NETWORK TOPOLOGY
Bluetooth devices are generally organized into groups of two to eight devices called piconets,
consisting of a single master device and one or more slave devices. A device may additionally
belong to more than one piconet, either as a slave in both or as a master of one piconet and a
slave in another. These bridge devices effectively connect piconets into a scatternet. A diagram of a Bluetooth scatternet is shown in Fig. 2.
Bluetooth operates in the unlicensed ISM frequency band, generally cluttered with signals from other devices: garage door openers, baby monitors, and microwave ovens, to name just a few. To help Bluetooth devices coexist and operate reliably alongside other ISM devices, each Bluetooth piconet is synchronized to a specific frequency hopping pattern. This pattern, moving through 1600 different frequencies per second, is unique to the particular piconet. Each frequency hop is a time slot during which data packets are transferred. A packet may actually span up to five time slots, in which case the frequency remains constant for the duration of that transfer.