BlueTooth Technology
admin | VPN Story | November 13th, 2007 | No Comments »
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
devices.
A complete Bluetooth system will require these elements:
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:
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 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 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.
- Advantages:
- 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.
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
[tags]Bluetooth,Point-to-Point,PPP,RF,baseband,peer-to-peer,communication,IrOBEX,L2CAP,RFCOMM,Link[/tags]
