Increasing demand for wireless technology means that the radio frequencies must be carefully managed and allocated by governments to satisfy all the different users and to prevent interference between them. (You may remember the UK Government's auction of 3G radio licences in Spring 2000 which raised approximately £22.5 billion.)
Before transmitting radio signals, organisations must usually obtain a licence permitting them to use a specified frequency or band of frequencies. However, one band of radio frequencies is available internationally for unlicensed users. These are the frequencies lying between 2.4000 GHz and 2.4835 GHz. These frequencies – usually referred to simply as the 2.4 GHz frequency band – are collectively known as the industrial, scientific and medical (ISM) radio band. (Some countries also allocate additional frequencies for unlicensed users.)
In the remainder of this section we introduce two wireless standards that are designed to operate within the ISM band of radio frequencies. These are WiFi, developed by The Institute of Electrical and Electronics Engineers (IEEE) and covered by the IEEE 802.11 family of wireless LAN standards, and Bluetooth, developed by the Bluetooth Special Interest Group (SIG) and covered by the IEEE 802.15 family of wireless PAN standards.