PHY data rate from 1 to 2 or 3 Mbps. A Bluetooth PAN can support up to eight devices in a piconet, with one device acting as master and up to seven as active slave devices. Piconets can be linked to form the so-called scatternets through the sharing of common devices, since a device can be both a master in one piconet and a slave in another. Each master device manages a piconet with a capacity of 720 kbps and a scatternet can have a much higher distributed capacity, under the control of multiple master devices. Bluetooth supports a wide variety of different types of devices and usage models, from mobile phone headsets to PDA synchronisation. Typically different usage models will call on different parts of the Bluetooth protocol stack. A profile is a vertical slice through the Bluetooth protocol stack (Figure 10-1), and represents the required protocols for a particular usage model. Profiles provide the basis for device interoperability and any given Bluetooth device may support a number of different usage models and therefore different profiles. Examples of the most important profiles are given in Table 10-2. Bluetooth achieves low component cost and extended battery life by settling for limited transmission range and modest data rates. Nevertheless, Chapter Ten Applications Protocols RFCOMM L2CAP Figure 10-1: Bluetooth Application Profiles Table 10-2: The Main Bluetooth Profiles Profile Description Personal area networking Enables general Internet protocol (IP) networking (including security) over an ad-hoc piconet. Synchronisation profile Enables the exchange of personal information such as calendar and address book data between devices. Basic printing profile Enables simple printing from a device to a printer. Specific printer drivers are not required in the sending device as the Bluetooth-enabled printer has the capability to decode the data sent to it to produce the required format. File Transfer Profile Enables a device to perform file management operations on another device's file system, including transfe