Bluetooth is the name given to a new technology standard using
short-range radio links, intended to replace the cable(s) connecting
portable and fixed electronic devices. The standard defines a uniform
structure for a wide range of devices to communicate with each other.
Its important features of Bluetooth are robustness, low complexity,
low power and low cost. Bluetooth is considered a wireless PAN
technology that offers fast and reliable transmission for both voice
and data. Bluetooth offers wireless access to LANs, PSTN, the mobile
phone network and the Internet for home or office and other hand held
A complete Bluetooth system will require these elements:
- An RF portion for collecting and sending data or information:
- A module with a baseband microprocessor for processing function
- Memory module
- An interface to the electronic device (such as a mobile phone, camera, or PC)
The lower-layer Bluetooth protocols are normally embedded in the
baseband module, and the host processor must support the upper-layer
protocols (like file transfer). In other words, the RF/baseband
solution provides the means to communicate with the host, but need to
implement a connection interface, as well as any upper-layer
protocols, to use applications supported by the final product.
The higher/upper layers of the Bluetooth technology called as the
Bluetooth profiles and these are nothing but a set of protocols. These
protocols are optimized for particular applications. In the case of
file transfer between two devices, it requires interoperability among
devices. Each of the linked devices needs to have similar applications
ensures interoperability across a spectrum of devices.
The Bluetooth stack: It has the following components:
- RF portion for reception and transmission
- Baseband portion with micro controller
- Link control unit
- Link manager to support lower-layer bluetooth audio module protocols
- Interface to the host device
- Host processor to support upper-layer protocols
- L2CAP to support upper-layer protocols
The radio frequency (RF) portion provides the digital
signal-processing (DSP) component of the system,
and the baseband micro controller processes these signals.
The link controller handles all the baseband functions and supports
the link manager. It sends and receives data, identifies the sending
device, performs authentication, and determines the type of frame to
use for sending a transmissions. The link controller also directs how
devices listen for transmissions from other devices and can move
devices into sleep state in order to save power.
The link manager, located on top of the link controller, controls
setup, authentication, link configuration, and other low-level
protocols. Together, the baseband and the link manager establish
connections for the network.
The host controller interface (HCI) communicates the lower-layer
protocols to the host device(Like mobile phone, hand held PC etc).The host contains a processor.
- it supports the upper-layer protocols and communicates with the lower layers. The Higher/upper-layer protocols consist of service-specific applications that must be integrated into the host application as explained above. RFCOMM protocol, which allows for the emulation of serial ports over the L2CAP, which is also an important part of Bluetooth. The Service Discovery Protocol (SDP) gives the required services and the properties and characteristic of the service that a particular Bluetooth device is made for.