, but more reliably

Answer: C

31) 802.11 standards are being developed to work in the ________ unlicensed band. A) 2.4 GHz B) 5 GHz C) Both A and B D) None of the above.

Answer: C

32) In 802.11, channel bandwidth usually is ________. A) 20 GHz B) 40 GHz C) 20 MHz D) 40 MHz

Answer: C

42) A channel has more bandwidth than is necessary given data transmission speeds requirements in ________ transmission. A) normal radio B) reliable commercial C) spread spectrum transmission D) licensed E) None of the above.

Answer: C

43) Which of the following uses OFDM? A) 802.11g. B) 802.11n. C) Both A and B D) Neither A nor B

Answer: C

44) Which form of spread spectrum transmission divides the channel into many smaller channels called subcarriers? A) DSSS. B) FHSS. C) OFDM. D) All of the above. E) None of the above.

Answer: C

48) When a host moves from one wireless access point to another in a WLAN, this is ________. A) a handoff B) roaming C) Both A and B D) Neither A nor B

Answer: C

53) (From the box, "Controlling 802.11 Transmission") Media access control governs transmission by ________. A) access points B) wireless NICs C) Both A and B D) Neither A nor B

Answer: C

65) 802.11n is designed to operate in the ________ unlicensed band. A) 2.4 GHz B) 5 GHz C) Both A and B D) Neither A nor B

Answer: C

68) 802.11n is faster than 802.11g because 802.11n ________ A) is designed to use wider channels B) can send multiple signals (spatial transmission speeds) in a single channel C) Both A and B D) Neither A nor B

Answer: C

71) Which of the following is true? A) An 802.11n host can work with an 802.11g access point. B) An 802.11g host can work with an 802.11n access point. C) Both A and B D) Neither A nor B

Answer: C

72) 802.11n will be superior to current 802.11 standards by ________. A) offering wider channels B) sending multiple spatial data streams in a single channel between wireless access points and wireless NICs C) Both A and B D) Neither A nor B

Answer: C

73) 802.11n may offer a rated speed of about ________. A) 11 Mbps B) 54 Mbps C) 300 Mbps D) 3 Gbps

Answer: C

74) MIMO increases ________. A) throughput B) propagation distance C) Both A and B D) Neither A nor B

Answer: C

75) Which of the following can offer speeds of about a gigabit per second? A) 802.11g. B) 802.11n. C) 802.11ac. D) None of the above.

Answer: C

76) 802.11ad will ________. A) operate in the 60 GHz radio band B) have short propagation distance C) Both A and B D) Neither A nor B

Answer: C

32) In 802.11, channel bandwidth usually is ________. A) 20 GHz B) 40 GHz C) 20 MHz D) 40 MHz

Answer: C C) 20 MHz

73) 802.11n may offer a rated speed of about ________. A) 11 Mbps B) 54 Mbps C) 300 Mbps D) 3 Gbps

Answer: C C) 300 Mbps

14) Wireless LAN standards are created by the ________ Working Group. A) 802.1 B) 802.3 C) 802.11 D) 802.3W

Answer: C C) 802.11

75) Which of the following can offer speeds of about a gigabit per second? A) 802.11g. B) 802.11n. C) 802.11ac. D) None of the above.

Answer: C C) 802.11ac.

13) What propagation problem becomes worse as frequency increases? A) Absorptive attenuation. B) Shadow zones. C) Both A and B D) Neither A nor B

Answer: C C) Both A and B

31) 802.11 standards are being developed to work in the ________ unlicensed band. A) 2.4 GHz B) 5 GHz C) Both A and B D) None of the above.

Answer: C C) Both A and B

43) Which of the following uses OFDM? A) 802.11g. B) 802.11n. C) Both A and B D) Neither A nor B

Answer: C C) Both A and B

48) When a host moves from one wireless access point to another in a WLAN, this is ________. A) a handoff B) roaming C) Both A and B D) Neither A nor B

Answer: C C) Both A and B

53) (From the box, "Controlling 802.11 Transmission") Media access control governs transmission by ________. A) access points B) wireless NICs C) Both A and B D) Neither A nor B

Answer: C C) Both A and B

65) 802.11n is designed to operate in the ________ unlicensed band. A) 2.4 GHz B) 5 GHz C) Both A and B D) Neither A nor B

Answer: C C) Both A and B

71) Which of the following is true? A) An 802.11n host can work with an 802.11g access point. B) An 802.11g host can work with an 802.11n access point. C) Both A and B D) Neither A nor B

Answer: C C) Both A and B

74) MIMO increases ________. A) throughput B) propagation distance C) Both A and B D) Neither A nor B

Answer: C C) Both A and B

76) 802.11ad will ________. A) operate in the 60 GHz radio band B) have short propagation distance C) Both A and B D) Neither A nor B

Answer: C C) Both A and B

44) Which form of spread spectrum transmission divides the channel into many smaller channels called subcarriers? A) DSSS. B) FHSS. C) OFDM. D) All of the above. E) None of the above.

Answer: C C) OFDM.

Answer: C C) about 4 times as fast

Answer: C C) spread spectrum transmission

10) The most serious problem with wireless transmission in WLANs is ________. A) inverse square law attenuation B) absorptive attenuation C) shadow zones D) multipath interference

Answer: D

11) What propagation problem becomes worse as frequency increases? A) Inverse square law attenuation. B) Electromagnetic interference. C) Both A and B D) Neither A nor B

Answer: D

16) The total range of possible 802.11 WLAN frequencies in the 2.4 GHz band constitutes ________. A) a frequency spectrum B) a broadband C) a channel D) a service band E) All of the above.

Answer: D

20) A channel extends from 55 MHz to 60 MHz. Its bandwidth is ________. A) 60 MHz B) 55 MHz C) 65 MHz D) None of the above.

