WIRELESS LOCAL AREA NETWORK WLAN Essay Research — страница 2

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Reduced Cost-of-Ownership: While the initial investment required for wireless LAN hardware can be higher than the cost of wired LAN hardware, overall installation expenses and life-cycle costs can be significantly lower. Long-term cost benefits are greatest in dynamic environments requiring frequent moves and changes. Scalability: Wireless LAN systems can be configured in a variety of topologies to meet the needs of specific applications and installations. Configurations are easily changed and range from peer-to-peer networks suitable for a small number of users to full infrastructure networks of thousands of users that enable roaming Safety: The output power of wireless LAN systems is very low, much less than that of a hand-held cellular phone. Since radio waves fade rapidly

over distance, very little exposure to RF energy is provided to those in the area of a wireless LAN system. Wireless LANs must meet stringent government and industry regulations for safety. No adverse health affects have ever been attributed to wireless LANs. 4.Applications of Wireless LAN?s Wireless LANs frequently augment rather than replace wired LAN networks-often providing the final few meters of connectivity between a wired network and the mobile user. The following list describes some of the many applications made possible through the power and flexibility of wireless LANs: ?Doctors and nurses in hospitals are more productive because hand-held or notebook computers with wireless LAN capability deliver patient information instantly. ?Consulting or accounting audit teams or

small workgroups increase productivity with quick network setup. ?Students holding class on a campus greensward access the Internet to consult the catalog of the Library of Congress. ?Network managers in dynamic environments minimize the overhead caused by moves, extensions to networks, and other changes with wireless LANs. ?Training sites at corporations and students at universities use wireless connectivity to ease access to information, information exchanges, and learning. ?Network managers installing networked computers in older buildings find that wireless LANs are a cost-effective network infrastructure solution. ?Trade show and branch office workers minimize setup requirements by installing pre-configured wireless LANs needing no local MIS support. ?Warehouse workers use

wireless LANs to exchange information with central databases, thereby increasing productivity. ?Network managers implement wireless LANs to provide backup for mission-critical applications running on wired networks. ?Senior executives in meetings make quicker decisions because they have real-time information at their finger-tips. 5.Customer Considerations Customers Consider the following qualities before a purchasing a Wireless LAN. ?Range Coverage ?Throughput ?Integrity and Reliability ?Compatibility with the Existing Network ?Interoperability of Wireless Device ?Licensing Issues ?Security ?Cost ?Battery Life for Mobile Platforms 6.Types of Wireless LAN?s There are two types of Wireless LANs: Ad-hoc Networks This network can be set up by a number mobile users meeting in a small

room. It does not need any support from a wired/wireless backbone. There are two ways to implement this network. Broadcasting/Flooding Suppose that a mobile user A wants to send data to another user B in the same area. When the packets containing the data are ready, user A broadcasts the packets. On receiving the packets, the receiver checks the identification on the packet. If that receiver was not the correct destination, then it rebroadcasts the packets. This process is repeated until user B gets the data. Temporary Infrastructure In this method, the mobile users set up a temporary infrastructure. But this method is complicated and it introduces overheads. It is useful only when there is a small number of mobile users. Infrastructure Networks This type of network allows users

to move in a building while they are connected to computer resources. In an infrastructure network, a cell is also known as a Basic Service Area (BSA). It contains a number of wireless stations. The size of a BSA depends on the power of the transmitter and receiver units, it also depends on the environment. A number of BSAs are connected to each other and to a distribution system by Access Points (APs). A group of stations belonging to an AP is called a Basic Service Set (BSS) 7.Wireless LAN Technology Manufacturers of wireless LANs have a range of technologies to choose from when designing a wireless LAN solution. Each technology comes with its own set of advantages and limitations. Spread Spectrum Most wireless LAN systems use spread-spectrum technology, a wideband radio