Bluetooth

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.

Introduction

Bluetooth is a wirefree Radio standard primarily designed for low power consumption, with a short range (power class depended 10 centimetres, 10 metres, 100 metres or up to 400 metres [https://www.bluetooth.org/admin/bluetooth2/faq/view_record.php?id=49], ) and with a low-cost Transceiver Microchip in each device.

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 (328 feet) of each other, dependent on the power class of the product. Products are available in one of three power classes:

1. Class 1 (100 mW) [still readily available]: It has the longest range at up to 100 metres (320 ft).
2. Class 2 (2.5 mW) [most common]: It allows a quoted transmission distance of 10 metres (32 ft).
3. Class 3 (1 mW) [rare]: It allows transmission of 10 cm (3.9 in), with a maximum of 1 metre (3.2 ft).

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
• Bluetooth cell phones have been sold in large numbers, and are able to connect to computers, Personal digital assistants (PDAs) and, specifically, to Handsfree devices. The standard also includes support for more powerful, longer-range devices suitable for constructing wireless LANs.
• Transfer of files (images, mp3s, etc) between mobile phones, Personal digital assistants (PDAs) and computers via OBEX
• Certain mp3 players and Digital Cameras to transfer files to and from computers
• Bluetooth headsets for mobile phones & Smartphones
• Some testing equipment is bluetooth enabled
• Medical applications - Advanced Medical Electronics Corporation is working on several devices
• Certain GPS receivers transfer NMEA data via Bluetooth
• Bluetooth car kits - Acura was the first motor vehicle manufacturer to install handsfree Bluetooth technology in the 2004 Acura TL. Later on BMW added 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. Companies like Parrot manufacture Bluetooth hands-free car kits for well-known brand car manufacturers.
• Certain data logging equipment transmits data to a computer via Bluetooth.
• For remote controls where infrared was traditionally used.

Specifications and Features

Bluetooth 1.0 and 1.0B

Bluetooth 1.1

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

Bluetooth 1.2

• Adaptive Frequency Hopping (AFH), which improves resistance to Radio frequency 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

• 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.

Technical information

Communication & Connection

At any given time, data can be transferred between the master and 1 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). Either device may switch the master/slave role at any time.

Bluetooth specification allows connecting 2 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 2 years (2007).

Setting up connections

• Device Name
• Device Class
• List of services
• Technical information eg: device features, manufacturer, Bluetooth specification, clock offset

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 to direct connection requests and will transmit the information shown in the list above if requested for it. Use of the device's services however may require pairing or its owner to accept but the connection itself can be started by any device and be held until it goes out of range. Some devices can only be connected to one device at a time and connecting to them will prevent them from connecting to other devices and showing up in inquiries until they disconnect the other device.

Every device has a unique 48-bit address. However these addresses are generally not shown in inquiries and instead friendly "Bluetooth names" are used which can be set by the user, and will appear when another user scans for devices and in lists of paired devices. Most phones have the Bluetooth name set to the manufacturer and model of the phone by default. Most phones and laptops will only show the Bluetooth names and special programs are required to get additional information about remote devices. This can get confusing with activities such as Bluejacking as there could be several phones in range named "T610" for example. On Nokia phones the Bluetooth 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 ("hci0" may need to be replaced by another device name).

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

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), which will also be transmitted when other devices perform an inquiry. On some phones this information is translated into a little icon displayed beside the device's name.

Bluetooth devices will also transmit a list of services if requested by another device; this also includes some extra information such as the name of the service and what channel it is on. These channels are virtual and have nothing to do with the frequency of the transmission, much like TCP ports. A device can therefore have multiple identical services.

        Browsing 00:0E:ED:B0:AF:34 ...
        Service Name: OBEX Object Push
        Service RecHandle: 0x10000
        Service Class ID List:
         "OBEX Object Push" (0x1105)
        Protocol Descriptor List:
         "L2CAP" (0x0100)
         "RFCOMM" (0x0003)
        Channel: 9
         "OBEX" (0x0008)
        Language Base Attr List:
         code_ISO639: 0x454e
         encoding:    0x6a
         base_offset: 0x100
        Profile Descriptor List:
         "OBEX Object Push" (0x1105)
         Version: 0x0100

Technical data used for managing the connection may also be extracted from a device.