Answer: D

21) To transmit very rapidly in RADIO, you need ________. A) single-frequency transmission B) single-mode transmission C) multimode transmission D) wide bandwidth E) narrow bandwidth

Answer: D

22) Channels with wide bandwidths are called ________ channels. A) single-mode B) multimode C) full-duplex D) broadband E) modulated

Answer: D

26) The frequency range from 500 megahertz to 10 gigahertz is called the ________. A) frequency spectrum B) commercial mobile service band C) UWB region D) golden zone E) unlicensed band

Answer: D

38) 802.11a supports ________ nonoverlapping channels. A) 1 B) 3 C) 7 D) More than 10

Answer: D

58) (From the box, "Controlling 802.11 Transmission") In ________, when a wireless host wishes to send, it first sends a message to the wireless access point asking for permission to send. When the access point sends back a response, the host sending the original message may transmit. All other hosts must wait. A) CSMA/CA+ACK B) CSMA/CA C) CSMA/CD D) RTS/CTS

Answer: D

63) The most widely used 802.11 standard today is ________. A) 802.11a B) 802.11b C) 802.11e D) 802.11g E) 802.11n

Answer: D

63) The most widely used 802.11 standard today is ________. A) 802.11a B) 802.11b C) 802.11e D) 802.11g E) 802.11n

Answer: D D) 802.11g

38) 802.11a supports ________ nonoverlapping channels. A) 1 B) 3 C) 7 D) More than 10

Answer: D D) More than 10

11) What propagation problem becomes worse as frequency increases? A) Inverse square law attenuation. B) Electromagnetic interference. C) Both A and B D) Neither A nor B

Answer: D D) Neither A nor B

20) A channel extends from 55 MHz to 60 MHz. Its bandwidth is ________. A) 60 MHz B) 55 MHz C) 65 MHz D) None of the above.

Answer: D D) None of the above.

Answer: D D) RTS/CTS

16) The total range of possible 802.11 WLAN frequencies in the 2.4 GHz band constitutes ________. A) a frequency spectrum B) a broadband C) a channel D) a service band E) All of the above.

Answer: D D) a service band

22) Channels with wide bandwidths are called ________ channels. A) single-mode B) multimode C) full-duplex D) broadband E) modulated

Answer: D D) broadband

26) The frequency range from 500 megahertz to 10 gigahertz is called the ________. A) frequency spectrum B) commercial mobile service band C) UWB region D) golden zone E) unlicensed band

Answer: D D) golden zone

10) The most serious problem with wireless transmission in WLANs is ________. A) inverse square law attenuation B) absorptive attenuation C) shadow zones D) multipath interference

Answer: D D) multipath interference

21) To transmit very rapidly in RADIO, you need ________. A) single-frequency transmission B) single-mode transmission C) multimode transmission D) wide bandwidth E) narrow bandwidth

Answer: D D) wide bandwidth

15) The frequency spectrum extends ________. A) into the megahertz range B) into the gigahertz range C) into the visible light range D) into the ultraviolet range E) to infinity

Answer: E

15) The frequency spectrum extends ________. A) into the megahertz range B) into the gigahertz range C) into the visible light range D) into the ultraviolet range E) to infinity

Answer: E E) to infinity

What is the advantage of using unlicensed bands? [235]

Any wireless host can be turned on or moved around without the need for any government approval.

Given their relative bandwidths, about how many times as much data is sent per second in television than in AM radio? (The information to answer this question is in the text.) [231].

Approximately 600 times more data are sent per second in television as opposed to AM radio.

Why does transmission speed drop as a computer moves farther from an access point? [253]

As distance increase, attenuation increases therefore the wireless access point have to switch to a more reliable frequency which results in slower speeds.

Which attenuates more rapidly with distance—signals sent through wired media or radio signals?

Attenuation with radio signal rapidly increases as distance increases

1) Wireless network standards operate at ________. A) the internet layer B) the data link layer C) Both A and B D) Neither A nor B

10) Attenuation with distance is faster with ________. A) UTP transmission B) radio transmission C) Both A and B D) Neither A nor B

12) The most serious problem with wireless transmission in WLANs is ________. A) inverse square law attenuation B) multipath interference C) shadow zones D) absorptive attenuation

14) What propagation problem becomes worse as frequency increases? A) Electromagnetic interference. B) Absorptive attenuation. C) Both A and B D) Neither A nor B

20) Signals usually ________. A) travel at a single frequency B) spread over a range of frequencies

24) To transmit data very rapidly, you would want a ________ channel. A) narrowband B) broadband C) single-frequency band D) Any of the above

26) In the Shannon Equation, C is the ________. A) actual speed of transmission in a channel B) maximum possible speed of transmission in a channel C) minimum possible speed of transmission in a channel D) channel bandwidth

30) WLANs normally use ________. A) licensed bands B) unlicensed bands

36) Which unlicensed band provides greater propagation distance for a given level of power? A) 5 GHz. B) 2.4 GHz. C) Both A and B allow about the same propagation distance.

37) The 2.4 GHz band supports ________ nonoverlapping 20 MHz channel(s). A) 7 B) 3 C) 11 D) 1

37) The 2.4 GHz band supports ________ nonoverlapping 20 MHz channel(s). A) 1 B) 3 C) 7 D) 11

38) The 5 GHz band supports about ________ nonoverlapping 20 MHz channel(s). A) 3 B) 12 C) 6 D) 1

4) Wireless access points typically link wireless clients to ________. A) wireless servers B) servers on the wired network C) Both A and B

40) Spread spectrum transmission is used in WLANs for ________. A) greater security B) more reliable transmission C) higher transmission speed D) All of the above

40) Spread spectrum transmission is used in WLANs for ________. A) higher transmission speed B) more reliable transmission C) greater security D) All of the above

41) Spread spectrum transmission is used in commercial WLANs for security reasons.

