BlueTooth Technology

Bluetooth How to Build a Stone Patio the name given to a new technology standard using
short-range radio links, intended to replace the cable(s) connecting
portable Cheap Video Games 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 Latest Video Games 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
devices.

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 withthe lower layers. The Higher/upper-layer protocols consist of service-specific applicationsthat 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 supporttransferring of information between devices:

Core Protocols in Bluetooth:

Baseband: The Baseband and Link Control Popular Video Games enables the physical RFlink between Bluetooth forming a piconet. It provides two differentkind of physical links with their corresponding baseband packets,Synchronous Connection-Oriented and Asynchronous Connectionless whichcan be transmitted in a multiplexing manner on the same RFlink.Asynchronous Connectionless (ACL) packets are used for thetransmission of data only while Synchronous Connection-Oriented cancontain either audio or a combination of audio and information.

Link Manager Protocol: The link manager protocol is responsible forlink set-up between Bluetooth devices. This includes setting up ofsecurity 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 Bluetoothradio device, and the receiving device on the other end.

Logical Link Control and Adaptation Protocol: The Bluetooth logicallink control and adaptation protocol (L2CAP) adapts upper layerprotocols over the baseband. It can be thought to work in parallelwith LMP in difference that L2CAP provides services to the upper layerwhen the payload data is never sent at LMP messages.

Service Discovery Protocol: Using SDP, device information, servicesand 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 bitoriented protocol, defines the call control signaling for theestablishment of speech and data calls between Bluetooth devices.

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 transport mechanism.

Adopted Protocols:

PPP:PPP is the IETF Point-to-Point Protocol (Internet Atari TaskForce, IETF Directory List of RFCs) and PPP-Networking is the means oftaking 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 developedby the Infrared Data Association (IrDA) to exchange data in a simple and automatic way.

Advantages:

Using peer-to-peer connectivity, Bluetooth technologysimplifies personal area wireless connections, enabling all digitaldevices to communicate automaticaly. Bluetooth technology alsoprovides fast, secure voice and data transmissions. The range forconnectivity 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 canprotect data by using error-correction methods and provides a hightransmission rate. It is possible encryption and authentication forprivacy in the transmitted data.In Bluetooth ad hoc networking enables personal devices toautomatically exchange information and synchronize with each other.

Jith is an Electrical and Electronic Engineer by profession from Southern india. he has good experience in sensors, Data acquisition systems, communication protocols etc, and can be contact through crsjith@gmail.com

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