Bluetooth Protocol Stack

Radio Layer

• critical for the physical communication between Bluetooth devices
• Ensures reliable and efficient data transmission by defining RF characteristics, modulation schemes, frequency bands, and error correction method
• uses frequency hopping and adaptive mechanisms that allows Bluetooth to coexist with other wireless technologies

Baseband Layer

• Above the Radio Layer
• Responsible for managing physical channels and links
• handles low-level operations of Bluetooth communication, such as packet formation, addressing, timing, and error correction

Link Manager Protocol (LMP)

• responsible for managing the establishment, maintenance, and security of links between Bluetooth devices
• operates directly above the Baseband layer and handles various control functions to ensure proper link configuration and management

Host Controller Interface (HCI)

• serves as an interface between the Host (typically the operating system or Bluetooth stack software ) and the Bluetooth Controller(the hardware responsible for handling the physical layer and baseband operations)
• defines standardized set of commands, events, and data structures for communication between the Host and the Controller, allowing the Host to control and configure the Bluetooth hardware

Logical Link Control and Adaptation Protocol(L2CAP)

• operating above the Baseband layer and providing an abstraction layer for higher-layer protocols
• enables high-layer protocols to exchange data packets over Bluetooth connections, offering features such as segmentation and reassembly, multiplexing, and quality of service (Qos) negotitation

RFCOMM (Radio Frequency Communication)

• provides emulation emulation of serial ports over Bluetooth
• enables serial communication betwen Bluetooth-enabled devices, allowing application to communication using a familiar serial port interface
• useful for legacy application that rely on serial port communication and need to migrate to Bluetooth without significant changes to their software architecture

Service Discovery Protocol(SDP)

• responsible for discovering and describing services offered by Bluetooth devices within a LAN
• enables Bluetooth devices to identify available services, determine their characteristics, and establish connections with compatible services for data exchange or interaction