17-WirelessLANs

17-WirelessLANs - William Stallings Data and Computer...

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Unformatted text preview: William Stallings Data and Computer Communications 8 th Edition Chapter 17 Wireless LANs Overview • A wireless LAN uses wireless transmission medium • Used to have high prices, low data rates, occupational safety concerns, and licensing requirements • Problems have been addressed • Popularity of wireless LANs has grown rapidly Applications - LAN Extension • Saves installation of LAN cabling • Eases relocation and other modifications to network structure • However, increasing reliance on twisted pair cabling for LANs — Most older buildings already wired with Cat 3 cable — Newer buildings are prewired with Cat 5 • Wireless LAN to replace wired LANs has not happened • In some environments, role for the wireless LAN — Buildings with large open areas • Manufacturing plants, stock exchange trading floors, warehouses • Historical buildings • Small offices where wired LANs not economical • May also have wired LAN — Servers and stationary workstations Single Cell Wireless LAN Configuration Multi-Cell Wireless LAN Configuration Applications – Cross-Building Interconnect • Connect LANs in nearby buildings • Point-to-point wireless link • Connect bridges or routers • Not a LAN per se — Usual to include this application under heading of wireless LAN • Applications - Nomadic Access • Link between LAN hub and mobile data terminal — Laptop or notepad computer — Enable employee returning from trip to transfer data from portable computer to server • Also useful in extended environment such as campus or cluster of buildings — Users move around with portable computers — May wish access to servers on wired LAN Infrastructure Wireless LAN Applications – Ad Hoc Networking • Peer-to-peer network • Set up temporarily to meet some immediate need • E.g. group of employees, each with laptop or palmtop, in business or classroom meeting • Network for duration of meeting Add Hoc LAN Wireless LAN Requirements • Same as any LAN — High capacity, short distances, full connectivity, broadcast capability • Throughput: efficient use wireless medium • Number of nodes:Hundreds of nodes across multiple cells • Connection to backbone LAN: Use control modules to connect to both types of LANs • Service area: 100 to 300 m • Low power consumption:Need long battery life on mobile stations — Mustn't require nodes to monitor access points or frequent handshakes • Transmission robustness and security:Interference prone and easily eavesdropped • Collocated network operation:Two or more wireless LANs in same area • License-free operation • Handoff/roaming: Move from one cell to another • Dynamic configuration: Addition, deletion, and relocation of end systems without disruption to users Technology...
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This note was uploaded on 02/10/2012 for the course CSC 411 taught by Professor Simmons during the Spring '08 term at S. Alabama.

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17-WirelessLANs - William Stallings Data and Computer...

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