Bluetooth MAC layer
Bluetooth MAC layer consists of Link Manager Protocol(LMP) and Logical Link Control and Adaptation Protocol(L2CAP).
Bluetooth standard defines five different types of logical data channels based on different payload traffic carried by them. They are link control, link manager,user asynchronous,user isochronous and user synchronous. Link Control channel carry information such as ARQ,flow control and payload characterization.
Bluetooth modes of operation
During the connection state bluetooth device can be in one of the four modes which include
active mode,sniff mode,hold mode and park mode.
In the Active mode, bluetooh device actively participates in the channel.
In the Sniff mode, bluetooth slave device will not listen on all the received slots but listen only specified slots for messages meant for it.
In the Hold mode, the bluetooth device does not transmit data for long time.
In the Park mode,the bluetooth device will have little activity to be performed and hence will consume very low power.
Link Manager Protocol(LMP)
LMP protocol is used to establish the link and to control the link.
Link Control (LC) provides the reliability to Link Manager Protocol.
LM PDUs are sent in single slot packets.
PDU = Opcode(7bits), transaction ID(1bit), information contents
Logical Link Control and Adaptation Protocol(L2CAP)
This L2CAP protocol like LLC takes care of link layer protocol services between the entities. It provides services to upper layers and rely on lower layer for flow control as well as error control.L2CAP makes use of ACL links and does not use SCO links.
L2CAP provides two type of services connectionless and connection mode services. Connectionless type provide reliable datagram delivery service. Connection mode type provide service using HDLC protocol.