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Bluetooth Stack Architecture (Windows CE 5.0)

Windows CE 5.0
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The protocol stack makes up the core portion of the Bluetooth implementation. This stack enables devices to locate each other and establish a connection. Through this connection, devices can exchange data and interact with one another through various applications.

The following image map shows the supported layers within the Bluetooth stack. To link to topics that provide information about the elements in the image map, move your pointer over the element, and then choose the element.


OBEX (Object Exchange) is an object exchange protocol that is implemented on top of Winsock over Bluetooth and IRDA transports. For more information, see Object Exchange Protocol.

  • Obex client module: Obexapi.dll
  • Obex server module: Obexsvr.dll

TDI (Transport Driver Interface), in the Microsoft® Windows® CE operating system (OS) architecture, is an interface that serves as an adaptation layer to Winsock-based user APIs. It isolates the highly asynchronous callback-based architecture of the stack presenting a Windows Sockets Specification 1.1 interface.

COM Port Emulation, in Windows CE, enables virtual COM ports to be created over RFCOMM channels. It hosts dial-up and LAN access profiles. For more information, see Creating a Connection to a Remote Device Using a Virtual COM Port. The port emulation facility is included in Btd.dll.

SDP (Service Discovery Protocol) is a Bluetooth service discovery protocol that handles publishing and discovery of services running on top of the Bluetooth stack. The port emulation is included in Btd.dll.

  • SDP client module: Btdrt.dll
  • SDP server module: Btd.dll

RFCOMM (Serial Cable Emulation Protocol) is Bluetooth's adaptation of the TS07.10 protocol. It serves as a base for COM port emulation facilities and derived point-to-point protocols. Multiplexing and flow control between devices and applications are also implemented here. The RFCOMM layer is included in Btd.dll.

PAN (Personal Area Network) profile defines procedures to support standard IP-based network services deployed over the Bluetooth transport layer. For more information, see Personal Area Networking (PAN) Profile.

HID (Human Interface Device) profile defines procedures to support human interface devices such as keyboard and mouse. For more information, see Human Interface Device (HID) Profile.

L2CAP (Logical Link Control and Adaptation Protocol) is a lower connection-based Bluetooth communication protocol that implements multiplexing. L2CAP does not implement flow control. It relies on a reliable device-to-device baseband link provided by Bluetooth hardware. The L2CAP layer is included in Btd.dll.

HCI (Host Controller Interface) is a basic interface to Bluetooth hardware, responsible for controller management, link establishment, and maintenance. For more information, see Host Controller Interface. The HCI layer is included in Btd.dll.

Bluetooth Universal Transport Manager (BthUniv) is an intermediate transport driver between the HCI layer and the transport layer. It detects the Plug and Play (PnP) device and loads the appropriate transport driver. For more information, see Supported HCI Transport Drivers. The Bluetooth Universal Transport Manager is in Bthuniv.dll.

HCI Transport Layer is a transport layer that delivers HCI commands to the Bluetooth hardware. For more information, see Bluetooth HCI Transport Layer. For more information about the modules that implement this layer, see Supported HCI Transport Drivers.

LMP (Link Manager Protocol) is the protocol that handles link establishment between Bluetooth devices, which include authentication and encryption.

BB (Baseband) enables the physical radio frequency (RF) link between Bluetooth units that form a piconet.

Each layer, with the exception of the HCI transport, is implemented as a separate entity that exposes its interfaces up and down through tables of callbacks. Each interface is well defined. There are no other interrelationships between parts of the stack; every layer is replaceable.

See Also

Bluetooth Protocol Stack | Bluetooth Stack Implementation in Windows CE | Bluetooth


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