wide, chal- lenging traditional service providers and business models. Initially, WLANs were meant to be an augmentation, not a replacement, of wired LANs and premises tele- phone systems. WLANs were deployed in enterprise or corporate locations where there might be a number of factors that limited or prevented wired systems from being installed. Today, we see much greater utility for WLANs, as evidenced by the WLANs emergence of thousands of hotspots around the world. In some cases, it is cheaper to deploy wireless in an office than to replace a crumbling old token-ring cable plant with shiny new Ethernet. In general, WLANs operate over short ranges, anywhere from 10 to 500 feet (3 to 150 m), so their coverage areas are microcells or picocells. Like many other telecom technologies, WLANs have gone through various generations, and the data rates supported reflect that evolution. The early products were quite limited, operating at only 1Mbps to 11Mbps, with the actual throughput being 50% or less of the maximum rate quoted. But the newer standards support data rates of up to 54Mbps, with the actual throughput being up to 32Mbps, and emerging standards promise 100Mbps to 200Mbps. From the standpoint of an enterprise user, the primary applications for early WLANs were to reduce the costs associated with moves, adds, and changes; simplify installation procedures; and enable mobility within the building or campus environ- ment. In the realm of the public domain today, the primary application for WANs is simply mobility-to accommodate the rapidly growing number of road warriors as well as consumers who want to communicate, work, and play anytime, anywhere. WLANs typically operate on unlicensed frequency bands, either the 2.4GHz or 5GHz bands. They do not require line-of-sight conditions, which is a very desirable feature. The key element of a WLAN is a wireless access point (WAP), or base sta- tion. WAPs are connected to an Ethernet hub or server and transmit a radio fre- quency over an area of several hundred feet, wh