There are two volumes of the Bluetooth protocol specifications – Volume I being the Core Specification that defines the base Bluetooth technology and Volume II being the Profile Definitions that identifies the specific applications of the fundamental technology while ensuring that devices of various manufacturers are interoperable. For copies of the complete protocol specifications, you can download them from the official website of the Bluetooth Special Interest Group.
There are multiple individual layers in the Bluetooth protocol stack, which is common in these types of standards. An explanation of these protocol specifications would be very lengthy and it would be more practical to review the Bluetooth protocol specifications documentation for in-depth learning.
As a basic guide to protocol specifications, here is a look at the layers that make up the protocol stack. The physical layer is at the base level of the stack and its purpose is to implement the interface for physical communication to include radio frequency aspects like modulation.
Above this layer is the baseband layer, which like the physical layer has a single-integrated circuit implementation. In essence, this layer takes care of the implementation of the data transmission’s timing as well as sequencing and order from one device to another. Some Bluetooth devices today incorporate in one package this baseband layer functionality with the radio frequency functionality.
The next layer is called the Link Manager, wherein the real-time management of the behavior of wireless links happens. The Link Manager controls the device for the baseband and enables the discovery of existing Bluetooth service in order establish connection and communication between Bluetooth-enabled devices as they come within the network of each other.
The Link Manger’s upper portion, along with the layer above it, the Host Controller Interface (HCI) takes care of mechanisms for data transfer once connection is established.
Then above the HCI layer is the Logical Link Control and Adaptation Protocol or simple L2CAP, which controls and manages the flow of data.
The protocol stack divides above the L2CAP layer with the Application Layer link going either via the “Service Discovery Protocol” (SDP), the “Telephony Control Specification” (TCS), the Radio Frequency Communications (RFCOMM), or a Wireless Application Protocol (WAP), among other paths.
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