44) When a WLAN is in use, the distribution system is the ________. A) radio transmitter in an access point B) Ethernet network C) radio transmitter in the access point controller D) collection of access points

44) When a WLAN is in use, the distribution system is the ________. A) collection of access points B) Ethernet network C) radio transmitter in an access point D) radio transmitter in the access point controller

47) A wireless host sends a packet to a server on the company's wired Ethernet LAN via an access point. How many frames will be involved in this one-way transmission? A) 1 B) 2 C) 4 D) There will be one frame for each switch along the way.

49) The ________ is the identifier in a basic service set. A) BSS B) BSSID C) SSID

5) Wireless radio transmission usually is expressed in terms of ________. A) wavelength B) frequency C) Both A and B D) Neither A nor B

54) In an extended service set, each access point ________. A) must have coordinated SSIDs B) must have the same SSID C) must have different SSIDs D) None of the above

56) What happens if two nearby access points use the same channel? A) They will be bonded for joint operation automatically. B) They will interfere with each other. C) They will be bonded for joint operation automatically if they use CSMA/CA+ACK. D) They will be bonded for joint operation automatically if they use RTS/CTS.

6) Frequency is measured in terms of ________. A) nanometers B) hertz C) Both A and B D) Neither A nor B

61) When a wireless NIC wishes to transmit, it listens for traffic. If there is traffic, it waits. If there is no traffic, it may transmit. A) True. B) Sometimes true. C) False.

64) CSMA/CA+ACK is ________. A) efficient B) inefficient

66) CSMA/CA+ACK usually is ________. A) optional B) required

67) Which of the following is usually optional in access point operation? A) CSMA/CA+ACK. B) RTS/CTS. C) Both A and B D) Neither A nor B

7) The other wireless device is far away in a known direction. You should use ________. A) an omnidirectional antenna B) a dish antenna C) Both A and B D) Neither A nor B

72) For which of the following is 100 meters a typical service distance? A) 802.11g. B) 802.11n. C) Both A and B D) Neither A nor B

73) Which of the following brings gigabit speeds to clients? A) 802.11n B) 802.11ac C) 802.11g D) None of the above

78) In the 5 GHz band, how many channels can you have with 802.11ac with 80 GHz channels? A) 1 B) 6 C) 12 D) 24

79) In the 60 GHz service band, ________. A) signals travel farther B) channel bandwidth can be very wide C) Both A and B D) Neither A nor B

85) Traditional MIMO can ________ A) send signals to two different clients at the same time B) send multiple signals in the same channel C) Both A and B D) Neither A nor B

87) In 802.11 networks, the speed I receive on my portable devices is a(n) ________. A) aggregate throughput B) individual throughput C) rated speed D) None of the above

91) If an 802.11n access point and an 802.11g client communicate, they communicate using ________. A) 802.11n B) 802.11g C) Either A or B D) Neither A nor B

Which of the following brings gigabit speeds to clients? A) 802.11n B) 802.11ac C) 802.11g D) None of the above

B) 802.11ac

91) If an 802.11n access point and an 802.11g client communicate, they communicate using ________. A) 802.11n B) 802.11g C) Either A or B D) Neither A nor B

B) 802.11g

Traditional MIMO can ________ A) send signals to two different clients at the same time B) send multiple signals in the same channel C) Both A and B D) Neither A nor B

B) send multiple signals in the same channel

A single access point and the set of hosts it serves is called a(n) ________.

BSS

What is a BSS? (Do not just spell out the acronym.) [242]

Basic service set (BSS) A basic service set (BSS) consists of an access point and the set of hosts it serves

To transmit data very rapidly, you would want a ________ channel.

Broadband

OFDM Describe it. [240]

Broadband channels are dived into smaller sub channels called carriers. Parts of each frame are transmitted in each subcarrier. OFDM sends data redundantly across the subcarriers, so if there is impairment in one or even a few subcarriers, all of the data usually will get through.

How does MIMO work? [251]

By having the host or access point send two or more spatial streams (radio signals) in the same channel between tow or more different antennas on access point and wireless hosts.

15) What propagation problem becomes worse as frequency increases? A) Shadow zones. B) Absorptive attenuation. C) Both A and B D) Neither A nor B

15) What propagation problem becomes worse as frequency increases? A) Absorptive attenuation. B) Shadow zones. C) Both A and B D) Neither A nor B

17) The total range of possible 802.11 WLAN frequencies in the 2.4 GHz band constitutes ________. A) a frequency spectrum B) a broadband C) a service band D) a channel

19) To handle multiple conversations in radio transmission, you use multiple ________. A) service bands B) frequencies C) channels D) wires

22) To transmit very rapidly in RADIO, you need ________. A) single-frequency transmission B) single-mode transmission C) wide bandwidth D) narrow bandwidth

23) Channels with wide bandwidths are called ________ channels. A) multimode B) full-duplex C) broadband D) modulated

24) To transmit data very rapidly, you would want a ________ channel. A) single-frequency band B) narrowband C) broadband D) Any of the above

26) In the Shannon Equation, C is the ________. A) actual speed of transmission in a channel B) minimum possible speed of transmission in a channel C) maximum possible speed of transmission in a channel D) channel bandwidth

27) In the Shannon Equation, if you quadruple the bandwidth in a channel while the signal-to-noise ratio remains the same, you can transmit ________. A) Log2(1+4) times as fast B) Log2(1+1/4) times as fast C) about 4 times as fast D) at the same speed, but more reliably

28) The frequency range from 500 megahertz to 10 gigahertz is called the ________. A) frequency spectrum B) unlicensed band C) golden zone D) commercial mobile service band

