The Bluetooth core system covers the four lowest layers and associated protocols defined by the Bluetooth specification as well as one common service layer protocol, the Service Discovery Protocol (SDP) and the overall profile requirements are specified in the Generic Access Profile (GAP). A complete Bluetooth application requires a number of additional service and higher layer Protocols. The lowest three layers are sometimes grouped into a subsystem known as the Bluetooth controller. This is a common implementation involving a standard physical communications interface between the Bluetooth controller and remainder of the Bluetooth system including the L2CAP, service and higher layers (known as the Bluetooth host.) Although this interface is optional the architecture is designed to allow for its existence and characteristics The Bluetooth core system protocols are the Radio (RF) protocol, Link Control (LC) protocol, Link Manager (LM) protocol and Logical Link Control and Adaptation protocol (L2CAP), all of which are fully defined in subsequent parts of the Bluetooth specification. In addition the Service Discovery Protocol (SDP) is a service layer protocol required by all Bluetooth applications.
Bluetooth technology operates in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.485 GHz, using a spread spectrum, frequency hopping, full-duplex signal at a nominal rate of 1600 hops/sec
Logical Link Control and Adaptation protocol (L2CAP) Link Manager (LM) protocol Host to Controller Interface (HCI)