Thursday, August 20, 2009

WiFi

WiFi is the popular name for the wireless Ethernet 802.11b standard for WLANs. Wireline local area networks (LANs) emerged in the early 1980s as a way to allow collections of PCs, terminals, and other distributed computing devices to share resources and peripherals such as printers, access servers, or shared storage devices. One of the most popular LAN technologies was Ethernet. Over the years, the IEEE has approved a succession of Ethernet standards to support higher capacity LANs over a diverse array of media. The 802.11x family of Ethernet standards are for wireless LANs.

WiFi LANs operate using unlicensed spectrum in the 2.4GHz band. The current generation of WLANs support up to 11Mbps data rates within 300 feet of the base station. Most typically, WLANs are deployed in a distributed way to offer last-fewhundred- feet connectivity to a wireline backbone corporate or campus network. Typically, the WLANs are implemented as part of a private network. The base station.

equipment is owned and operated by the end-user community as part of the corporate enterprise network, campus or government network. In most cases, use of the network is free to end-users (subsidized by the community as a cost of doing business, like corporate phones).

Although each base station can support connections only over a range of a few hundred feet, it is possible to provide contiguous coverage over a wider area by using multiple base stations. A number of corporate business and university campuses havedeployed such contiguous WLANs. Still, the WLAN technology was not designed to support high-speed hand-off associated with users moving between base station coverage areas (i.e., the problem addressed by mobile systems).

In the last two years, we have seen the emergence of a number of service providers that are offering WiFi services for a fee in selected local areas such as hotels, airport lounges, and coffee shops.12 Mobilestar, which declared bankruptcy during the latter half of 2001, was one of the leaders in this area. In addition, there is a growing movement of so-called "FreeNets" where individuals or organizations are providing open access to subsidized WiFi networks.

In contrast to mobile, WLANs were principally focused on supporting data communications. However, with the growing interest in supporting real-time services such as voice and video over IP networks, it is possible to support voice telephony services over WLANs.

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