3) Wireless LAN standards are created by the ________ Working Group. A) 802.1 B) 802.3 C) 802.11 D) 802.3W

33) 802.11 standards are being developed to work in the ________ unlicensed band. A) 5 GHz B) 2.4 GHz C) Both A and B D) Neither A nor B

33) 802.11 standards are being developed to work in the ________ unlicensed band. A) 2.4 GHz B) 5 GHz C) Both A and B D) Neither A nor B

34) In 802.11, channel bandwidth usually is ________. A) 20 GHz B) 40 GHz C) 20 MHz D) 40 MHz

42) A channel has more bandwidth than is necessary given data transmission speeds requirements in ________ transmission. A) normal radio B) reliable commercial C) spread spectrum D) licensed

43) Which of the following uses OFDM? A) 802.11n. B) 802.11g. C) Both A and B D) Neither A nor B

43) Which of the following uses OFDM? A) 802.11g. B) 802.11n. C) Both A and B D) Neither A nor B

48) An access point and the set of hosts it serves is called a(n) ________. A) BSSID B) ESS C) BSS D) None of the above

49) The ________ is the identifier in a basic service set. A) BSSID B) BSS C) SSID

51) When a host moves from one wireless access point to another in a WLAN, this is ________. A) roaming B) a handoff C) Both A and B D) Neither A nor B

51) When a host moves from one wireless access point to another in a WLAN, this is ________. A) a handoff B) roaming C) Both A and B D) Neither A nor B

53) An extended service set (ESS) is a group of BSSs that ________. A) have the same SSID B) are connected to the same distribution system C) Both A and B D) Neither A nor B

53) An extended service set (ESS) is a group of BSSs that ________. A) are connected to the same distribution system B) have the same SSID C) Both A and B D) Neither A nor B

55) The standard for roaming among access points is ________. A) 802.11s B) 802.11W C) 802.11r D) None of the above

57) There is an access point that serves eight wireless hosts. On how many channels will these devices transmit during the course of an hour or two? A) 7 B) 8 C) 1 D) 2

58) ________ is a technique for preventing two wireless stations from transmitting at the same time and therefore interfering with each other. A) Roaming B) The distribution system C) Media access control D) Creating extended service sets

60) Media access control governs transmission by ________. A) access points B) wireless hosts C) Both A and B D) Neither A nor B

65) In ________, when a wireless host wishes to send, it first sends a message to the wireless access point asking for permission to send. When the access point sends back a response, the host sending the original message may transmit. All other hosts must wait. A) CSMA/CA B) CSMA/CA+ACK C) RTS/CTS D) CSMA/CD

71) For which standard is 300 Mbps a typical rated speed? A) 802.11ad. B) 802.11ac. C) 802.11n. D) 802.11g.

74) For wireless backup, which of the following is adequate? A) 802.11g B) 802.11n C) 802.11ac D) All of the above

75) Which of the following uses OFDM? A) 802.11ac B) 802.11g C) Both A and B D) Neither A nor B

78) In the 5 GHz band, how many channels can you have with 802.11ac with 80 GHz channels? A) 1 B) 12 C) 6 D) 24

80) MIMO ________. A) uses a single spatial stream but multiple signals B) bonds channels for higher speed C) transmits multiple signals in the same channel D) is used in all forms of 802.11

83) Beamforming can ________. A) direct signal strength at individual wireless hosts B) transmit multiple spatial data streams in the same channel C) Both A and B D) Neither A nor B

84) Beamforming can allow an access point to ________. A) send signals to two different clients at the same time B) direct power to individual clients C) Both A and B D) Neither A nor B

84) Beamforming can allow an access point to ________. A) direct power to individual clients B) send signals to two different clients at the same time C) Both A and B D) Neither A nor B

87) In 802.11 networks, the speed I receive on my portable devices is a(n) ________. A) individual throughput B) rated speed C) aggregate throughput D) None of the above

92) Using unused transmission channels in a service band is called using ________. A) dark spectrum B) opportunistic agility C) white space D) a smart antenna

Write the Shannon Equation. List what each letter is in the equation. [231]

C = B [Log^2 (1+S/N)] C = Maximum possible transmission speed in the channel (bps) B = Bandwidth (Hz) S/N = Signal-to-noise ratio measured as the power ratio, not as decibels Note that doubling the bandwidth doubles the maximum possible transmission speed Multiplying the bandwidth by X multiplies the maximum possible speed by X Wide bandwidth is the key to fast transmission Increasing S/N helps slightly, but usually cannot be done to any significant extent

78) In the 5 GHz band, how many channels can you have with 802.11ac with 80 GHz channels? A) 1 B) 12 C) 6 D) 24

C) 6

For wireless backup, which of the following is adequate? A) 802.11g B) 802.11n C) 802.11ac D) All of the above

C) 802.11ac

71) For which standard is 300 Mbps a typical rated speed? A) 802.11ad. B) 802.11ac. C) 802.11n. D) 802.11g.

C) 802.11n.

83) Beamforming can ________. A) direct signal strength at individual wireless hosts B) transmit multiple spatial data streams in the same channel C) Both A and B D) Neither A nor B

C) Both A and B

Beamforming can allow an access point to ________. A) send signals to two different clients at the same time B) direct power to individual clients C) Both A and B D) Neither A nor B

C) Both A and B

87) In 802.11 networks, the speed I receive on my portable devices is a(n) ________. A) individual throughput B) rated speed C) aggregate throughput D) None of the above

C) aggregate throughput

MIMO ________. A) uses a single spatial stream but multiple signals B) bonds channels for higher speed C) transmits multiple signals in the same channel D) is used in all forms of 802.11

C) transmits multiple signals in the same channel

Using unused transmission channels in a service band is called using ________. A) dark spectrum B) opportunistic agility C) white space D) a smart antenna

C) white space

The 802.11 standard has two mechanisms for media access control. One of two mechanisms is mandatory; it is ________.

