Bluetooth - Inglês

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Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras, and video game consoles over a secure, globally unlicensed short-range radio frequency. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group.


Bluetooth is a radio standard and communications protocol primarily designed for low power consumption, with a short range (power-class-dependent: 1 meter, 10 meters, 100 meters) based on low-cost transceiver microchips in each device.

Bluetooth lets these devices communicate with each other when they are in range. The devices use a radio communications system, so they do not have to be in line of sight of each other, and can even be in other rooms, as long as the received transmission is powerful enough.

Class Maximum Permitted Power
Class 1 100 mW (20 dBm) ~100 meters
Class 2 2.5 mW (4 dBm) ~10 meters
Class 3 1 mW (0 dBm) ~1 meter

List of applications

More prevalent applications of Bluetooth include:

  • Wireless control of and communication between a cell phone and a hands-free headset or car kit. This was one of the earliest applications to become popular.
  • Wireless networking between PCs in a confined space and where little bandwidth is required.
  • Wireless communications with PC input and output devices, the most common being the mouse, keyboard and printer.
  • Transfer of files between devices with OBEX.
  • Transfer of contact details, calendar appointments, and reminders between devices with OBEX.
  • Replacement of traditional wired serial communications in test equipment, GPS receivers, medical equipment and traffic control devices.
  • For controls where infrared was traditionally used.
  • Sending small advertisements from Bluetooth enabled advertising hoardings to other, discoverable, Bluetooth devices.
  • Seventh-generation game consoles—Nintendo Wii, Sony PlayStation 3—use Bluetooth for their respective wireless controllers.

Bluetooth vs. Wi-Fi in networking

Bluetooth and Wi-Fi both have their places in today's offices, homes, and on the move: setting up networks, printing, or transferring presentations and files from PDAs to computers.


Bluetooth is implemented in a variety of new products such as phones, printers, modems, and headsets. Bluetooth is acceptable for situations when two or more devices are in proximity to each other and don't require high bandwidth. Bluetooth is most commonly used with phones and hand-held computing devices, either using a Bluetooth headset or transferring files from phones/PDAs to computers.

Bluetooth also simplifies the discovery and setup of services. Bluetooth devices advertise all services they provide. This makes the utility of the service that much more accessible, without the need to worry about network addresses, permissions and all the other considerations that go with typical networks.


Wi-Fi is more analogous to the traditional Ethernet network and requires configuration to set up shared resources, transmit files, set up audio links (for example, headsets and hands-free devices). It uses the same radio frequencies as Bluetooth, but with higher power output resulting in a stronger connection. Wi-Fi is sometimes, but rarely Predefinição:Fact, called "wireless Ethernet." Although this description is inaccurate, it provides an indication of its relative strengths and weaknesses. Wi-Fi requires more setup, but is better suited for operating full-scale networks because it enables a faster connection, better range from the base station, and better security than Bluetooth.Predefinição:Fact

One method for comparing the efficiency of wireless transmission protocols such as Bluetooth and Wi-Fi is spatial capacity, or bits per second per square meter.

Computer requirements

A personal computer must have a Bluetooth dongle in order to be able to communicate with other Bluetooth devices (such as mobile phones, mice and keyboards). While some portable computers and fewer desktop computers already contain an internal Bluetooth dongle, most computers require an external USB Bluetooth dongle. Unlike its predecessor, IrDA, in which each device requires a separate dongle, multiple Bluetooth devices can communicate with a computer over a single dongle.

Operating system support

Linux provides two Bluetooth stacks, with the BlueZ stack included with most Linux kernels. It was originally developed by Qualcomm and Affix. BlueZ supports all core Bluetooth protocols and layers.

Only Microsoft Windows XP Service Pack 2 and later versions of Windows have native support for Bluetooth. Previous versions required the users to install their Bluetooth dongles' own drivers, which tended to clash with the operating system. Microsoft's own Bluetooth dongles (that are packaged with their Bluetooth computer devices) have no external drivers and thus require at least Windows XP Service Pack 2.

Specifications and features

The Bluetooth specification was developed in 1994 by Sven Mattisson and Jaap Haartsen, who were working for Ericsson Mobile Platforms in Lund, Sweden. The specifications were formalized by the Bluetooth Special Interest Group (SIG). The SIG was formally announced on May 20, 1998. Today it has over 7000 companies worldwide. It was established by Ericsson, Sony Ericsson, IBM, Intel, Toshiba, and Nokia, and later joined by many other companies. Bluetooth is also known as IEEE 802.15.1.

