Interoperability
Interoperability refers to the ability of two devices to communicate with each other. Now, any Bluetooth device features one or more applications, known as profiles. For one Bluetooth device to be able to communicate with another, the two devices must have at least one shared profile. If, for instance, your Bluetooth device features the profile object exchange, you can exchange business cards with any other Bluetooth device that has the object exchange profile. Some other examples of profiles are: file transfer, serial port, and network.
Device discovery
When two or more Bluetooth devices are within range, a link can be established. However, first of all a Bluetooth device needs to discover the other Bluetooth devices that are active within its range. This operation is called device discovery. When another Bluetooth device responds, it supplies necessary information, some of which concerns its identity: the device name (eg. Adam) or the unique device address (eg. 00:50:CD:3A:4B:69). A link can now be established to the discovered device.
Wireless networks
Piconet
At the very heart of the Bluetooth technology is the idea of forming small wireless networks known as piconets. When a Bluetooth device has established a link to one or more other devices, a piconet has been formed. The device that initiates a connection acts as the master. The other devices are slaves. The master controls all traffic in the piconet. Communication between slaves can only take place via the master. In the below example of a piconet, the laptop (master) transmits to the handheld computer (slave 1) and the mobile phone (slave 2):
One master, up to 255 slaves
As already mentioned, in a piconet there can only be one master. Furthermore, up to seven slaves can be active. However, there can be additional slaves which are not active but remain synchronized to the piconet. Such slaves are referred to as parked. A parked device can very quickly become active and begin communicating in the piconet. By swapping active and parked slaves, you can increase the number of slaves virtually connected to the piconet from seven to 255 devices
Bluetooth PC Card | Bluetooth Introduction • 4 |