CSMA/CA+ACK

What is a collision? [244] Why is it bad? [244]

Channel Sharing The access point and all the hosts it serves transmit in a single channel. If two devices transmit at the same time, their signals will collide, becoming unreadable. (If two devices transmit in the same channel at the same time, their signals will interfere with each other.)

To handle multiple conversations in radio transmission, you normally use multiple ________.

Channels

What feature do all access points in an ESS share? [243]

Connected to the same distribution system (network) and have the same SSID.

List some sources of EMI[229]

Cordless telephones, microwaves and devices near the wireless network

12) The most serious problem with wireless transmission in WLANs is ________. A) inverse square law attenuation B) absorptive attenuation C) shadow zones D) multipath interference

13) What propagation problem becomes worse as frequency increases? A) Inverse square law attenuation. B) Electromagnetic interference. C) Both A and B D) Neither A nor B

16) The frequency spectrum extends ________. A) into the ultraviolet range B) into the gigahertz range C) into the visible light range D) to infinity

16) The frequency spectrum extends ________. A) into the gigahertz range B) into the visible light range C) into the ultraviolet range D) to infinity

17) The total range of possible 802.11 WLAN frequencies in the 2.4 GHz band constitutes ________. A) a frequency spectrum B) a broadband C) a channel D) a service band

21) A channel extends from 55 MHz to 60 MHz. Its bandwidth is ________. A) 65 MHz B) 60 MHz C) 55 MHz D) None of the above

21) A channel extends from 55 MHz to 60 MHz. Its bandwidth is ________. A) 60 MHz B) 55 MHz C) 65 MHz D) None of the above

28) The frequency range from 500 megahertz to 10 gigahertz is called the ________. A) frequency spectrum B) commercial mobile service band C) unlicensed band D) golden zone

29) If a radio transmission is easily blocked by obstacles, then you need to maintain ________. A) deep transmission B) broadband transmission C) spread spectrum transmission interference D) a clear line of sight

38) The 5 GHz band supports about ________ nonoverlapping 20 MHz channel(s). A) 1 B) 3 C) 6 D) 12

42) A channel has more bandwidth than is necessary given data transmission speeds requirements in ________ transmission. A) licensed B) reliable commercial C) normal radio D) spread spectrum

50) To connect to an access point, you must know its ________. A) DSS B) BSS C) ESS D) None of the above

50) To connect to an access point, you must know its ________. A) BSS B) DSS C) ESS D) None of the above

58) ________ is a technique for preventing two wireless stations from transmitting at the same time and therefore interfering with each other. A) Creating extended service sets B) Roaming C) The distribution system D) Media access control

69) Which of the following is a full, according to the book? A) 802.11ac. B) 802.11ad. C) Both A and B D) Neither A nor B

70) Which of the following is a draft standard, according to the book? A) 802.11n. B) 802.11g. C) Both A and B D) Neither A nor B

70) Which of the following is a draft standard, according to the book? A) 802.11g. B) 802.11n. C) Both A and B D) Neither A nor B

71) For which standard is 300 Mbps a typical rated speed? A) 802.11ac. B) 802.11ad. C) 802.11g. D) 802.11n.

72) For which of the following is 100 meters a typical service distance? A) 802.11n. B) 802.11g. C) Both A and B D) Neither A nor B

76) Wider channel bandwidth ________. A) allows more channels to be used in a service band B) decreases transmission speed C) Both A and B D) Neither A nor B

80) MIMO ________. A) bonds channels for higher speed B) is used in all forms of 802.11 C) uses a single spatial stream but multiple signals D) transmits multiple signals in the same channel

92) Using unused transmission channels in a service band is called using ________. A) dark spectrum B) a smart antenna C) opportunistic agility D) white space

93) Two wireless devices communicate via Wi-Fi Direct using ________. A) an access point that lets them talk directly B) an Ethernet network to connect their access points C) Either A or B D) Neither A nor B

95) The 802.11 standard for mesh networking is ________. A) 802.11r B) 802.11m C) 802.11ac D) None of the above

70) Which of the following is a draft standard, according to the book? A) 802.11n. B) 802.11g. C) Both A and B D) Neither A nor B

D) Neither A nor B

72) For which of the following is 100 meters a typical service distance? A) 802.11n. B) 802.11g. C) Both A and B D) Neither A nor B

D) Neither A nor B

76) Wider channel bandwidth ________. A) allows more channels to be used in a service band B) decreases transmission speed C) Both A and B D) Neither A nor B

D) Neither A nor B

Which of the following is a full, according to the book? A) 802.11ac. B) 802.11ad. C) Both A and B D) Neither A nor B

D) Neither A nor B

95) The 802.11 standard for mesh networking is ________. A) 802.11r B) 802.11m C) 802.11ac D) None of the above

D) None of the above

What business application will gigabit transmission speed make feasible to do wirelessly?

Data backup, sharing data, and syncing data

How can access points communicate with each other? [243]

Distribution system.

11) If the signal strength at 20 meters is 90 mW, the signal strength at 60 meters would be 10 mW.

FALSE

18) The terms channel and service band mean roughly the same thing.

FALSE

41) Spread spectrum transmission is used in commercial WLANs for security reasons.

FALSE

45) Access points take frames from wireless devices and send these frames on to devices on the wired LAN.

FALSE

59) An access point and a host it serves can transmit to each other simultaneously.

FALSE

9) Radio has more reliable transmission than UTP.

FALSE

96) Two WLAN products that conform to the same standard will have almost equal performance.

FALSE

18) The terms channel and service band mean roughly the same thing.

False

25) Networks that are fast are often called broadband whether or not they use radio channels.

False

45) Access points take frames from wireless devices and send these frames on to devices on the wired LAN.

