Transcript
The Technology
Ayesha SaeedQurat-ul-AinFatima Syed
Amna Naveed
Fatima Jinnah Women University,The Mall Rawalpindi Pakistan
What is Bluetooth?
“Bluetooth wireless technology is an open specification for a low-cost, low-power, short-range radio technology for ad-hoc wireless communication of voice and data anywhere in the world.”
One of the first modules (Ericsson) A recent module
Bluetooth Goals & Vision
• Originally conceived as a cable replacement technology
• Short-Range Wireless Solutions
• Open Specification
• Voice and Data Capability
• Worldwide Usability
Present wireless technology like Infra Red data communication has two problems :
1)Line of Sight
2) One to One
BLUETOOTH OVERCOMES THESE PROBLEMS
Bluetooth vs. IRD
Bluetooth
• Point to Multipoint
• Data & Voice
• Easier Synchronization due to
omni-directional and no LOS
requirement
• Devices can be mobile
• Range 10 m
IRD• Point to point
• Intended for Data Communication
• Infrared, LOS communication
• Both devices must be stationary,
for synchronization
• Range 1 m
Logo
• A Scandinavian firm originally designed the logo at the time the SIG (Special Interest Group) was formally introduced to the public
• The logo unites the Runic alphabetic characters "H", which looks similar to an asterisk, and a "B", which are the initials for Herald Bluetooth
Bluetooth History
When does it appear?
1994 – Ericsson study on a wireless technology to link mobile phones & accessories.5 companies joined to form the Bluetooth Special Interest Group (SIG) in 1998.First specification released in July 1999.
Timeline
1994 : Ericsson study complete / vision
1995 : Engineering work begins
1997 : Intel agrees to collaborate
1998 : Bluetooth SIG formed: Ericsson, Intel, IBM, Nokia & Toshiba
1999 : Bluetooth Specification 1.0A SIG promoter group expanded
2000 : Bluetooth Specification 1.0B, 2000+ adopters
2001 : First retail products released, Specification 1.1
2003 : Bluetooth Specification 1.2
2005 : Bluetooth Specification 2.0
Different Versions of Bluetooth
• Bluetooth 1.1: Offers Only some Basic Features. The first Bluetooth core
specification version 1.1 was introduced in 1998
• Bluetooth 1.2: New features to eliminate radio frequency interference
through frequency hopping and added greater security. It was released in 2003.
• Bluetooth 2.0: In 2004,Bluetooth version 2.0 + EDR(Enhanced data rate) was
introduced
Different Versions of Bluetooth
• Bluetooth 2.1: The SIG then introduced version 2.1, which improved
pairing without the need for a PIN, requires even lower power consumption, and offers more security.
• Bluetooth 3.0: Created in 2009, Bluetooth 3.0 added the ability to use a
Wi-Fi connection to increase data transmission speeds
• Bluetooth 4.0: Most recent is Bluetooth 4.0. Its major feature is Bluetooth
Low Energy, essentially strong power management skills.
The Basic Idea
• Bluetooth is a standard for a small , cheap radio chip to be plugged into computers, printers, mobile phones, etc
• Bluetooth chip is designed to replace cables. Information normally carried by the cable, is transmitted at a special frequency to a receiver Bluetooth chip.
• These devices can form a quick ad-hoc secure “piconet” and start communication.
• Connections in the “piconets” can occur even when mobile.
Requirements
• Low cost as cables – chip $5• Secure as cables – must support authentication and
encryption• Must support both data and voice.• Must connect to a variety of devices.• Must be able to function in a noisy environment.• Data rates – 721kbps , using the 2.45Ghz radio
frequency band –I.S.M (Industrial, scientific and medical)
• Must support many simultaneous and private “piconets”.
• Must be low power, compact and global.
Bluetooth Classes
• If you wish to communicate over the 100m range, you will need a class 3 Bluetooth device at both ends.
• If you wish to communicate over the 10m range, you can have a class 2 device at both ends.
Piconet
• A piconet is an ad-hoc computer network linking a wireless user group of devices using Bluetooth technology protocols.
