Chapter 7 Wireless Networks I
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
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
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
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
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