False

59) An access point and a host it serves can transmit to each other simultaneously.

False

62) When a wireless NIC using CSMA/CD receives a frame correctly, it immediately sends back a reply without listening for traffic.

False

9) Radio has more reliable transmission than UTP.

False

96) Two WLAN products that conform to the same standard will have almost equal performance.

False

Two WLAN products that conform to the same standard will have almost equal performance. (True or False)

False Will not have equal performance.

Is wireless radio transmission usually expressed in terms of wavelength or frequency? [226]

Frequency

Distinguish among the frequency spectrum, service bands, and channels. [230]

Frequency spectrum all possible frequencies from zero hertz to infinity. Service bands contiguous spectrum ranges within a frequency spectrum. Channels are subdivided service brands with smaller frequency ranges

Beamforming What two benefits can it bring? [252]

Gives more effective power, stronger signal to each wireless host and greater propagation distance.

Why is the golden zone important? [234]

Golden zone frequencies are high enough for there to be large total bandwidth At higher frequencies, there is more available bandwidth Golden zone frequencies are low enough to allow fairly good propagation characteristics At lower frequencies, signals propagate better

What is the main benefit of MIMO? What is its other benefit? [251]

Greater transmission speed & greater transmission distance.

How does the presence of a distant station harm all users of an access point? [253]

Hosts connected with an access point are some that are farther away, throughput will fall because signal have to travel longer distance and will take longer to send and receive packets, and this time will be take away from other users.

802.11s standard Panko, Raymond; Panko, Julia (2012-10-09). Business Data Networks and Security (9th Edition) (Page 256). Prentice Hall. Kindle Edition.

How does Wi-Fi Direct differ from the traditional way in which two wireless hosts communicate?[255] Adhoc connection, no access point need and its simpler. b) Can a large Wi-Fi network operate without an Ethernet switched backbone? [256] yes c) What technology allows this? [256] adhoc d) What is the current 802.11 standard for this technology? [256]

Why is the number of non-overlapping channels that can be used important? [235-237]

If nearby access points operate in the same channel, their signals will interfere with each other unless the access points are far apart. This interference is called co-channel interference.

Does media access control limit the actions of wireless hosts, the access point, or both? [244]

MAC limits both the actions of wireless hosts and the access point.

What happens to the maximum possible propagation speed in a channel if the bandwidth is tripled while the signal-to-noise ratio remains the same? [231]

Maximum possible transmission is trippled

What information does C give you? [231]

Maximum possible transmission speed in the channel (bps)

What is the purpose of media access control? [244]

Media access control (MAC) methods govern when hosts and access points may transmit so that collisions can be avoided. The access point and all of the wireless hosts it serves transmit and receive in a single channel. When a host or the access point transmits, all other devices must wait.

What spread spectrum transmission method is used for the most recent 802.11 standards? [240]

Most recent 802.11 standards use Orthogonal Frequency Division Multiplexing (OFDM)

What is the most serious propagation problem in WLANs? [229]

Multipath interference may cause the signal to range from strong to nonexistent within a few centimeters

Distinguish between MIMO and multiuser MIMO. [252]

Multiuser MIMO is the possibility of simultaneously transmission in a single channel by multiple devices that are using a single access point as oppose to just one on MIMO. Beamforming can also bring multiuser MIMO, which is the possibility of simultaneous transmission in a single channel by multiple devices that are using a single access point. The 802.11n standard specified multiuser MIMO, but it did not specify a single multiuser MIMO technology. This led to a great deal of market confusion, and multiuser MIMO did not become popular with 802.11n. With 802.11ac, the Technical Group 802.11ac avoided market confusion by specifying a single multiuser MIMO technique. Beamforming is likely to be common in 802.11ac products.

A channel extends from 55 MHz to 60 MHz. Its bandwidth is ________.

None of these

In normal radio operation, how does channel bandwidth usually relate to the bandwidth required to transmit a data stream of a given speed? [239]

Normal Transmission versus Spread Spectrum Transmission (See Figure 6-16) Normal transmission uses only the channel bandwidth required by your signaling speed Spread spectrum transmission uses channels much wider than signaling speed requires

What spread spectrum method do all four standards use as their main method?

OFDM

Wireless network standards are ________ standards.

OSI

When a device designed to use a newer standard must work with a device that only uses an older standard, what standard do they use to communicate? [254]

Older standard

What type of antenna normally is used in WLANs? Why? [227]

Omnidirectional antennas are normally used in WLANs, because transmission of signal is equally strong in all direction, transmission signal spread in all three dimensions and receives incoming signal well from all direction. They are best for short distance.

Distinguish between omnidirectional and dish antennas in terms of operation. [227]

Omnidirectional can transmit three-dimensional signal transmission but short distance while dish antennas can point transmission of signals in one direction. Signals can also travel longer distances because of focusability.

What is a hertz? [226]

One cycle per second

At what layers do wireless networks operate? [224]

Physical Link and Data Link Layers.

Distinguish between rated speed, aggregate throughput, and individual throughput. [253]

RATED SPEED VERSUS THROUGHPUT Rated speed is the number of bits that the host or access point will transmit per second. access point throughput is aggregate throughput, which is shared by all users of an access point. Suppose that the aggregate throughput is 100 Mbps per second and there are 10 users of an access point. then individual throughput would be about 10 Mbps (actually somewhat less because of time lost in turn-taking). Of course, it would be rare for all stations to transmit simultaneously. However, even if three are sending and receiving simultaneously, the individual throughput they experience would be about 30 Mbps. Access point throughput is aggregate throughput This must be shared by all stations currently sending or receiving Individual throughput can be much lower than aggregate throughput

Why is multipath interference very sensitive to location? [229]

Radio waves tend to bounce off walls, floors, and other object therefore direct signal and out of bounced signal may arrive out of phase when they arrive to the receiver because they travel different distances. The signals then cancels out.

