Overview
Bluetooth standard offers basic rate (BR) or enhanced data rate (EDR) and Bluetooth Low Energy (LE) support. Devices that can support BR/EDR and Bluetooth LE are referred to as dual-mode devices. Typically, in a Bluetooth system, a mobile phone or laptop computer acts as a dual-mode device.
Devices that only support Bluetooth LE are referred to as single-mode devices where the low power consumption is the primary concern for application development, such as those that run on coin cell batteries.
This article focus on:
- Detailed description of the BR/EDR profiles.
- Bluetooth LE profiles.
1.1 Bluetooth protocol stack
The Bluetooth protocol stack consists of two sections, the controller and the host, derived from the original Bluetooth core specification where the two sections were often implemented separately.
1.1.1 BR/EDR protocol stack
The BR/EDR protocol stack architecture is illustrated in Figure 1.
The controller section includes the Physical Layer (PHY), Link Layer (LL) and Host-Controller Interface (HCI).
- 1) The physical layer (PHY) is the lowest layer of the Bluetooth protocol stack to manage physical channels and links.
- 2) The link layer (LL) is used to control the radio link between two devices, handling matters such as link establishment, querying device abilities and providing power control.
- 3)The host control interface (HCI) provides a means of communication between the host and controller using a standardized interface.
The host includes various communication protocols, as described below.
- 1) The logical link control and adaption protocol (L2CAP) provides data encapsulation services to the upper layers that enable logical end-to-end data communication.
- 2) The radio frequency communication (RFCOMM) is a set of transport protocols on top of the L2CAP protocol, providing emulated RS-232 serial ports.
- 3) The generic access profile (GAP) defines the generic procedures related to discovery of Bluetooth devices and link management aspects of connecting to Bluetooth devices.
- 4) The service discovery protocol (SDP) is used to allow devices to discover the supported services, and parameters to use to connect to them.
- 5) The hands-free profile (HFP) allows hands-free kits to control the mobile phone of calling functions and provide the voice connection between devices.
- 6) The object exchange (OBEX) is a communications protocol that facilitates the exchange of binary objects between devices.
- 7) The phonebook access profile (PBAP) defines the procedures and protocols to exchange phonebook objects between devices.
- 8) The Advanced Audio Distribution Profile (A2DP) defines how multimedia audio is streamed from one device to another via Bluetooth connection
- 9) The audio/video distribution transport protocol (AVDTP) is used by the advanced audio distribution profile to stream music to stereo headsets over the L2CAP channel intended for video distribution profile in the Bluetooth transmission.
- 10) The audio/video control transport protocol (AVCTP) is used to transport the command/response messages exchanged for the control of distant A/V devices over point-to-point connections.
- 11) The audio/video remote control profile (AVRCP) defines the features and procedures required in order to ensure interoperability between Bluetooth devices with audio/video control functions in the audio/video distribution scenarios.
- 12) The serial port profile (SPP) emulates a serial cable to provide a simple substitute for existing RS-232.
1.1.2 Bluetooth LE protocol stack
The Bluetooth LE protocol stack architecture is shown in Figure 2.
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