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Bluetooth

From Academic Kids

Bluetooth logo
This article is about the Bluetooth wireless specification. For King Harold Bluetooth, see Harold I of Denmark

Bluetooth is an industrial specification for wireless personal area networks (PANs).

Bluetooth provides a way to connect and exchange information between devices like personal digital assistants (PDAs), mobile phones, laptops, PCs, printers and digital cameras via a secure, low-cost, globally available short range radio frequency.

Bluetooth lets these devices talk to each other when they come in range, even if they are not in the same room, as long as they are within up to 100 metres (320 feet) of each other, dependent on the power class of the product. Products are available in one of three power classes:

  • Class 3 (1 mW) is most common and allows a quoted transmission distance of 10 metres (32 feet)
  • Class 2 (2.5mW) is the rarest and allows transmission of 20 metres (64 feet)
  • Class 1 (100mW) has the longest range at up to 100 metres. This class of product is readily available.

The specification was first developed by Ericsson, and was later formalized by the Bluetooth Special Interest Group (SIG). The SIG was formally announced on May 20, 1999. It was established by Sony Ericsson, IBM, Intel, Toshiba and Nokia, and later joined by many other companies as Associate or Adopter members.

Contents

About the name

The system is named after a Danish king Harald Bltand (Harold Bluetooth in English), King of Denmark and Norway from 935 and 936 respectively, to 940 known for his unification of previously warring tribes from Denmark, Norway and Sweden. Bluetooth likewise was intended to unify different technologies like computers and mobile phones. The Bluetooth logo merges the Nordic runes for H and B. This is the official story: however, the actual Harald Bltand that was referred to in naming Bluetooth was most probably the liberal interpretation given to him in The Long Ships by Frans Gunnar Bengtsson, a Swedish best-selling Viking-inspired novel.

General information

A typical Bluetooth
Enlarge
A typical Bluetooth mobile phone headset

The latest version currently available to consumers is 2.0, but few manufacturers have started shipping any products yet. Apple Computer, Inc. offered the first products supporting version 2.0 to end customers in January 2005. The core chips have been available to OEMs (from November 2004), so there will be an influx of 2.0 devices in mid-2005. The previous version, on which all earlier commercial devices are based, is called 1.2.

Bluetooth is a wireless radio standard primarily designed for low power consumption, with a short range (up to 10 meters [1] (https://www.bluetooth.org/admin/bluetooth2/faq/view_record.php?id=49), ) and with a low-cost transceiver microchip in each device.

Cell phones with integrated Bluetooth technology have also been sold in large numbers, and are able to connect to computers, PDAs and, specifically, to handsfree devices. BMW was the first motor vehicle manufacturer to install handsfree Bluetooth technology in its cars, adding it as an option on its 3 Series, 5 Series, 7 Series and X5 vehicles. Since then, other manufacturers have followed suit, with many vehicles, including the 2004 Toyota Prius and the 2004 Lexus LS 430. The Bluetooth car kits allow users with Bluetooth-equipped cell phones to make use of some of the phone's features, such as making calls, while the phone itself can be left in a suitcase or in the boot/trunk, for instance.

The standard also includes support for more powerful, longer-range devices suitable for constructing wireless LANs.

Bluetooth applications

  • Wireless Networking between desktops and laptops, or desktops in a confined space and where little bandwidth is required
  • Bluetooth peripherals such as printers, mice and keyboards
  • Transfer of files (images, mp3s, etc) between mobile phones, PDA's and computers via OBEX
  • Certain low-end mp3 players and Digital Cameras to transfer files to and from computers
  • Car kits & Bluetooth headsets for mobile phones
  • Medical applications - Advanced Medical Electronics Corporation is working on several devices
  • Certain GPS receivers transfer NMEA data via Bluetooth

Technical information

A Bluetooth device playing the role of "master" can communicate with up to 7 devices playing the role of "slave". At any given time, data can be transferred between the master and one slave; but the master switches rapidly from slave to slave in a round-robin fashion. (Simultaneous transmission from the master to multiple slaves is possible, but not used much in practice). These groups of up to 8 devices (1 master and 7 slaves) are called piconets.