CSMA/CD+ACK is ________.

Reliable

To connect to an access point, you must know its ________.

SSID

What three issues must be overcome to make mesh networking acceptable to corporations? [256]

Self-organizing, overloading near the geographical center of the mesh, and securities

In radio, how can you send multiple signals without the signals interfering with one another? [230]

Service bands are subdivided into smaller frequency ranges called channels. A different signal can be sent in each channel because signals in different channels do not interfere with one another. This is why you can receive different television channels successfully.

What propagation problems become worse as frequency increases? [230]

Shadow zone propagation problems tend to grow worse with frequency

Under what circumstances would you use an omnidirectional antenna? [227]

Short distances, three dimensional signal transmissions.

) If spectrum scarcity becomes a problem, how will that affect users? [255]

Slower growth and cost for transmission will rise

Why must wireless devices know the access point's SSID? [243]

So wireless devices knows how to associate the access point.

Why may spectrum scarcity be a problem?

Spectrum scarcity may be a problem because unless more efficient wireless transmission methods emerge very rapidly, spectrum capacity will place limits on demand growth.

Compare the range of rated speeds possible 802.11g with 40 MHz channels and 802.11ac. [251]

Speeds for 802.11 with 40 MHz channels is 300 Mbps. 802.11ac doubles the possible spatial streams to eight. This creates a large number of possible rated speeds of 433 Mbps, 867 Mbps and 1.3 Gbps.

Does a signal usually travel at a single frequency, or does it spread over a range of frequencies? [231]

Spread over a range of frequencies called bandwidth.

Is spread spectrum transmission done for security reasons in commercial WLANs? [239]

Spread spectrum transmission is not done for security reasons in commercial WLANs.

What is the benefit of spread spectrum transmission for business communication? [238]

Spread spectrum transmission is transmission that uses far wider channels than transmission speed requires therefore reducing propagation problems and channel interference.

How does this change in spread spectrum transmission? [239]

Spread spectrum transmission is transmission that uses far wider channels than transmission speed requires.

25) Networks that are fast are often called broadband whether or not they use radio channels.

TRUE

52) In 802.11 WLANs, the terms handoff and roaming mean the same thing.

TRUE

62) When a wireless NIC using CSMA/CD receives a frame correctly, it immediately sends back a reply without listening for traffic.

TRUE

63) CSMA/CA+ACK is reliable.

TRUE

81) MIMO allows you to transmit two signals in the same channel.

TRUE

86) Another name for beamforming is having a smart antenna.

TRUE

89) As a station moves away from an access point, the access point transmits more slowly to it.

TRUE

90) The presence of a client that is distant from the access point reduces the individual throughput of other clients served by that access point.

TRUE

97) If a wireless client only has two MIMO antennas, an access point with three MIMO antennas will produce better performance than an access point with two MIMO antennas.

TRUE

What is white space, and why is using it attractive? [255]

The FCC is now considering how equipment can use empty channels (known as white space) on an opportunistic basis. This can provide more spectrum capacity for WLAN operation, cellular and similar service, or both. Regulatory agencies around the world are now considering how to allocate white space. Panko, Raymond; Panko, Julia (2012-10-09). Business Data Networks and Security (9th Edition) (Page 255). Prentice Hall. Kindle Edition.

What is the relationship between handoffs and roaming in WLANs? [243]

The ability to use handoff ins is called roaming in WLANs

Does the access point have an SSID? [243]

The access point in a BSS has an identifier called the service set identifier (SSID). Wireless hosts must know the SSID to associate with the access point.

What is the golden zone in commercial mobile radio transmission? [234]

The golden zone for commercial mobile services is 500 MHz to 10 GHz.

Why is large channel bandwidth desirable? [231]

The maximum possible speed is directly proportional to bandwidth, so if you double the bandwidth, you can potentially transmit up to twice as fast.

In the figure, what is the distribution system? [241]

The network to which access point connect (Wired Ethernet LAN).

Why can two products that comply with the same standard have different performance? [257]

The number of hardware varies between manufacturer such as number of antenna and processor used.

Does the 2.4 GHz band or the 5 GHz band allow longer propagation distances for a given level of power? Justify your answer. [235-237]

The power required for 2.4 Ghz band is lower allowing it to transmit longer distances however, 5 Ghz bands use higher frequencies therefore higher absorptive attenuation.

What is the downside of wider channel bandwidth? [250]

The wider channel bandwidth the fewer channels.

What happens if two nearby access points use the same channel?

They will interfere with each other.

What other types of system do we call broadband? [233]

Transmission systems that are very fast are usually called broadband systems even when they do not use channels.

What other types of system do we call broadband? [233]

Transmission systems: They are very fast are usually called broadband systems even when they do not use channels.

What is the advantage of having three antennas rather than two on an access point? [257]

Transmit three spatial streams allowing for a faster data transfer and better reliability.

11) If the signal strength at 20 meters is 90 mW, the signal strength at 60 meters would be 10 mW.

True

52) In 802.11 WLANs, the terms handoff and roaming mean the same thing.

True

63) CSMA/CA+ACK is reliable.

True

81) MIMO allows you to transmit two signals in the same channel.

True

86) Another name for beamforming is having a smart antenna.

True

89) As a station moves away from an access point, the access point transmits more slowly to it.

True

90) The presence of a client that is distant from the access point reduces the individual throughput of other clients served by that access point.

True

97) If a wireless client only has two MIMO antennas, an access point with three MIMO antennas will produce better performance than an access point with two MIMO antennas.

