Generally, the ability to transmit radio signals over the air is tightly regulated. Government bodies, such as the U.S. Federal Communications Commission (FCC), determine what technologies can be used to transmit over the air and who is allowed to operate those technologies (see Figure 1). They do this latter part by issuing licenses, usually for money, to organizations interested in transmitting wirelessly. These licenses, which are often hard to obtain, are required in part to prevent multiple network operators from interfering with each other.
The advantage of Wi-Fi, over other wireless technologies such as WiMAX (which we will cover in Chapter 7), is that no licenses are needed to set up and operate a Wi-Fi network. All that it takes to become a network operator is to buy the equipment and plug it in.
Clearly, the array of allocations within the spectrum is bewildering. And network operators for licensed wireless technologies must be aware of the rules for at least the part of the spectrum that their technology works in, to avoid violating the terms of the license. But, thankfully, all of this is taken care of automatically when 802.11 technology is used. Wi-Fi operates in two separate stretches (or "bands") of the radio spectrum, known in the United States as the Industrial, Scientific, and Medical (ISM) bands, and the Unlicensed National Information Infrastructure (U-NII) bands. These bands have a long history, and it is no coincidence that voice lead the way. Many people first became familiar with the concept of unlicensed radio transmissions when 900MHz cordless telephones were introduced. These phones require no licenses, but have a limited range and do only one thing—connect the call back to the one and only one base station. However, the power from using wireless to avoid having to snake cables throughout the house and allowing callers to walk from room to room revealed the real promise of wireless and mobility.
For enterprises, the benefits of the freedom from using unlicensed spectrum are clear. Removing the regulatory hurdles from wireless brings the requirements for setting up wireless networks down to the same level as for wireline networks. Expanding the network, or changing how it is configured, requires no permission from outside authorities (ignoring the physical requirements such as building codes necessary to pull cables). There is no concern that a regulatory agency might reject a Wi-Fi network because of too many neighboring allocations. Enterprises gain complete control of their air, to deploy it how they see fit.
Because being unlicensed gave the potential for every user to be her own network operator, wireless networking settled into the hands of the consumer, and that is where we will continue the story.
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