Bluetooth 1.0 and 1.0B

Versions 1.0 and 1.0B had many problems, and manufacturers had difficulties making their products interoperable. Versions 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 setback for services planned to be used in Bluetooth environments, such as Consumerium.

Bluetooth 1.1

  • Many errors found in the 1.0B specifications were fixed.
  • Added support for non-encrypted channels.
  • Received Signal Strength Indicator (RSSI).

Bluetooth 1.2

This version is backward-compatible with 1.1 and the major enhancements include the following:

  • Faster Connection and Discovery
  • Adaptive frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence.
  • Higher transmission speeds in practice, up to 721 kbps, as in 1.1.
  • Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets.
  • Host Controller Interface (HCI) support for three-wire UART.

Bluetooth 2.0

This version, specified in November 2004, is backward-compatible with 1.1. The main enhancement is the introduction of an enhanced data rate (EDR) of 3.0 Mbps. This has the following effects:

  • Three times faster transmission speed—up to 10 times in certain cases (up to 2.1 Mbit/s).
  • Lower power consumption through a reduced duty cycle.
  • Simplification of multi-link scenarios due to more available bandwidth.
  • Further improved (bit error rate) performance.

Bluetooth 2.1

Bluetooth Core Specification Version 2.1 + EDR, is fully backward-compatible with 1.1, and will be adopted by the Bluetooth SIG once interoperability testing has completed. This specification includes the following features:

  • Extended inquiry response: provides more information during the inquiry procedure to allow better filtering of devices before connection. This information includes the name of the device, a list of services the device supports, as well as other information like the time of day, and pairing information.
  • Sniff subrating: reduces the power consumption when devices are in the sniff low-power mode, especially on links with asymmetric data flows. Human interface devices (HID) are expected to benefit the most, with mouse and keyboard devices increasing the battery life from 3 to 10 times those currently used.
  • Encryption Pause Resume: enables an encryption key to be refreshed, enabling much stronger encryption for connections that stay up for longer than 24 hours.
  • Secure Simple Pairing: radically improves the pairing experience for Bluetooth devices, while increasing the use and strength of security. It is expected that this feature will significantly increase the use of Bluetooth.

Future of Bluetooth

  • Broadcast Channel: enables Bluetooth information points. This will drive the adoption of Bluetooth into cell phones, and enable advertising models based around users pulling information from the information points, and not based around the intrusive object push model that is used in a limited way today.
  • Topology Management: enables the automatic configuration of the piconet topologies especially in scatternet situations that are becoming more common today. This should all be invisible to the users of the technology, while also making the technology just work.
  • Alternate MAC PHY: enables the use of alternative MAC and PHY's for transporting Bluetooth profile data. The Bluetooth Radio will still be used for device discovery, initial connection and profile configuration, however when lots of data needs to be sent, the high speed alternate MAC PHY's will be used to transport the data. This means that the proven low power connection models of Bluetooth are used when the system is idle, and the low power per bit radios are used when lots of data needs to be sent.
  • QoS improvements: enable audio and video data to be transmitted at a higher quality, especially when best effort traffic is being transmitted in the same piconet.

Bluetooth technology already plays a part in the rising Voice over IP (VOIP) scene, with Bluetooth headsets being used as wireless extensions to the PC audio system. As VOIP becomes more popular, and more suitable for general home or office users than wired phone lines, Bluetooth may be used in cordless handsets, with a base station connected to the Internet link.

The next version of Bluetooth after v2.1, code-named Seattle, that will be called Bluetooth 3.0, has many of the same features, but is most notable for plans to adopt ultra-wideband (UWB) radio technology. This will allow Bluetooth use over UWB radio, enabling very fast data transfers of up to 480 Mbit/s, synchronizations, and file pushes, while building on the very low-power idle modes of Bluetooth. The combination of a radio using little power when no data is transmitted and a high data rate radio to transmit bulk data could be the start of software radios. Bluetooth, given its world-wide regulatory approval, low-power operation, and robust data transmission capabilities, provides an excellent signaling channel to enable the soft radio concept.

On 28 March 2006, the Bluetooth Special Interest Group announced its selection of the WiMedia Alliance Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) version of UWB for integration with current Bluetooth wireless technology.

UWB integration will create a version of Bluetooth wireless technology with a high-speed/high-data-rate option. This new version of Bluetooth technology will meet the high-speed demands of synchronizing and transferring large amounts of data, as well as enabling high-quality video and audio applications for portable devices, multi-media projectors and television sets, and wireless VOIP.

At the same time, Bluetooth technology will continue catering to the needs of very low power applications such as mice, keyboards, and mono headsets, enabling devices to select the most appropriate physical radio for the application requirements, thereby offering the best of both worlds.