True

If a wireless client only has two MIMO antennas, an access point with three MIMO antennas will produce better performance than an access point with two MIMO antennas. (True or False)

True

The presence of a client that is distant from the access point reduces the individual throughput of other clients served by that access point. (True or False)

True

81) MIMO allows you to transmit two signals in the same channel. (True or False)

True.

86) Another name for beamforming is having a smart antenna. (True or False)

True.

As a station moves away from an access point, the access point transmits more slowly to it.(True or False)

True.

What is the disadvantage? [235]

Users must be able to tolerate interference from others

Do WLANs today use licensed or unlicensed bands? [235]

WLANs use unlicensed bands

Which offers more reliable transmission characteristics—UTP or radio transmission? [228]

What are the benefits and problems of transmission in the 60 GHz band? [250]

Winder channels but less channels available to use

Why is a wired LAN usually still needed if you have a wireless LAN? [241]

Wireless LANs is typically used to connect a small number of mobile devices to a large wired LAN typically Ethernet LAN because the servers and Internet access routers that mobile hosts need to use usually are on the wired LAN

Why do wireless clients need access to the wired Ethernet LAN? [225]

Wireless clients to access network resources it needs to be connect to wireless access point, which is usually connected to Ethernet LAN where resources such as Internet access router are usually located. 802.11 WLANs today are also primarily supplement wired LANs.

Are wireless network standards OSI standards or TCP/IP standards? Explain. [224]

Wireless network are also single network, which require physical and data link layer standards so they are also OSI standards.

In unlicensed bands, what type of transmission method is required by regulators [238]

You are required by law to use spread spectrum transmission in unlicensed bands Spread spectrum transmission reduces propagation problems Especially multipath interference Spread spectrum transmission is NOT used for security in WLANs Normal Transmission versus Spread Spectrum Transmission

At 10 meters, a signal has a strength of 100 mW. About how strong will it be at 40 meters?

about 6 mW

In CSMA/CD+ACK, when a wireless NIC wishes to transmit, it listens for traffic. If there is traffic, it waits. When the traffic stops, it may transmit immediately.

always false

List the elements in a typical 802.11 LAN today. [241]

an 802.11 wireless LAN typically is used to connect a small number of mobile devices to a large wired LAN— typically, an Ethernet LAN—because the servers and Internet access routers that mobile hosts need to use usually are on the wired LAN.

802.11 standards are being developed to work in the ________ unlicensed band.

both 2.4 GHz and 5 GHz

Media access control governs transmission by ________.

both access points and wireless hosts

An extended service set (ESS) is a group of BSSs that ________.

both are connected to the same distribution system and have the same SSID

Beamforming can allow an access point to ________.

both direct power to individual clients and send signals to two different clients at the same time

What do we call a system whose channels have large bandwidth? [233]

broadband channels (fast)

Why is wider channel bandwidth good? [250]

doubling channel bandwidth doubles transmission speed. However, service bands have limited total bandwidth, so wider channels means fewer channels. ]

If two products both comply with 802.11 ac, they should have close to the same performance.

false

What is beamforming? [252]

having multiple antennas and changing the phase of waves coming from different antennas, an access point can focus signals toward individual hosts instead of broadcasting them,]

Frequency is measured in terms of ________.

hertz

If the signal strength from an omnidirectional radio source is 8 mW at 30 meters, how strong will it be at 120 meters, ignoring absorptive attenuation? Show your work. [228]

if S2 = S1 * (r1/ r2) 2 Then S2 = 8 mW* (30 meters /120 meters) 2 S2 = 8 mW* (1/4) 2 S2 = 8 mW* (1/16) S2 = 1/2 mw

How are shadow zones (dead spots) created? [229]

if there is a large or dense object (e.g., a brick wall), blocking the direct path between the sender and the receiver, the receiver may be in a ___________ (d___ spot), where the receiver cannot get the signal.

MIMO ________.

increases throughput

Wider channel bandwidth ________.

increases transmission speed

If more users move to an access point, this decreases ________.

individual throughput

Spread spectrum transmission is used in WLANs because ________.

it is required by regulators

Companies are moving to the 5 GHz band because there is ________ than in the 2.5 GHz band.

more bandwidth

Spread spectrum transmission is used in WLANs for ________.

more reliable transmission

The most serious problem with wireless transmission in WLANs is ________.

multipath interference

channels with small bandwidths

narrowbands (slow)

What propagation problem becomes worse as frequency increases?

neither inverse square law attenuation nor electromagnetic interference

A cellular telephone uses a(n) ________.

omnidirectional antenna

Mesh networking in 802.11 is likely to use ________.

only wireless devices

Access points take ________ from wireless devices and send them on to devices on the wired LAN. They also do the converse.

packets

Wireless access points typically link wireless clients to ________.

servers on the wired network

2.4 GHz and 5 GHz are ________.

service bands

What is an SSID? (Do not just spell out the acronym.) [243]

service set identifier (SSID). (Note that the term basic is not in the name.) Wireless hosts must know the SSID to associate with the access point.

Signals in a transmission usually ________.

spread over a range of frequencies

A channel has more bandwidth than is necessary given data transmission speeds requirements in ________ transmission.

spread spectrum

How many non-overlapping 20 MHz channels does the 5 GHz band support? [235-237]

the 5 GHz band provides between 11 and 24 non-overlapping 20 MHz channels, depending on the frequencies allocated to unlicensed operation in a country.

Wireless network standards operate at ________.

the data link layer

Access points in the same ESS communicate via ________.

the distribution system

If an 802.11n client tries to use an 802.11ac access point, ________.

they will communicate using 802.11n

The frequency spectrum extends ________.

to infinity

MIMO _____________.

transmits multiple signals in the same channel

WLANs normally use ________.

unlicensed bands

To transmit very rapidly in RADIO, you need ________.

wide bandwidth

In unlicensed bands, ________.

you can use radios wherever you please

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