The Bluetooth specification also allows connecting two or more piconets together to form a scatternet, with some devices acting as a bridge by simultaneously playing the master role in one piconet and the slave role in another piconet. These devices have yet to come, though are supposed to appear within the next two years.

Any device may perform an "inquiry" to find other devices to which to connect, and any device can be configured to respond to such inquiries. However if the device trying to connect knows the address of the device it will always respond.

Every device has a unique 48-bit address, on Nokia phones this address may be found by entering "*#2820#". On computers running Linux the address and class of a USB Bluetooth dongle may be found by entering "hciconfig hci0 class" as root (not every device will be called "hci0") . Every device also has a 24-bit class identifier. This provides information on what kind of a device it is (Phone, Smartphone, Computer, Headset, etc), this will also be transmitted when other devices perform an inquiry.

       BD Address: 00:10:60:A7:93:19 ACL MTU: 192:8 SCO MTU: 64:8
       Class: 0x020005
       Service Classes: Networking
       Device Class: Miscellaneous,

Devices also have friendly "Bluetooth names" which can be set by the user, and will appear when another user scans for devices, and in lists of paired devices. However since the Bluetooth address is permanent a pairing will be preserved even if the Bluetooth name is changed. Most phones have the Bluetooth name set to the manufacturer and model of the phone.

Pairs of devices may establish a trusted relationship by learning (by user input) a shared secret known as a "passkey". A device that wants to communicate only with a trusted device can cryptographically authenticate the identity of the other device. Trusted devices may also encrypt the data that they exchange over the air so that no one can listen in.

The protocol operates in the license-free ISM band at 2.45 GHz. In order to avoid interfering with other protocols which use the 2.45 GHz band, the Bluetooth protocol divides the band into 79 channels (each 1 MHz wide) and changes channels up to 1600 times per second. Implementations with versions 1.1 and 1.2 reach speeds of 723.1 kbit/s. Version 2.0 implementations feature Bluetooth Enhanced Data Rate (EDR), and thus reach 2.1 Mbit/s. Technically version 2.0 devices have a higher power consumption, but the three times faster rate reduces the transmission times, effectively reducing consumption to half that of 1.x devices (assuming equal traffic load).

Bluetooth differs from Wi-Fi in that the latter provides higher throughput and covers greater distances but requires more expensive hardware and higher power consumption. They use the same frequency range, but employ different multiplexing schemes. While Bluetooth is a cable replacement for a variety of applications, Wi-Fi is a cable replacement only for local area network access. A glib summary is that Bluetooth is wireless USB whereas Wi-Fi is wireless Ethernet.

Many USB Bluetooth adapters are available, some of which also include an IrDA adapter.

Embedded Bluetooth

Bluetooth devices and modules are increasingly being made available which come with an embedded stack and a standard UART port. The UART protocol can be as simple as the industry standard AT protocol, which allows the device to be configured to cable replacement mode. This means it now only takes a matter of hours (instead of weeks) to enable legacy wireless products that communicate via UART port.

Features by version

Bluetooth 1.0 and 1.0B

Versions 1.0 and 1.0B had numerous problems and the various manufacturers had great difficulties in making their products interoperable. 1.0 and 1.0B also had mandatory Bluetooth Hardware Device Address (BD_ADDR) transmission in the handshaking process, rendering anonymity impossible at a protocol level, which was a major set back for services planned to be used in Bluetooth environments, such as Consumerium.

Bluetooth 1.1

In version 1.1 many errata found in the 1.0B specifications were fixed. There was added support for non-encrypted channels.

Bluetooth 1.2

This version is backwards compatible with 1.1 and the major enhancements include

  • Adaptive Frequency Hopping (AFH), which improves resistance to radio interference by avoiding using crowded frequencies in the hopping sequence
  • Higher transmission speeds in practice
  • extended Synchronous Connections (eSCO), which improves voice quality of audio links by allowing retransmissions of corrupted packets.
  • Received Signal Strength Indicator (RSSI)
  • Host Controller Interface (HCI) support for 3-wire UART
  • HCI access to timing information for Bluetooth applications.

