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
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 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.
L2CAP: 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.
The ACL Link: Bluetooth uses five logical channels to support
transferring of information between devices:
Core Protocols in Bluetooth:
- Baseband: The Baseband and Link Control layer enables
the physical RF link between Bluetooth forming a piconet. It provides
two different kind of physical links with their corresponding
baseband packets, Synchronous Connection-Oriented and Asynchronous
Connectionless which can be transmitted in a multiplexing manner
on the same RF link.Asynchronous Connectionless (ACL) packets
are used for the transmission of data only while Synchronous Connection-Oriented
can contain either audio or a combination of audio and information.
- Link Manager Protocol: The link manager protocol is responsible
for link set-up between Bluetooth devices. This includes setting
up of security functions like authentication and encryption by
generating, exchanging and checking of link and encryption keys
and the control, negotiation of baseband packet sizes and duty
cycles of the Bluetooth radio device, and the receiving device
on the other end.
- Logical Link Control and Adaptation Protocol: The Bluetooth
logical link control and adaptation protocol (L2CAP) adapts upper
layer protocols over the baseband. It can be thought to work in
parallel with LMP in difference that L2CAP provides services to
the upper layer when the payload data is never sent at LMP messages.
- Service Discovery Protocol: Using SDP, device information,
services and the characteristics of the services can be queried
and after that, a connection between two or more Bluetooth devices
can be established.
Telephony and Cable Replacement Protocol:
- Telephony Control protocol: Binary (TCS Binary or TCS
BIN), a bit oriented protocol, defines the call control signaling
for the establishment of speech and data calls between Bluetooth
- RFCOMM:It is a serial line emulation protocol and is
based on ETSI 07.10 ( European Telecommunications Standardization
Institute ) specification. This protocol emulates RS-232 control
and data signals over Bluetooth baseband, providing both transport
capabilities for upper level services that use serial line as
- PPP:PPP is the IETF Point-to-Point Protocol (Internet
Engineering Task Force, IETF Directory List of RFCs) and PPP-Networking
is the means of taking IP packets to/from the PPP layer and placing
them onto the LAN.
- TCP/UDP/IP: TCP/IP/PPP is used for the all Internet Bridge
usage scenarios in Bluetooth 1.0 and for OBEX in future versions.
UDP/IP/PPP is also available as transport for WAP.
- OBEX Protocol: IrOBEX (Short name is OBEX) is a session
protocol developed by the Infrared Data Association (IrDA) to
exchange data in a simple and automatic way.
Using peer-to-peer connectivity, Bluetooth technology simplifies
personal area wireless connections, enabling all digital devices
to communicate automaticaly. Bluetooth technology also provides
fast, secure voice and data transmissions. The range for connectivity
is less than 10 meters, and line of sight is not required. The Bluetooth
radio unit can functions even in noisy radio environments, ensuring
audible voice transmissions in severe conditions. It can protect
data by using error-correction methods and provides a high transmission
rate. It is possible encryption and authentication for privacy in
the transmitted data.
In Bluetooth ad hoc networking enables personal devices to automatically
exchange information and synchronize with each other.