Saturday, 7 May 2011
It is well to aquaint oneself with the terminology used in Bluetooth, if one is to understand the descriptions on these webpages. One could say that there are 3 types of connections in Bluetooth, as shown to the right:
• a) Single-slave
• b) Multi-slave (up to 7 ”slaves” on one master)
• c) Scatternet
A collection of devices connected via Bluetooth technology in an ad hoc fashion. A piconet starts with two connected devices, such as a portable PC and a mobile phone. The limit is set at 8 units in a piconet (that´s why the required address-space is limited to 3 bits). All Bluetooth devices are peer units and have identical implementations. However, when establishing a piconet, one unit will act as a master for synchronization purposes, and the other unit(s) will be slave(s) for the duration of the piconet connection.
Two or more independent and non-synchronized piconets that communicate with each other. A slave as well as a master unit in one piconet can establish this connection by becoming a slave in the other piconet. It will then relay communications between the piconets, if the need arises.
The device in a piconet whose clock and hopping sequence are used to synchronize all other devices in the piconet. The master also numbers the communication channels.
All devices in a piconet that are not the master (up to 7 active units for each master).
A 3-bit Media Access Control address used to distinguish between units participating in the piconet.
Devices in a piconet which are regularly synchronized but do not have MAC addresses. They are woken up by the Master with a ”beacon signal”.
Sniff mode and hold mode:
Devices that are synchronized to a piconet, and which have temporarily entered power-saving modes in which device activity is lowered. They keep their MAC-addresses.
To support slaves, the Master establishes a beacon channel when one or more slaves are parked. This channel consists of one beacon slot, or a train of equidistant beacon slots transmitted at constant time interval.