Bluetooth 2.0

This version is backwards compatible with 1.x. The main enhancement is the introduction of Enhanced Data Rate (EDR) of 2.1 Mbit/s. This has the following effects (Bluetooth SIG, 2004):

  • 3 times faster transmission speed (up to 10 times in certain cases).
  • Lower power consumption through reduced duty cycle.
  • Simplification of multi-link scenarios due to more available bandwidth.
  • Further improved BER (Bit Error Rate) performance.

Future Bluetooth uses

One of the ways Bluetooth technology may become useful is in Voice over IP. When VOIP becomes more widespread, companies may find it unnecessary to employ telephones physically similar to today's analogue telephone hardware. Bluetooth may then end up being used for communication between a cordless phone and a computer listening for VOIP and with an infrared PCI card acting as a base for the cordless phone. The cordless phone would then just require a cradle for charging. Bluetooth would naturally be used here to allow the cordless phone to remain operational for a reasonably long period. In May 2005, the Bluetooth Special Interest Group (SIG) announced its intent to work with UWB manufacturers to develop a next-generation Bluetooth technology using UWB technology and delivering UWB speeds. This will enable Bluetooth technology to be used to deliver high speed network data exchange rates required for wireless VOIP, music and video applications.

Security concerns

In November 2003, Ben and Adam Laurie from A.L. Digital Ltd. (http://www.thebunker.net/index.html) discovered that serious flaws in Bluetooth security lead to disclosure of personal data (see http://bluestumbler.org). It should be noted however that the reported security problems concerned some poor implementations of Bluetooth, rather than the protocol itself.

In a subsequent experiment, Martin Herfurt from the trifinite.group (http://trifinite.org/trifinite_group.html) was able to do a field-trial at the CeBIT fairgrounds showing the importance of the problem to the world. A new attack called BlueBug (http://trifinite.org/trifinite_stuff_bluebug.html) was used for this experiment.

In April 2004, security consultants @Stake (http://www.atstake.com) revealed a security flaw that makes it possible to crack into conversations on Bluetooth based wireless headsets by reverse engineering the PIN.

This is one of a number of concerns that have been raised over the security of Bluetooth communications. In 2004 the first purported virus using Bluetooth to spread itself among mobile phones appeared (http://www.theregister.co.uk/2004/06/15/symbian_virus/) for the Symbian OS. The virus was first described by Kaspersky Labs and requires users to confirm the installation of unknown software before it can propagate. The virus was written as a proof-of-concept by a group of virus writers known as 29a and sent to anti-virus groups. Because of this, it should not be regarded as a security failure of either Bluetooth or the Symbian OS. It has not propagated 'in the wild'.

In August 2004, a world-record-setting experiment (http://trifinite.org/trifinite_stuff_lds.html) (see also Bluetooth sniping) showed that with directional antennas the range of class 2 Bluetooth radios could be extended to one mile. This enables attackers to access vulnerable Bluetooth-devices from a distance beyond expectation.

In June 2005 Yaniv Shaked and Avishai Wool published the paper "Cracking the Bluetooth PIN1" (http://www.eng.tau.ac.il/~yash/shaked-wool-mobisys05/index.html), which shows both passive and active methods for obtaining the PIN for a Bluetooth Link. The passive attack would allow a suitably equipped attacker to eavesdrop on communications and spoof if they were present at the time of initial pairing. The active method makes use of a specially constructed message that must be inserted at a specific point in the protocol, to make the master and slave repeat the pairing process. After that the first method may be used to crack the PIN. This attack's major weakness is that it requires the user of the devices under attack to re-enter their PIN1 during the attack when their device prompts them to. Also, this active attack will, most likely require custom hardware, as most commercially available Bluetooth Devices are not capable of the timing necessary.

