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ch05_updated_hw - Homework Updated January 2007 CHAPTER 5...

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Homework Updated January 2007 CHAPTER 5 Wireless LANs (WLANs) Last Name: ____________________________________________________ First Name: ____________________________________________________ Due Date: __________________________________ Test Your Understanding 1. a) What type of computer primarily benefits from WLANs today? b) What are the dominant WLAN standards today? c) Are WLANs competitors for wired Ethernet LANs today? d) Why is a link to the main wired LAN needed in wireless networks? e) How can a firm create a large 802.11 WLAN? 2. a) Contrast the normal uses of 802.11 and Bluetooth WLANs. b) Compare 802.11 and Bluetooth distances. 3. a) Compare the speeds of 802.11, Bluetooth, UWB, and ZigBee. b) Compare the distance limits of 802.11, Bluetooth, and UWB. c) What technology could replace universal product code (bar code) tags on products? d) Describe mesh networking in 802.11. 4. a) What is a hertz? b) Are wavelengths or frequencies normally used to describe WLAN transmission? 5. a) Distinguish between omnidirectional and dish antennas in terms of operation. b) Under what circumstances would you use an omnidirectional antenna? c) Under what circumstances would you use a dish antenna? d) What type of antenna normally is used in WLANs? Why? 6. a) Which offers more reliable transmission characteristics—UTP or radio transmission? Chapter 5-1
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b) Which attenuate more rapidly with distance—signals sent though wired media or radio signals? c) If the signal strength from an omnidirectional radio source is 8 milliwatts (mW) at 30 meters, how strong will it be at 120 meters? d) How are shadow zones (dead spots) created? e) Why is multipath interference very sensitive to location? f) What is the most serious propagation problem in WLANs? g) List some sources of EMI. h) What propagation problems become worse as frequency increases? 7. Distinguish between a) the frequency spectrum, b) service bands, and c) channels. d) In radio, how can you send multiple signals without the signals interfering with one another? 8. a) Does a signal usually travel at a single frequency, or does it spread over a range of frequencies? b) What is channel bandwidth? c) If the lowest frequency in a channel is 1.22 MHz and the highest frequency is 1.25 MHz, what is the channel bandwidth? d) Why is large channel bandwidth desirable? e) What do we call a system whose channels have large bandwidth? 9. a) What is the Shannon equation? b) 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? c) Given their relative bandwidths, about how many times as much data is sent per second in television than in AM radio? d) What is the dividing line between narrowband and broadband speeds? 10. a) What is the golden zone in commercial mobile radio transmission? b) Why are lower frequencies not used? c) For what two reasons is operating at higher frequencies unattractive?
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