C07-Wireless_LANs

C07-Wireless_LANs - Mobile Communications Chapter 7:...

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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 7.1 Mobile Communications Chapter 7: Wireless LANs ± Characteristics ± IEEE 802.11 ± PHY ± MAC ± Roaming ± .11a, b, g, h, i … ± HIPERLAN ± Bluetooth / IEEE 802.15.x ± IEEE 802.16/.20/.21/.22 ± RFID ± Comparison
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 7.2 Mobile Communication Technology according to IEEE 802.11a Local wireless networks WLAN 802.11 802.11b 802.11i/e/…/w WiFi 802.11h 802.11g Personal wireless nw WPAN 802.15 802.15.4 802.15.1 802.15.2 Bluetooth ZigBee 802.15.4a/b 802.15.5 802.15.3 802.15.3a/b Wireless distribution networks WMAN 802.16 (Broadband Wireless Access) WiMAX + Mobility 802.20 (Mobile Broadband Wireless Access)
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 7.3 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) due to shared medium ± 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
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 7.4 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
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 7.5 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 ± Many different products
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 7.6 Comparison: infrastructure vs. ad-hoc networks infrastructure network ad-hoc network AP AP AP wired network AP: Access Point
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Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/
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C07-Wireless_LANs - Mobile Communications Chapter 7:...

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