ter 15 WMANs, WLANs, and WPANs Where Bluetooth Got Its Name In the tenth century, there was a king in Denmark named Harald Blatand, which trans- lates to Harold Bluetooth in English. King Blatand was instrumental in uniting warring fac- tions in parts of what is now Norway, Sweden, and Denmark. He was renowned for his ability to help people communicate. Fast-forward to the twentieth century: During the formative stage of the IEEE 802.15.1 trade association, the effort required a code name. One evening, as the members were discussing European history and the future of wireless technology, they came upon the notion of naming the technology after King Blatand: Just as he had united warring fac- tions, Bluetooth technology is designed to allow collaboration between differing indus- tries, such as the computing, mobile phone, and automotive markets. The code name stuck, and the technology today lives up to its name. Even the Bluetooth logo has an interesting origin. To read about it, visit http:// bluetooth.com/Bluetooth/SIG/Who/History/. whenever they come within range, with the actual distance allowed depending on the power class of the devices. There are three power classes: Class 1-Class 1 devices consume 100 milliwatts of power and support the longest range, up to 300 feet (100 m). This class of device is readily available. Class 2-Class 2 devices consume 2.5 milliwatts of power and allow trans- mission over a distance of up to 30 feet (10 m). It is the most common class of device. Class 3-Class 3 devices consume 1 milliwatt of power and supports trans- mission over a range from 4 inches to 3 feet (10 cm to 1 m). This class of device is the least common. The initial focus of Bluetooth was ad hoc interoperability between mobile phones, headsets, and PDAs, but today it is also seeing application in sensor-based networks. Most Bluetooth devices are recharged regularly. Bluetooth uses FHSS (discussed in Chapter 13) and splits the 2.4GHz ISM band into 79 1MHz channels. Bluetooth devices hop among the 79 channels 1,600