MOB 4 wireless LAN 2010 lập trình mobi

Mobile Internet 2010 Internet & Mobile Communications   Wireless LANs   Characteristics   Wi-Fi Research   IEEE 802.11   Introduction   PHY   MAC   Management   Wi-Fi Alliance and IEEE 802.11 2 Need for standardisation   Mobility  frequency regulation between countries is necessary : common frequency band   Limitation of battery usage   Limitation of interferences among different equipments (antennas can help)   configuration as seamless as possible   Compatibillity with existing LAN technologies   Seamless for users and applications (location aware applications…) Mobile Internet 2010 3 Characteristics of wireless LANs   Advantages –  very flexible within the reception area –  Ad-hoc networks without previous planning possible –  (almost) no wiring difficulties (e.g. historic buildings, firewalls) –  more robust against disasters like, e.g., earthquakes, fire - or users pulling a plug   Disadvantages –  typically very low bandwidth compared to wired networks (1-10 Mbit/s) –  many proprietary solutions, especially for higher bit-rates, standards take their time (e.g. IEEE 802.11) –  products have to follow many national restrictions if working wireless, it takes a vary long time to establish global solutions like, e.g., IMT-2000 Mobile Internet 2010 4 Design goals for wireless LANs –  global, seamless operation –  low power for battery use –  no special permissions or licenses needed to use the LAN –  robust transmission technology –  simplified spontaneous cooperation at meetings –  easy to use for everyone, simple management –  protection of investment in wired networks –  security (no one should be able to read my data), privacy (no one should be able to collect user profiles), safety (low radiation) –  transparency concerning applications and higher layer protocols, but also location awareness if necessary 7.2.1 Mobile Internet 2010 5 Comparison: infrared vs. radio transmission   Infrared –  uses IR diodes, diffuse light, multiple reflections (walls, furniture etc.)   Advantages –  simple, cheap, available in many mobile devices –  no licenses needed –  simple shielding possible   Disadvantages –  interference by sunlight, heat sources etc. –  many things shield or absorb IR light –  low bandwidth   Example –  IrDA (Infrared Data Association) interface available everywhere   Radio –  typically using the license free ISM band at 2.4 GHz   Advantages –  experience from wireless WAN and mobile phones can be used –  coverage of larger areas possible (radio can penetrate walls, furniture etc.)   Disadvantages –  very limited license free frequency bands –  shielding more difficult, interference with other electrical devices   Example –  WaveLAN, HIPERLAN, Bluetooth Mobile Internet 2010 Mobile Internet 2010 Internet & Mobile Communications   Wireless LANs   Characteristics   Wi-Fi Research   IEEE 802.11   Introduction   PHY   MAC   Management   Wi-Fi Alliance and IEEE 802.11 7 Wifi Research   Research shows 802.11 (aka Wi-Fi) is becoming an essential part of our everyday lives –  Research in the US reveals some factoids about the impact of Wi-Fi …   80% say Wi-Fi is more essential than their iPod   81% would rather see their favourite team lose than give up Wi-Fi for a week   90% would rather do without their daily Starbucks than their Wi-Fi –  … the bottom line is that Wi-Fi is affecting real people in their everyday lives Source: WFA/Kelton Research, July & October 2006 Andrew Miles - CISCO Andrew Miles - CISCO Mobile Internet 2010 8 Wifi Research   Wi-Fi has become popular based on products that are not optimised for wireless use … –  with apologies to all those in the PC industry   Not very usable while on the move   Not really suitable for many voice applications   Until recently, laptops were mainly an enterprise style product Andrew Miles - CISCO Mobile Internet 2010 9 Wifi Research   … and yet the Wi-Fi market reached over 200 millions chipsets per year in 2006 –  In 1997, the first IEEE 802.11 standard was ratified –  In 2005, over 150 million Wi-Fi devices were sold –  In 2006, over 200 million Wi-Fi devices were sold (33% growth rate) Enterprise APs Home/SOHO CE Phones PCs 0 40 80 120 160 200 2005 2006 Devices (million) Source: In-Stat Andrew Miles - CISCO Mobile Internet 2010 10 Microsoft Zune Sony mylo Nikon Coolpix Sony PS3 Nabaztag Nokia N series Wifi research   Wi-Fi is now being implemented in a wide variety of more interesting devices … Andrew Miles - CISCO Mobile Internet 2010 [...]