Bluetooth layer model
The layer model ofBluetooth essentially consists of three functional areas. The transmission-related functional area is formed by the radio technology and the baseband technology. They are used to access the air interface and the physical data channel.
The functional level of the Bluetooth layer model
The middle functional level of the Bluetooth layer model is formed by the link manager and the hostcontroller interface( HCI). This functional area takes care of the communication with the higher layers, the applications and the target computer in which the Bluetooth unit is located. The Link Management Protocol( LMP) and the Host Controller Interface (HCI) are available for this communication. The Link Manager Protocol (LMP) takes care of connection establishment, security during transmission and communication with the end device.
In the functional area of the application, the application interface and the functional elements are defined in the form of the Bluetooth profiles. When a connection is established between two Bluetooth devices, the devices exchange their Bluetooth profiles and thus define which services they can provide for the respective other partner and which data and commands they require to do so.
The Bluetooth protocol stack
The Bluetooth protocol stack supports wireless communication in the physical layer, as well as connectionless and connection-oriented services with one data channel and three voice channels, or alternatively a single channel over which both data and voice can be transmitted. The Bluetooth standard defines transmission rates of 432.6 kbit/s for each direction in symmetrical duplex transmission; in asymmetrical operation, it is 723.3 kbit/s for the downstream and 57.6 kbit/s is available for the upstream. In addition, voice signals can be transmitted at 64 kbit/s. Bluetooth uses a 64-kbit/s CVSD speech coding scheme, which offers much higher error tolerance than Adaptive Delta Pulse CodeModulation( ADPCM).