Bluetooth Protocol stack/layers
The protocol architecture of the bluetooth consists of following in a bluetooth protocol stack:
• Core protocols consisting 5 layer protocol stack viz. radio,baseband,link manager protocol,logical link control and adaptation protocol, service discovery protocol.
• Cable replacement protocol,RFCOMM
• Telephony Control Protocols
• Adopted protocols viz. PPP,TCP/UDP/IP,OBEX and WAE/WAP
Radio: This protocol specification defines air interface, frequency bands, frequency hopping specifications,
modulation technique used and transmit power classes.
Baseband: Addressing scheme, packet frame format , timing and power control algorithms required for establishing connection between bluetooth devices within piconet defined in this part of protocol specification.
Link Manager protocol: It is responsible to establish link between bluetooth devices and to maintain the link between them. This protocol also includes authentication and encyption specifications. Negotiation of packet sizes between devices can be taken care by this.
Logical link control and adaptation protocol: This L2CAP protocol adapts upper layer frame to baseband layer frame format and vice versa. L2CAP take care of both connection oriented and connectionless services.
Service discovery protocol: Service related queries including device information can be taken care at this protocol so that connection can be established between bluetooth devices.
Cable replacement protocol
Serial ports are popular to provide serial communication between devices. Bluetooth uses RFCOMM as cable replacement protocol. RFCOMM functions as virtual serial port and does transport of binary digital data bits. It basically emulates RS232 specifications over bluetooth physical layer.
Telephony Control Protocols
TCS-BIN is the protocol used here which is a bit oriented one. It specifies call control signals and mobility management procedures. These signals take care of establishing speech and data calls.
These protocols are already defined by other standard bodies which are incorporate without any change in the bluetooth protocol stack architecture. The protocols are PPP,TCP/UDP/IP,OBEX and WAE/WAP.
PPP is a point to point protocol used to transfer IP datagrams.
TCP/UDP and IP are part of basic TCP/IP model, for more refer our article on Basics of OSI and TCPIP layers.
OBEX is a object exchange protocol developed by IrDA and it is similar to HTTP. It is a session level protocol.
WAE and WAP provides Wireless Application Environment and WAP provides Wirelesss Application Protocol.