... recently 32 Mobile Internet 2010 Reglementation of the ISM band Country Frequencies Band USA 2 ,40 0 – 2 ,48 5 GHz FCC Europe ETSI Japan MKK France ART 33 Mobile Internet 2010 2 ,40 0 – 2 ,48 35 GHz 2 ,47 1 – 2 ,49 7 GHz 2 ,40 0 – 2 ,48 35 GHz Reglementation in the ISM band 1) 241 2 6) 243 7 2) 241 7 7) 244 2 3) 242 2 12) 246 7 8) 244 7 4) 242 7 13) 247 2 9) 245 2 5) 243 2 USA (1-11) 34 11) 246 2 10) 245 7 Europe (1-13) Japan (1- 14) Each... spaced by 5MHz Mobile Internet 2010 14) 248 4 Reglementation in the ISM band   ISM Band –  –  –  Band divided in 14 channels of 20 MHz each Transmission (between sender and receiver) operated only on 1 channel Co-localisation of 3 networks in a same space channel 1 35 2 ,4 GHz Mobile Internet 2010 channel 7 83 MHz channel 13 2 ,48 35 GHz Channels allocation 13 1 7 13 36 Mobile Internet 2010 1 13 1 ... Equipments: 802.11 cards 26 Mobile Internet 2010 Equipments: Access points 27 Mobile Internet 2010 Equipments: Antennas 28 Mobile Internet 2010 IEEE 802.11 standard fixed terminal mobile terminal server infrastructure network access point application application TCP TCP IP IP LLC LLC LLC 802.11 MAC 802.11 MAC 802.3 MAC 802.3 MAC 802.11 PHY 802.11 PHY 802.3 PHY 802.3 PHY 29 Mobile Internet 2010 802.11 - Layers... 7.8.1 Mobile Internet 2010 Internet & Mobile Communications   Mobile Internet 2010 Wireless LANs   Characteristics   Wi-Fi Research   IEEE 802.11             Introduction Architecture PHY MAC Roaming Wi-Fi Alliance and IEEE 802.11 Frequency bands for 802.11x   For 802.11, Wi-Fi (IEEE 802.11b) and 802.11g –  –    ISM Band (Instrumentation, Scientific, Medical) - No licence required - 2 ,4 GHz... network 802.11 LAN   STA1 STA3 IBSS1 Direct communication within a limited range –  STA2 –  IBSS2 STA5 STA4 802.11 LAN 24 Mobile Internet 2010 Station (STA): terminal with access mechanisms to the wireless medium Independent Basic Service Set (IBSS): group of stations using the same radio frequency Architecture   Ad hoc Networks and Ad Hoc Mode Station B Station A 25 Mobile Internet 2010 Station C... 16 Mobile Internet 2010 Introduction IEEE 802.11   1990: launching of the project to create a wireless LAN - WLAN (Wireless Local Area Network) –  Goals: to offer a wireless connectivity to fixed workstations of mobile workstations   to allow fast deployment inside a local area   To permit the use of different frequency bands   –  17 2001: publication of the first International standard for wireless. .. up to 54 Mbits/s (UN-II band) 802.11g - speed up to 54 Mbits/s (bande ISM) 802.11h – dynamic selection of frequencies and power control (UN-II band) 802.11e - Quality of service 802.11f - Roaming 802.11i - security improvements 802.11n - MIMO … 802.11v - goal : create an interface of the higher layer which allow to manage wireless devices Mobile Internet 2010 Internet & Mobile Communications   Mobile... American Hotel & Lodging Melbourne Assn   13 Mobile Internet 2010 Wi-Fi Research Andrew Miles - CISCO 700 Not far from 1B! Devices (million) 600 500 40 0 CE … which means the promise of one billion chipsets sold in a year might not be far off! –  Voice –  300 –  200 100 14   0 2006 Mobile Internet 2010 2010 Both CE and Voice are forecast to make a big impact by 2010 They will enable even more use of Wi-Fi... Mobile Internet 2010 Wireless LANs   Characteristics   Wi-Fi Research   IEEE 802.11             Introduction Architecture PHY MAC Roaming Wi-Fi Alliance and IEEE 802.11 Comparison: infrastructure vs ad-hoc networks infrastructure network AP AP ad-hoc network 22 Mobile Internet 2010 wired network AP: Access Point AP 802.11 - Architecture of an infrastructure network 802.11 LAN 802.x LAN   Station... Internet & Mobile Communications   Wireless LANs   Characteristics   Wi-Fi Research   IEEE 802.11           Mobile Internet 2010 Introduction PHY MAC Management Wi-Fi Alliance and IEEE 802.11 Introduction IEEE 802.11   L'IEEE (Institute of Electrical and Electronics Engineers) has normalised several categories of local area networks –  Ethernet (IEEE 802.3) –  Token Bus (IEEE 802 .4) –  Token . electrical devices   Example –  WaveLAN, HIPERLAN, Bluetooth Mobile Internet 2010 Mobile Internet 2010 Internet & Mobile Communications   Wireless LANs   Characteristics   Wi-Fi. Token Bus (IEEE 802 .4) –  Token Ring (IEEE 802.5) Mobile Internet 2010 17 Introduction IEEE 802.11   1990: launching of the project to create a wireless LAN - WLAN (Wireless Local Area. Not far from 1B! Andrew Miles - CISCO Mobile Internet 2010 Mobile Internet 2010 Internet & Mobile Communications   Wireless LANs   Characteristics   Wi-Fi Research   IEEE 802.11