The Bluetooth SIG have also announced that they are looking to include Ultra Low Power use cases into Bluetooth, enabling a whole new set of use cases. This inculdes watches displaying Caller ID information, sports sensors monitoring your heart rate during exercise, as well as medical devices. The Medical Devices Working Group is also creating a medical devices profile and associated protocols to enable this market.

Technical information

Communication and connection

A master Bluetooth device can communicate with up to seven devices. This network group of up to eight devices is called a piconet.

A piconet is an ad-hoc computer network, using Bluetooth technology protocols to allow one master device to interconnect with up to seven active devices. Up to 255 further devices can be inactive, or parked, which the master device can bring into active status at any time.

At any given time, data can be transferred between the master and one other device. However, the master switches rapidly from device to another in a round-robin fashion. (Simultaneous transmission from the master to multiple other devices is possible, but not used much.) Either device can switch roles and become the master at any time.

Bluetooth specification allows connecting two or more piconets together to form a scatternet, with some devices acting as a bridge by simultaneously playing the master role and the slave role in one piconet. These devices are planned for 2007.

Setting up connections

Any Bluetooth device will transmit the following sets of information on demand:

  • Device name.
  • Device class.
  • List of services.
  • Technical information, for example, 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 always responds to direct connection requests and transmits the information shown in the list above if requested. Use of device services may require pairing or acceptance by its owner, but the connection itself can be started by any device and held until it goes out of range. Some devices can be connected to only one device at a time, and connecting to them prevents them from connecting to other devices and appearing in inquiries until they disconnect from the other device.

Every device has a unique 48-bit address. However, these addresses are generally not shown in inquiries. Instead, friendly Bluetooth names are used, which can be set by the user. This name appears 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 show only the Bluetooth names and special programs that are required to get additional information about remote devices. This can be confusing as, for example, there could be several phones in range named T610 (see Bluejacking).


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 encryption can, however, be turned off, and passkeys are stored on the device file system, not on the Bluetooth chip itself. Since the Bluetooth address is permanent, a pairing is preserved, even if the Bluetooth name is changed. Pairs can be deleted at any time by either device. Devices generally require pairing or prompt the owner before they allow a remote device to use any or most of their services. Some devices, such as Sony Ericsson phones, usually accept OBEX business cards and notes without any pairing or prompts.

Certain printers and access points allow any device to use its services by default, much like unsecured Wi-Fi networks. Pairing algorithms are sometimes manufacturer-specific for transmitters and receivers used in applications such as music and entertainment.

Air interface

The protocol operates in the license-free ISM band at 2.45 GHz. To avoid interfering with other protocols that 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 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 power 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. Bluetooth is often thought of as wireless USB, whereas Wi-Fi is wireless Ethernet, both operating at much lower bandwidth than the cable systems they are trying to replace. However, this analogy is not entirely accurate since any Bluetooth device can, in theory, host any other Bluetooth device—something that is not universal to USB devices.

Many USB Bluetooth adapters are available, some of which also include an IrDA adapter. Older (pre-2003) Bluetooth adapters, however, have limited services, offering only the Bluetooth Enumerator and a less-powerful Bluetooth Radio incarnation. Such devices can link computers with Bluetooth, but they do not offer much in the way of services that modern adapters do.


Bluetooth implements authentication and key derivation with custom algorithms based on the SAFER+ block cipher. The initialization key and master key are generated with the E22 algorithm. The E0 stream cipher is used for encrypting packets. This makes eavesdropping on Bluetooth-enabled devices more difficult.

Bluetooth was named after a late 900s king, Harald Bluetooth King of Denmark and Norway. He is known for his unification of previously warring tribes from Denmark (including Scania, present-day Sweden, where the Bluetooth technology was invented), and Norway. Bluetooth likewise was intended to unify different technologies, such as computers and mobile phones.

The name may have been inspired less by the historical Harald than the loose interpretation of him in The Long Ships by Frans Gunnar Bengtsson, a Swedish Viking-inspired novel.

The Bluetooth logo merges the Nordic runes analogous to the modern Latin H and B: 10px (haglaz) and 10px (berkanan) forming a bind rune.

Bluetooth Consortium

In 1998, Ericsson, IBM, Intel, and Nokia, formed a consortium and adopted the code name Bluetooth for their proposed open specification. In December 1999, 3Com, Lucent Technologies, Microsoft, and Motorola joined the initial founders as the promoter group. Since that time, Lucent Technologies transferred their membership to their spinoff Agere Systems, and 3Com has left the promoter group.