Overview of Bluetooth Pairing
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10/16/2008
Bluetooth® is a short range wireless technology which enables wireless data transmission between two Bluetooth–enabled devices located nearby each other.
The Bluetooth stack is comprised of a layered architecture that facilitates data transport between Bluetooth-enabled devices. Each protocol is implemented by an architectural layer known as a profile. Each profile implements a different protocol and contributes to the ability to establish a link and facilitate data transport between devices that support the Bluetooth stack. Wireless networking between Bluetooth–enabled devices is achieved through a physical channel between each Bluetooth–enabled device, through which one or more logical channels are established. Using the logical channel, Bluetooth devices perform logical transport through the profile specific to the type of data being transmitted. Logical links established over the physical channel are managed by Logical Link Control and Adaptation Protocol (L2CAP).
For in depth discussion of Bluetooth architecture, obtain and read the Bluetooth v2.0 Specification.
Bluetooth–enabled devices, including the Windows Embedded CE powered device, host the Bluetooth stack along with the profiles required for the types of data communications that the Bluetooth–enabled device wants to conduct through a Bluetooth wireless connection.
Bluetooth Profiles
A Bluetooth profile defines the requirements necessary for one Bluetooth–enabled device to exchange data with another specific type of Bluetooth–enabled device.
Bluetooth technology defines a wide range of profiles that describe many different use cases. Windows Embedded CE supports the hands–free profile (HFP), which describes how a gateway device (mobile phone) can be used to place and receive calls for a hands–free device (Windows Embedded CE). The Advanced Audio Distribution Profile (A2DP) describes how stereo quality audio can be streamed from an audio source (for example, a media storage device) to an audio sink (for example, a wireless headset). A2DP defines the protocols and procedures that realize distribution of high-quality audio content in either mono or stereo through a Bluetooth wireless connection using Asynchronous connection-oriented (ACL) channels. ACL is a logical transport used to exchange asynchronous data and both Link Manager Protocol (LMP) and L2CAP control signaling.
Bluetooth Pairing
If one Bluetooth–enabled device is in discovery mode and discovers another Bluetooth–enabled device nearby, it can query for its services and choose to establish a Bluetooth link, or a 'pairing relationship', with the other Bluetooth–enabled device. Establishing a Bluetooth link with another Bluetooth–enabled device is also known as pairing.
The following illustration is a visual representation of Bluetooth wireless communication between two Bluetooth–enabled devices during service discovery:
.gif "Bluetooth pairing")