        BD Address:  00:11:24:B3:50:FB
        Device Name: My little special laptop
        LMP Version: 2.0 (0x3) LMP Subversion: 0x7ad
        Manufacturer: Cambridge Silicon Radio (10)
        Features: 0xff 0xff 0x8f 0xfe 0x9b 0xf9 0x00 0x80
                <3-slot packets> <5-slot packets> <encryption> <slot offset>
                <timing accuracy> <role switch> <hold mode> <sniff mode>
                <park state> <RSSI> <channel quality> <SCO link> <HV2 packets>
                <HV3 packets> <A-law log> <CVSD> <paging scheme>
                <power control> <transparent SCO> <broadcast encrypt>
                <EDR ACL 2 Mbps> <EDR ACL 3 Mbps> <enhanced iscan>
                <interlaced iscan> <interlaced pscan> <inquiry with RSSI>
                <extended SCO> <EV4 packets> <EV5 packets> <AFH cap. slave>
                <AFH class. slave> <3-slot EDR ACL> <5-slot EDR ACL>
                <AFH cap. master> <AFH class. master> <EDR eSCO 2 Mbps>
                <EDR eSCO 3 Mbps> <3-slot EDR eSCO> <extended features>

Pairing

Air interface

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, both operating at much lower bandwidth than the cable systems they are trying to replace.

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

Embedded Bluetooth

Security concerns

In November 2003, Ben and Adam Laurie from A.L. Digital Ltd. discovered that serious flaws in Bluetooth security may lead to disclosure of personal data (see ). 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 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 was used for this experiment.

2004:

In April 2004, security consultants @Stake 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 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.

Note: the virus was written as a proof-of-concept by a group of virus writers known as 29a and sent to anti-virus groups. Thus it should be regarded as a potential (but NOT real) security threat of Bluetooth or Symbian OS as the virus has never spread in the wild.

In August 2004, a world-record-setting experiment (see also Bluetooth sniping) showed that the range of class 2 Bluetooth radios could be extended to 1.78 km (1.08 Mile) with directional antennas. This poses a potential security threat as it enables attackers to access vulnerable Bluetooth-devices from a distance beyond expectation. However such experiments will not work using signal amplifiers as the attacker must also be able to receive information from its victim in order to set up a connection. No attack can be made against a bluetooth device unless the attacker knows its Bluetooth address and which channels to transmit on.

2005:

In June 2005 Yaniv Shaked and Avishai Wool published the paper "Cracking the Bluetooth PIN1", 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 PIN 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.

In August 2005, police in Cambridgeshire, England, issued warnings about thieves using Bluetooth-enabled phones to track other devices left in cars. Police are advising users to ensure any mobile networking connections are de-activated if laptops and other devices are left in this way. However the best way is to not leave any valuable devices in cars. They should be kept with you.

Security measures

Bluetooth profiles

Advanced Audio Distribution Profile (A2DP)

Also referred to as the AV profile, it is designed to transfer a stereo 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 on Layer 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 are 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.

Future of Bluetooth

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.

Bluetooth may also be used for remote sales technology, allowing wireless access to vending machines and other commercial enterprises.

Origin of the name and the logo

In 1998, Intel, IBM, Ericsson, Nokia and Toshiba formed the consortium among themselves and adopted the code name Bluetooth for their proposed open specification. Later Microsoft, 3Com and Lucent Technologies joined the the initial founders as the promoter group. Since that time, Lucent Technologies transferred their membership to their spinoff Agere Systems and 3Com has since left the Promoter group.

Of the original Promoter group, only Intel has not yet shipped a Bluetooth enabled product.

See also

• Bluechat
• Bluejacking - a form of communication via Bluetooth
• Bluetooth sniping
• Bluesnarfing
• Blunt - Bluetooth protocol stack for Newton OS 2.1
• Cable spaghetti - a problem wireless technology hopes to solve
• Origine of the word
• INSTEON - an alternative digital radio and powerline technology that claims to be simpler and cheaper than Bluetooth.
• IrDA
• OBEX
• Jini
• LibertyLink
• MaxStream
• OSGi Alliance
• Salutation
• Service Location Protocol
• Toothing
• Ultra wideband
• Universal plug-and-play
• UWB Forum - partner trade assocation for higher speed "Bluetooth" built with Ultra-Wideband.
• Wi-Fi
• Wireless dating