Bluetooth uses the SAFER+ algorithm for authentication and key generation.

Bluetooth profiles

In order to use Bluetooth, a device must be able to interpret certain Bluetooth profiles. These define the possible applications. The following profiles are defined and adopted by the Bluetooth SIG:

Advanced Audio Distribution Profile (A2DP) 
It is designed to transfer an audio stream like music from an MP3 player to a headset or car radio. This profile relies on GAVDP. It includes mandatory support for low complexity subband codec (SBC) and supports optionally: MPEG-1,2 Audio, MPEG-2,4 AAC and ATRAC. Bluetake's I-Phono Hi-Fi Sport Headphones are an example of this profile being employed.
Audio/Video Remote Control Profile (AVRCP) 
This profile is designed to provide a standard interface to control TVs, Hi-fi equipment, etc. to allow a single remote control (or other device) to control all of the A/V equipment that a user has access to. It may be used in concert with A2DP or VDP.
Basic Imaging Profile (BIP) 
This profile is designed for sending images between devices and includes the ability to resize, and convert images to make them suitable for the receiving device. It may be broken down into smaller pieces:
Image Push 
Allows the sending of images from a device the user controls.
Image Pull 
Allows the browsing and retrieval of images from a remote device.
Advanced Image Printing 
print images with advanced options using the DPOF format developed by Canon, Kodak, Fuji, and Matsushita
Automatic Archive 
Allows the automatic backup of all the new images from a target device. For example, a laptop could download all of the new pictures from a camera whenever it is within range.
Remote Camera 
Allows the initiator to remotely use a digital camera. For example, a user could place a camera on a tripod for a group photo, use their phone handset to check that everyone is in frame, and activate the shutter with the user in the photo.
Remote Display 
Allows the initiator to push images to be displayed on another device. For example, a user could give a presentation by sending the slides to a digital projector.
Basic Printing Profile (BPP) 
This allows devices to send text, e-mails, vCards, or other items to printers based on print jobs. It differs from HCRP in that it needs no printer-specific drivers. This makes it more suitable for embedded devices such as mobile phones and digital cameras which cannot easily be updated with drivers dependent upon printer vendors.
Common ISDN Access Profile (CIP) 
This provides unrestricted access to the services, data and signalling that ISDN offers.
Cordless Telephony Profile (CTP) 
This is designed for cordless phones to work using Bluetooth. It is hoped that mobile phones could use a Bluetooth CTP gateway connected to a landline when within the home, and the mobile phone network when out of range. It is central to the Bluetooth SIG's '3-in-1 phone' use case.
Dial-up Networking Profile (DUN) 
This profile provides a standard to access the Internet and other dial-up services over Bluetooth. The most common scenario is accessing the Internet from a laptop by dialling up on a mobile phone, wirelessly. It is based on SPP, and provides for relatively easy conversion of existing products, through the many features that it has in common with the existing wired serial protocols for the same task. These include the AT command set specified in ETSI 07.07, and PPP.
Fax Profile (FAX) 
This profile is intended to provide a well defined interface between a mobile phone or fixed-line phone and a PC with Fax software installed. Support must be provided for ITU T.31 and / or ITU T.32 AT command sets as defined by ITU-T. Data and voice calls are not covered by this profile.
File Transfer Profile (FTP) 
Provides access to the file system on another device. This includes support for getting folder listings, changing to different folders, getting files, putting files and deleting files. It uses OBEX as a transport and is based on GOEP.
General Audio/Video Distribution Profile (GAVDP) 
Provides the basis for A2DP, and VDP.
Generic Access Profile (GAP) 
Provides the basis for all other profiles.
Generic Object Exchange Profile (GOEP) 
provides a basis for other data transfer profiles. Based on OBEX.
Hands Free Profile (HFP) 