A collection of devices connected via Bluetooth technology in an ad hoc fashion
Piconet….cont.
• A piconet starts with two connected devices, and may grow to eight connected devices.
• Master• Slaves (up to 7)
One of the Bluetooth devices as a main controlling unit or MASTER unit
Other devices that follow the master unit are SLAVE units.
Piconet….cont.
• The master device acts as the hub, meaning the slave devices must communicate through the master device in order to communicate with each other. In most piconets, the computer serves as the master device.
• one master device interconnect with up to seven active slave devices using a three-bit MAC address. In addition to this a further 255 slave devices can be connected in an "inactive", or "parked" mode, which can be made "active" at any time by the master device.
Each active device within a piconet is identifiable by a 3-bit active device address.
• A master is the only one that may initiate a Bluetooth communication link. However, once a link is established, the slave may request a master/slave switch to become the master. Slaves are not allowed to talk to each other directly. All communication occurs within the slave and the master.
• Where higher number of Bluetooth enabled devices need to communicate for data exchange, the master Bluetooth-enabled device is capable of swapping the active slaves for the parked slaves in a round robin sequence, normally based of priority assigned.
How Piconet Works?
• Bluetooth piconets utilize frequency hopping.
• 79 frequencies are used and The frequency hopping is done at a rate of 1600 times a second.
• Devices use an assigned frequency of 2.45 GHz, a frequency set aside for this purpose by the ISM(Industrial Scientific and Medical) frequency band.
Working…Cont.
• Each piconet has a unique master with it’s >>Unique Bluetooth device address (BD_ADDR) >>Clock• Therefore, each piconet has its unique frequency hopping
sequence.• When a connection is initiated by Bluetooth enabled devices,
the master device’s clock along with the device address (BD_AAR) is transmitted to the slave devices in a packet known as Frequency-Hop Synchronization Packet (FHS packet).
The device address of the master device is used to calculate the sequence of frequency hops which all devices within a
piconet, follow. The clock of the master device assigns the sequence of the frequency hops.
All devices within a piconet use the difference between their own native clock and the master’s native clock to make use of
particular frequency in order to transmit or receive radio signals on a particular moment.
• Using this method, the Bluetooth devices within a piconet are able to avoid one another’s transmission by persistently changing frequency channels.
Piconet…Features
• A piconet typically has a range of about 30 feet (or 10 meters).
Piconet range varies according to the class of the Bluetooth device. Data transfer rates vary between about 200 and
2100 kilobits per second.
• Because the Bluetooth system hops over 79 channels, the probability of interfering with another Bluetooth system is less than 1.5%. This allows several Bluetooth Piconets to operate in the same area at the same time with minimal interference.
After a Bluetooth device has been added to the temporary network (the Piconet), each device is assigned a specific time period to transmit and
they do not collide or overlap with other units operating within the same Piconet.
• Piconets can be setup to interact with other Piconets to form larger networks called Scatternets. Scatternets allow the master in one Piconet to operate as a slave in another Piconet. While this allows Bluetooth devices in one Piconet to communicate with devices in another Piconet.
Piconet… Safety
• A Bluetooth piconet has encryption and verification built in to the devises upon which it resides.
• There are error-correction schemas and a 4-digit PIN is used on the master device to authenticate the user. However, other devices may not be equipped with a PIN authentication.
Bluetooth Applications
Bluetooth provides support for three general application areas:
• Data and voice access points• Cable replacement• Ad hoc networking
Usage Models
Set of protocols that implement a particular Bluetooth-based application. Some of the highest priority usage models are:
• File transfer• Internet bridge• LAN access• Synchronization• Three-in-one phone• Headset
File Transfer
• one of the most fundamental and useful applications • simple point-to-point links to exchange files and other data
objects• removes the need for cables• much easier to form temporary links between devices to
quickly exchange data• also includes the capability to browse folders on a remote
device.
Internet Bridge
• PC is wirelessly connected to a mobile phone or cordless modem to provide dial-up networking and fax capabilities.
• AT-commands (Attention commands) are needed to control the Mobile phone or modem.
