The Bluetooth Protocol Architecture

Bluetooth network technology connects mobile devices wirelessly over a short-range to form a personal area network (PAN). The Bluetooth architecture has its own independent model with a stack of protocols, instead of following the standard OSI model or TCP/IP model.

The protocols in the Bluetooth standard can be loosely grouped into the physical layer, data link layer, middleware layer, and application layer as shown in the following diagram −

Protocols in the Bluetooth Protocol Architecture

• Physical Layer − This includes Bluetooth radio and Baseband (also in the data link layer.

  • Radio − This is a physical layer equivalent protocol that lays down the physical structure and specifications for transmission of radio waves. It defines air interface, frequency bands, frequency hopping specifications, and modulation techniques.

  • Baseband − This protocol takes the services of radio protocol. It defines the addressing scheme, packet frame format, timing, and power control algorithms.

• Data Link Layer − This includes Baseband, Link Manager Protocol (LMP), and Logical Link Control and Adaptation Protocol (L2CAP).

  • Link Manager Protocol (LMP) − LMP establishes logical links between Bluetooth devices and maintains the links for enabling communications. The other main functions of LMP are device authentication, message encryption, and negotiation of packet sizes.

  • Logical Link Control and Adaptation Protocol (L2CAP) − L2CAP provides adaption between upper layer frame and baseband layer frame format. L2CAP provides support for both connection-oriented as well as connectionless services.

• Middleware Layer − This includes Radio Frequency Communications (RFComm) protocol, adopted protocols, SDP, and AT commands.

  • RFComm − It is short for Radio Frontend Component. It provides a serial interface with WAP.

  • Adopted Protocols − These are the protocols that are adopted from standard models. The commonly adopted protocols used in Bluetooth are Point-to-Point Protocol (PPP), Internet Protocol (IP), User Datagram Protocol (UDP), Transmission Control Protocol (TCP), and Wireless Application Protocol (WAP).

  • Service Discovery Protocol (SDP)− SDP takes care of service-related queries like device information so as to establish a connection between contending Bluetooth devices.

  • AT Commands − ATtention command set.

• Applications Layer − This includes the application profiles that allow the user to interact with the Bluetooth applications.