This is commonly used to allow car hands free kits to communicate with mobile phones in the car. It uses SCO to carry a mono, PCM audio channel. It is considered to be the killer app for Bluetooth as more Governments are passing legislation to ban the direct use of mobile phones while driving.
Hard Copy Cable Replacement Profile (HCRP) 
This provides a simple wireless alternative to a cable connection between a device and a printer. Unfortunately it does not set a standard regarding the actual communications to the printer, so drivers are required specific to the printer model or range. This makes this profile less useful for embedded devices such as digital cameras and palmtops, as updating drivers can be problematic.
Headset Profile (HSP) 
This is the most commonly used profile, providing support for the popular Bluetooth Headsets to be used with mobile phones. It relies on SCO for audio and a subset of AT commands from GSM 07.07 for minimal controls including the ability to ring, answer a call, hang up and adjust the volume.
Human Interface Device Profile (HID) 
provides support for devices such as mice, joysticks, keyboards, etc. It is designed to provide a low latency link, with low power requirements. Popular devices that feature support for this profile include: Logitech diNovo Media Desktop 2.0, Microsoft Optical Desktop Elite. The unreleased PlayStation 3 controllers will also use BT HID.
Intercom Profile (ICP) 
This is often referred to as the walkie-talkie profile. It is another TCS based profile, relying on SCO to carry the audio. It is proposed to allow voice calls between two Bluetooth capable handsets, over Bluetooth.
Object Push Profile (OPP) 
A basic profile for sending "objects" such as pictures, virtual business cards, or appointment details. It is called push because the transfers are always instigated by the sender (client), not the receiver (server).
Personal Area Networking Profile (PAN) 
This profile is intended to allow the use of Bluetooth Network Encapsulation Protocol onLayer 3 protocols for transport over a Bluetooth link.
Serial Port Profile (SPP) 
This profile is based on the ETSI TS07.10 specification and uses the RFCOMM protocol. It emulates a serial cable to provide a simply implemented wireless replacement for existing RS232 based serial communications applications, including familiar control signals. It provides the basis for DUN, FAX, HSP and LAN profiles.
Service Discovery Application Profile (SDAP) 
This mandatory profile is used to find out which profiles are offered by the Server device.
SIM Access Profile (SAP) 
This allows devices such as car phones with built in GSM transceivers to connect to a SIM card in a phone with Bluetooth, so the car phone itself doesn't require a separate SIM card.
Synchronisation Profile (SYNCH) 
This profile allows synchronisation of Personal Information Manager (PIM) items. As this profile originated as part of the infrared specifications but has been adopted by the Bluetooth SIG to form part of the main Bluetooth specification, it is also commonly referred to as IrMC Synchronization.
Video Distribution Profile (VDP) 
This profile allows the transport of a video stream. It could be used for streaming a recorded video from a PC media centre to a portable player, or from a digital video camera to a TV. Support for H.263 baseline is mandatory. Support for MPEG-4 Visual Simple Profile, H.263 profiles 3 and 8 re optionally supported, and covered in the specification.

The remaining profiles are still not finalised, but are currently proposed within the Bluetooth SIG:

  • Handsfree Profile 1.5 (HFP 1.5)
  • Unrestricted Digital Information (UDI)
  • Wireless application Protocol over BT (WAP)
  • Extended Service discovery profile (ESDP)
  • Local Positioning Profile (LPP)
  • Video Conferencing Profile (VCP)
  • Device ID (DID) : Allows a device to be identified according to the Specification version met, the Manufacturer, product, product version, etc. It enables similar applications to those the Plug-and-play specification allows.

Compatibility of products with profiles can be verified on the Bluetooth Qualification website (http://qualweb.bluetooth.org/Template2.cfm?LinkQualified=QualifiedProducts).

See also

References

External links

da:Bluetooth de:Bluetooth es:Bluetooth fa:بلوتوث fr:Bluetooth ko:블루투스 it:Bluetooth he:שן כחולה nl:Bluetooth ja:Bluetooth no:Bltann pl:Bluetooth pt:Bluetooth ru:Bluetooth fi:Bluetooth sv:Bluetooth zh:蓝牙

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