Bluetooth Protocol Stack Tutorial

Cell phones frequently use Bluetooth technology.

Bluetooth technology uses short-range radio links to replace the cables connecting portable and fixed devices. It defines a uniform communication structure that is robust, low power and low cost yet easy to use. The development of Bluetooth technology, originally intended for peripherals, is increasingly driven by the desire to give mobile devices access to the Internet, LANs and other networks. The Bluetooth standard was created to facilitate communication across platforms to create a global communication standard, and it has achieved its goal. Both the core and the profiles for Bluetooth specifications are available, royalty free, from the Bluetooth website.

Instructions

1. 

   Microwave ovens operate on the same frequency as Bluetooth devices.

   Start with the bottom layer. In Bluetooth technology that is the spread spectrum radio that operates in the unlicensed ISM band at around 2.4 GHz. This is the same frequency used by microwave ovens.

2. 

   Just like building blocks, the structure is in layers.

   Consider that the next layer, the baseband, controls the radio and sets the frequency hop sequence. The baseband also provides lower-level encryption and packet handling. Two kinds of links are established at this level: Synchronous Connection Oriented (SCO) links used for voice, and Asynchronous Connection Less (ACL), which are used for data that does not need a synchronous link.

3. 

   Bluetooth hands-free devices are popular.

   Examine your device structure. The Link Manager Protocol (LMP) along with the baseband establish and control links between devices and are usually implemented by the device. The Host Controller Layer (HCL) is the interface between the hardware and the Logical Link Control and Adaptation Protocol (L2CAP), which is usually on the host. If the L2CAP is also on the device the HCL may not be needed, as the L2CAP can communicate directly with the LMP.

4. 

   There are Bluetooth USB devices.

   Recognize that the Host Controller Interface (HCI) is on the device and gets the communications over the physical bus. The HCI driver is on the host and formats the date for the Host Controller on the Bluetooth device.

5. 

   There are many uses for Bluetooth technology.

   Create the interface for the software and the device. This interface can be direct to the L2CAP or it can use protocols like RFCOMM, TCS and SDP. Because the Bluetooth Special Interest Group (SIG) was created by Ericsson, IBM, Intel, Nokia and Toshiba to create an open specification for short-range wireless connectivity that would work across platforms, it accepts a range of protocols.

Tips & Warnings

• To encourage the establishment of a cross-platform communication system, the core Bluetooth specifications and profile are royalty free and available from the "Get Technical Zone" on the official Bluetooth site (see Resources). Take advantage of the information that is freely offered there.

• Do not expect to create your first interface without encountering difficulties. One of the key elements to the success of Bluetooth technology is simplicity, however, that only extends so far. Take one layer at a time and make sure your foundation is balanced before taking it to the next level.

References

• Wayne State University: Bluetooth Primer
• Palowireless: Bluetooth Tutorial

Resources

• Bluetooth: Get Technical