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IEEE 802.11
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IRIRDA (Infrared Direct Access) :
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RF ,
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Industrial Scientific and Medical (ISM) bands 900 MHz (cell phones)2.4 GHz (Bluetooth technology) (low speed, short range)5 GHz (Wireless LAN) = 802.11
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(Mobility)(Scalability) hotspots(Flexibility) (Cost)
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RF (microwaves)(Security) (encryption)/(authentication)
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Q: emailA: Q:A:Q:PDAA:Q:A:
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Q: CDA: Q:A:Q:5.8GHzA:
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(Wireless Personal Area Networks, WPAN)(Wireless Local Area Networks, WLAN)(Wireless Wide Area Networks, WWAN)
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Wireless networks: (a) piconets/wireless PANsIEEE 802.15
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Wireless networks: (b) wireless LANIEEE 802.11 (WiFi)
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IEEE 802.11 IEEE 1997 6 , (Physical Layer) (Data Link Layer) Wi-Fi Wireless Fidelity 802.11 Wi-Fi (Alliance)
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WECA
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5 GHz RF 2.4 GHz ( 802.11b/g/n) 802.11 b/g 33% 802.11a
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2.4 GHz 11 Mbps 46 (150 ) / 96 (300)
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2.4 GHz 54 Mbps 802.11b 802.11b (Backwards compatible with 802.11b)
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2.4 GHz ( 5 GHz) 802.11g 802.11b ( 802.11a)
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(Wireless client) (Access point, AP)
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(Wireless Bridge) 25 miles RF
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802.11 2 (Infrastructure) (Ad Hoc)Infrastructure AP (Access Point, ) AP 2 , , , , AP
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(Antennas) ( (gain) ) = (Directional antenna)(Omni-directional antenna) Access Points
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(Basic Service Set, BSS)AP(Service Set Identifier, SSID)SSID(32)
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(Access Point, AP)(Independent Basic Service Set , IBSS)
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AP, , PCMCIA , Ad Hoc
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(Extended Service Set, ESS) AP ( BSS ) 10%
(BSS)(BSS)
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(channels) AP AP
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(Carrier Sense Multiple Access with Collision Avoidance) AP (Request to Send(RTS)) , AP Clear to Send (CTS) CTS ACK AP ACK AP ACK
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(Modes) (Mixed Mode) SSID WLAN SSID SSID (Wireless Channel) (auto locate)
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(STA) Access Point Windows XPWinXP(http://wlan.ncnu.edu.tw/wlanFAQ/winxp/winxp.htm)
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(stand-alone software) XP ping
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tune into (disable) SSID IP SSID
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MAC AP () MAC
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(credentials) (trustworthiness) (usernames) (passwords) WLAN
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AP (Internet Caf )
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AP : AP AP AP =
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EAP AP(RADIUS)
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Remote Authentication Dial-in User ServicesAP(username)
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WEP (Wired Equivalency Protocol) WEP 64 128 bits AP WEP
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WEP Wi-Fi Protected Access (WPA)WPA64 bits 256 bitsAP
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WLAN: IP Address MAC Address Port Numbers
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802.11b, g, n 2.4 GHz 5 GHz = 802.11a, ?/ (Total Cost of Ownership, TCO) (Site Survey) (interference)/
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(SSID, usernames, passwords) SSID MAC
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3 (Direct Sequence Spread Spectrum, DSSS) (Frequency Hopping Spread Spectrum, FHSS) (Infrared, IR) CSMA/CA
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()2
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(0 1) (Spreading Code) , , (Background Noise),
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, 2.4GHz , ,
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802.11 2 1 Mbps DBPSK (Differential Binary Phase Shift Keying) 2 Mbps DQPSK (Differential Quadrature Phase Shift Keying)
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, , , ,
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,, , , ,
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, , , , GFSK (Gaussian Frequency Shift Key), 1 Mbps, 2 Mbps
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, , ,
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802.11 DSSS()802.11 FHSS()79 802.11a OFDM()54 Mbps802.11b HR-DSSS()125.511 Mbps6Mbps802.11g OFDM()54 Mbps
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, Bluetooth SIG , , , , , , , , PDA (Personal Digital Assistant, )
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Bluetooth : (a)
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Bluetooth : (b)
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, 1 Mbps, 3 1
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, , , PDA ,
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(10 ) , 100 , , , , ,
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, , , , 1.5 , ,
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, , , , , PDA , , ,
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10 , 100 , 2.4 GHz , , IEEE 802.11, (1600 )
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(Piconet) 8 (active), (Master), (Client)AS: Active SlavePS: Parked SlaveSS: Standby Slave
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, , , , 2.4 GHz , ,
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( 1600 ) , , , , ,
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(), , , , , , ,
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2.4 GHz , 1600 , , , , , ,
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Piconet (a)
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Piconet (b)
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0111
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Sniff()(AMA)Hold() AMASCOPark() AMAbeaconmaster
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(Base Station, BS)(Mobile Station, MS)
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(Handoff)MSC(Roaming)
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(AMPS)(FDMA)
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AMPSGSM(TDMA)(FDMA)(IS)-95
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1900 MHz()(SMS)Internet
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144 Kbps384 Kbps2 Mbps2 GHz2 MHzInternet
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Internet Mobile Telephone, IMT-2000
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GSM (Global System for Mobile Communications, ), (European Telecommunications Standard Institute, ETSI) 1990 , ,
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, GSM 3 900 MHz 1800 MHz 1900 MHz GSM , , (Circuit Switch) , ,
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GSM 9.6 Kbps, , , 1998 GSM , GPRS
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GPRS (General Packet Radio Service) GPRS , GPRS GSM , ,
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, GPRS , , GSM , GPRS GSM
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GSM GPRS (Packet Switch) , 171.2 Kbps, 9.6 Kbps 20
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(Packet), , , , , ,
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, , , , GPRS 115 Kbps , GPRS , 64 Kbps , GSM
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1997 6 , (Ericsson) (Nokia)(Motorola) Phone.com , , , 9 WAP (Wireless Application Protocol, )
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WAP , , WAP, , , , WAP,
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WAP HTTP , (, PDA ) , HTTP (Hyper Text Markup Language, HTML), WAP , (Wireless Markup Language, WML)
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, , , , HTTP TCP/IP, WAP WDP (Wireless Datagram Protocol)WDP TCP/IP, WAP TCP/IP
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WAP WAP WAP (WAP Gateway)WDP WAP WAP , WAP , WAP WAP WAP , WML , WAP
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WAP WAP , , WAP Web , WML WAP , Web , WML , WAP
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WAP GPRS , HTTP ADSL , , , ADSL, HTTP ,
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OSI WAP 7 (Application Layer) 5 (Session Layer)GPRS 4 (Transport Layer) 1 (Physical Layer)