30-04-2011, 01:54 PM
PRESENTED BY:
Madhina Basha
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Bluetooth Technology
Introduction to Bluetooth Technology
Bluetooth is a radio frequency specification for short range, point to point and point to multi point voice and data transfer ,which is developed for Personal Area Network (PAN).
Eliminates wires and cables between both stationary and mobile devices
Bluetooth technology works as an universal medium to bridge the existing data networks.
It work as a peripheral interface for existing devices and provide a mechanism to form short ad hoc network of connected devices away from fixed network infrastructures.
Why it’s name is Bluetooth?
Bluetooth was named for the 10th Century Viking king , Harald Blatand (A.K.A., Bluetooth) who peacefully united all the tiny island kingdoms of Denmark, southern Sweden, and southern Norway into one country .
In keeping with its namesake, Bluetooth, the new low-cost radio technology, is designed to unite or connect all different types of devices to effectively work as one.
How Bluetooth Technology Work ?
The technology of Bluetooth centers around a 9mm x 9mm microchip, which functions as a low cost and short range radio link.
Bluetooth Technology provide a 10 meter personal bubble that support simultaneous transmission of both voice and data for multiple devices.
Topology
There are two types of topology for Bluetooth
Piconet
Scatternet
Piconet :
Up to 8 devices can be connected in a piconet, and up to 10 piconets can exist within the 10 meter bubble.
Each piconet has a unique hopping pattern/ID
Each master can connect to 7 simultaneous or 200+ inactive slaves per piconet
Scatternet:
Bluetooth Architecture
Bluetooth Layers
Radio layer:
This is the lowest layer in the Bluetooth protocol stack.
It defines the requirement for a Bluetooth transceiver operating in 2.4GHz ISM band.
Bluetooth uses a technique called frequency hopping spread spectrum (FHSS) in establishing radio links with other Bluetooth devices.
Bluetooth hops 1600times per second.
A device uses a frequency for only 625 µs before it hops to another frequency.
Standard hop values are 79hops, which are spaced at an interval of 1MHz.
Transmitter characteristics:
Power Class 1: long range devices(~100m), with max output power of 20dBm
Power Class 2: ordinary range devices (~10m), with max output power of 4dBm
Power Class 3: short range devices(~10cm), with max output power of 0dBm
Modulation Characteristics:
To transfer bits to a signal Bluetooth module uses sophisticated version of FSK called GFSK(Gaussian Frequency Shift Keying).
fc = 2402+n n=0,1,2,3,……,78
frequency in megahertz
Baseband layer:
Responsible for channel coding/decoding, timing and managing error correction and all of the other low level details necessary in a Bluetooth link.
Master/slave
Devices in a connection are either master or slave.Communication is only possible between a master and its slaves.
The hopping sequence is unique for piconet and it is determined by the Bluetooth device address of the master.
Master-slave Communication
Master and Multi Slave Communication
The Baseband handles three types of links:
SCO(Synchronous Connection-Oriented)
The master maintains the SCO page link by reversed slots at regular intervals.
SCO page link mainly carries voice information.
SCO packets are used for 64kB/s speech transmission.
Polling-based(TDD) packet transmissions
In this page link type one slot is of 0.625msec(max 1600 slots/sec)
ACL(Asynchronous Connection-less)link
Bluetooth Packet format
Link Manager Protocol
The LMP is used by the page link managers for page link set up and control.
Responsible for creating the link, monitering their health and tear down connections and logical links.
Link controller states introduced to carry out these tasks.
Link setup
Authentication
Link configuration
Connection
LMP consists of a number of PDU which are sent from one device to another.
HCI(Host Controller Interface):
HCI provides a command interface to the baseband page link controller and page link manager and access to hardware status and control registers.
L2CAP(Logical Link Control and Adaptation Protocol):
It manages the high level aspects of each connection
It is responsible for converting the format of data as necessary between the APIs and the lower level Bluetooth protocols.
L2CAP permits higher level protocols and applications to transmit and receive L2CAP data packets up to 64 kilobytes in length
Radio Frequency Communication(RFCOMM)
RFCOMM takes care of communication between two devices.
RFCOMM basically has to accommodate two kinds of devices:
Communication end-points such as computers or printers.
Devices that are a part of communication channel such as Modems
Service Discovery Protocol(SDP):
SDP provides a means for application to discover, which services are provided b or available through Bluetooth device.
Telephony Control Protocol Spec(TCS):
Basic function of this layer is call control and group management for gateway serving multiple devices.
Application Program Interface(API):
These are software module which connect the host application program to the Bluetooth communications system.
ADVANTAGES OF BLUETOOTH TECHNOLOGY
No line of site restrictions as with IrDA.
power consumption makes integrated in battery powered devices very practical.
2.4 GHz radio frequency ensures worldwide operability.
Tremendous momentum not only within the computer industry but other industries like cellular telephones and transportation.