Where Wi-Fi Operates
Wi-Fi uses part of the radio spectrum - the 2.4-gigahertz (GHz) band reserved by the Federal Communications Commission for unlicensed use. This means that although the equipment you purchase has been approved by the FCC (and its regulatory counterparts if you're outside the United States), you don't need a license to operate it. Nor are you assured of exclusive use of the band. Wi-Fi uses a transmission technique called spread spectrum, which broadcasts over a swath of different frequencies at different times. The standard was designed to offer three clear channels that don't overlap, so that you can cover a wider area. This is especially popular in dense urban areas or offices. As signal strength weakens or interference increases, Wi-Fi can drop down to three slower speeds and continue sending and receiving data: 5.5, 2 and 1 Mbps. The two slower speeds also work with older equipment that predates Wi-Fi but isn't widely used. Outside the United States, different countries have approved different parts of the 2.4-GHz band for unlicensed use, so some channels allowed in the United States are illegal elsewhere (and vice versa). Access points bought in the United States might require software changes to work elsewhere. Client adapters - PC and PCI Cards, for instance - tune into whichever channels are in use, so they can almost always be used worldwide.