LAN Access
• This usage model enables devices on a piconet to access a LAN. Once connected, a device functions as if it were directly connected (wired) to a LAN.
Synchronization
• It provides a device-to-device (phone, PDA, computer, etc.) synchronization of the PIM (personal information management) information such as phonebook, calendar, message and note information.
• It requires task information to be transferred and processed by devices utilizing a common protocol and format.
Three-in-one Phone
Telephone handsets may connect to three different service providers and act as a:
• Walkie-talkie or handset extension• Cellular phone• Cordless phone connecting to a voice access point
The Ultimate Headset
• Headset is wirelessly connected to act as a remote device’s audio input and output interface
• Increases user’s freedom of movement • Headset must be able to send AT-commands (Attention
commands) and receive result codes
AT Commands
• AT is the abbreviation of Attention• AT commands are instructions used to control and
communicate with a modem• These commands modify modem's behavior or instruct
the modem to do something specific, such as dialing a telephone number
Bluetooth Architecture
• The Bluetooth technology is divided into two specifications: the core and the profile specifications. • The core specification discusses how the technology works• The profile specification focuses on how to build interoperating devices using the core technologies.
Bluetooth Architecture
• RF(radio frequency):The Radio (layer) is the lowest defined layer. It defines the requirements of the Bluetooth transceiver device operating in the 2.4GHz ISM band. Transmits data to and from the Baseband• Baseband: Establishes and manages the physical radio frequency (RF) link between
Bluetooth units that form a piconet.
Bluetooth Architecture
• LMP: Link management protocol responsible for control of radio links.• L2CAP: logical link control and adaptation protocol provides multiplexing,Segmentation.• RFCOMM:radio frequency communication, serial port emulation.• HID: Human interface device for peripheral devices.
Synchronous Connection Oriented(SCO) link
• SCO is a type of communication link that provides for the continuous transfer of data in pre-assigned time periods.
• Point to point full duplex link.• The SCO link reserves slots between the master and the
slave. • Time slot is reserved at every fixed interval.• Used for a circuit switching voice connection.• Needs an asynchronous connectionless (ACL) type link to be
first established.
Asynchronous Connectionless Link
• ACL is a type of communication link that can send data in bursts whenever data is ready to be sent.
• when the communication channel (radio channel) is available (not transmitting another transmission).
• ACL connections can use various types of flow control such as reliable or time bounded.
• This is a packet switched link between a master and slave.• The Bluetooth system has two types of ACL links control
(ACL-C) and user data (ACL-U).
Bluetooth packets
• Bluetooth supports a wide variety of packet types depending on the type of link, throughput and bit fault tolerance.
• Data packets SCO packet –for circuit switching ACL packet –for packet switching• On SCO links packets for low, medium and high quality
voice as well as combined data and voice are supported. • For ACL links 1, 3 and 5 slot packets using medium and
high data rates are supported.
Access code
• The 72-bit access code is mainly used to identify packets transmitted over a Bluetooth channel.
• All data packets sent on the channel share the same access code.
• In addition the access code is used for device paging (finding out if a specific device is in range) and inquiries (used to discover new devices).
Header
• The 18-bit packet header contains the following information
• A 3-bit target device address• A 4-bit type code. Identifies the type of data or control
packet.• A 1-bit fields for flow control, sequencing and packet
acknowledgement.• An 8-bit header error check• To protect the header from transmission errors each bit
is repeated three times in yielding a total length of 54 bits
Forward error correction(FEC)
• FEC is a technique for detecting and correcting errors by adding a small number of extra bits.
• FEC allows optical transmission over longer distances by correcting errors that can happen as the signal-to-noise ratio decreases with distance.
• Within Bluetooth technology, there are 2 versions of this 1/3 FEC and 2/3 FEC.
• 1/3 FEC is a simple 3-times repetition of each info bit.• 2/3 FEC is a shortened Hamming code.
Automatic Repeat Request scheme
• Also referred to as ”backward error correction”.• This is an error control technique in this every block of data
received is checked using the error detection code used, and if the check fails, retransmission of the data is requested this may be done repeatedly, until the data can be verified.
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