1、WIRELESS LAN In just the past few years, wireless LANs have come to occupy a significant niche in the local area network market. Increasingly, organizations are finding that wireless LANs are an indispensable adjunct to traditional wired LANs, as they satisfy requirements for mobility, relocation, a
2、d hoc networking, and coverage of locationsdifficult to wire. As the name suggests, a wireless LAN is one that makes use of a wireless transmission medium. Until relatively recently, wireless LANs were little used; the reasons for this included high prices, low data rates, occupational safety concer
3、ns, and licensing requirements. As these problems have been addressed, the popularity of wireless LANs has grown rapidly. In this section, we first look at the requirements for and advantages of wireless LANs, and then preview the key approaches to wireless LAN implementation. Wireless LANs Applicat
4、ions There are four application areas for wireless LANs: LAN extension, crossbuilding interconnect, nomadic access, and ad hoc networks. Let us consider each of these in turn. LAN Extension Early wireless LAN products, introduced in the late 1980s, were marketed as substitutes for traditional wired
5、LANs. A wireless LAN saves the cost of the installation of LAN cabling and eases the task of relocation and other modifications to network structure. However, this motivation for wireless LANs was overtaken by events. First, as awareness of the need for LAN became greater, architects designed new bu
6、ildings to include extensive prewiring for data applications. Second, with advances in data transmission technology, there has been an increasing reliance on twisted pair cabling for LANs and, in particular, Category 3 unshielded twisted pair. Most older building are already wired with an abundance of Category 3 cable. Thus, the use of a wireless LAN to replace wired LANs has not happened to any great extent. However, in a number of environments, there is a role for the wireless LAN as an alter
