Tài liệu Mob 4 wireless lan 2010

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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 Need for standardisation             2 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 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 3 Mobile Internet 2010 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 4 7.2.1 Mobile Internet 2010 Comparison: infrared vs. radio transmission   Infrared –    Advantages –  –  –    –  –  –  –    IrDA (Infrared Data Association) interface available everywhere Mobile Internet 2010 experience from wireless WAN and mobile phones can be used coverage of larger areas possible (radio can penetrate walls, furniture etc.) Disadvantages –  –    typically using the license free ISM band at 2.4 GHz Advantages Example –  5   simple, cheap, available in many mobile devices no licenses needed simple shielding possible interference by sunlight, heat sources etc. many things shield or absorb IR light low bandwidth Radio –  Disadvantages –    uses IR diodes, diffuse light, multiple reflections (walls, furniture etc.)   very limited license free frequency bands shielding more difficult, interference with other electrical devices Example –  WaveLAN, HIPERLAN, Bluetooth 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 Wifi Research Andrew Miles - CISCO   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 7 Mobile Internet 2010 Andrew Miles - CISCO Wifi Research Andrew Miles - CISCO   Wi-Fi has become popular based on products that are not optimised for wireless use … –  .. with apologies to all those in the PC industry       8 Mobile Internet 2010 Not very usable while on the move Not really suitable for many voice applications Until recently, laptops were mainly an enterprise style product Wifi Research Andrew Miles - CISCO   200 Devices (million) 160 –  120 –  80 –  40 9 … and yet the Wi-Fi market reached over 200 millions chipsets per year in 2006 0 Source: In-Stat 2005 Mobile Internet 2010 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 Wifi research Andrew Miles - CISCO   Wi-Fi is now being implemented in a wide variety of more interesting devices … Microsoft Zune 10 Sony mylo Mobile Internet 2010 Nabaztag Nikon Coolpix Nokia N series Sony PS3 … including lots of Wi-Fi & Wi-Fi/cellular converged phone devices … Andrew Miles - CISCO 11 Mobile Internet 2010 Wifi Research Andrew Miles - CISCO   … with some of the new devices actually used for voice (and not just data) … –  –  –  Numerous Wi-Fi carrier voice and data deployments are underway, and others expected during 2007 and 2008 Wi-Fi with UMA is the predominant voice approach today, although SIP solutions also exist Examples of voice deployments include:       12 Mobile Internet 2010 BT Fusion:voice & data in the home/office network at more than 2,000 Openzone hotspots Orange Unik for Professionals: provides Wi-Fi to GSM handoff, and includes unlimited use for Wi-Fi calls NTT DoCoMo: SIP-based voice for large enterprise customers Wi-Fi Research Andrew Miles - CISCO   … based on access in many locations outside the home or office … –  143k+ hot spots in 132 countries     –  500+ muni deployments in 29 countries   –  Source: JiWire (12 March 2007) Other sources indicate 200k+ hot spots Source: Tropos & WFA 82% of US hotels offer Wi-Fi Source: American Hotel & Lodging Melbourne Assn   13 Mobile Internet 2010 Wi-Fi Research Andrew Miles - CISCO 700 Not far from 1B! Devices (million) 600 500 400 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 both in all market segments One billion chipsets is forecast by 2012 Enterprise APs Home/SOHO CE Phones PCs 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 Ring (IEEE 802.5) 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 LAN developped by the IEEE organisation. Mobile Internet 2010 Introduction IEEE 802.11   Frequencies are chosen in the 2,4 GHz Band (as for Bluetooth technology) –  –    No need for licensing Band in not completely free in many countries Communications –  Can be direct from terminal to terminal   –    It is then impossible to relay frames from one terminal to another With an Access Point which relays all the traffic Transmission rates vary depending on coding technics which are used and of the bandwidth allocated. 18 Mobile Internet 2010 Introduction IEEE 802.11   Access Method to the physical layer (MAC protocol - Medium Access Control) –  –  –  Quite complex Many available options on the radio interface Access Technics derived from CSMA/CD Carrier Sense Multiple Access/Collision Detection, used to define the access in wired networks   Problem: In wireless networks it is impossible to detect collisions as for Ethernet LANs.   –  Introduction of a new protocol : CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) 19 Mobile Internet 2010 IEEE 802.11   802.11 - Main Standard (june 1997) –    802.11x - Amendements –  –  –  –  –  –  –  –  –  –  20 Le groupe de travail concentre maintenant ses efforts pour produire des standards pour des WLAN à grande vitesse 802.11b - speed up to 11 Mbits/s (ISM band) 802.11a - speed 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
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