Bluetooth

Bluetooth Basics

Overview of Operation

Troubleshooting

Most common problems are:

Core Specification Versions

Specification Make-Up

Spectrum

Interference

Range

Power

Data Rate

Why Choose Bluetooth wireless technology?

Globally Available

Range of Devices

Ease of Use

Globally Accepted Specification

Secure Connections

How Bluetooth Technology Works

Troubleshooting Guide

Making sure profiles match

Bluetooth functionality must be switched on

Pairing

Pairing procedure

Establish connection

Host/guest and multipoint

Cannot pair devices

Devices cannot be found

"Pairing unsuccessful" message appears

Bluetooth wireless technology is a short-range communications technology intended to replace the cables connecting portable and/or fixed devices while maintaining high levels of security. The key features of Bluetooth technology are robustness, low power, and low cost. The Bluetooth specification defines a uniform structure for a wide range of devices to connect and communicate with each other.

Bluetooth technology has achieved global acceptance such that any Bluetooth enabled device, almost everywhere in the world, can connect to other Bluetooth enabled devices in proximity. Bluetooth enabled electronic devices connect and communicate wirelessly through short-range, ad hoc networks known as piconets. Each device can simultaneously communicate with up to seven other devices within a single piconet. Each device can also belong to several piconets simultaneously. Piconets are established dynamically and automatically as Bluetooth enabled devices enter and leave radio proximity.

A fundamental Bluetooth wireless technology strength is the ability to simultaneously handle both data and voice transmissions. This enables users to enjoy variety of innovative solutions such as a hands-free headset for voice calls, printing and fax capabilities, and synchronizing PDA, laptop, and mobile phone applications to name a few.

Version 2.0 + Enhanced Data Rate (EDR), adopted November, 2004
Version 1.2, adopted November, 2003

Unlike many other wireless standards, the Bluetooth wireless specification gives product developers both link layer and application layer definitions, which supports data and voice applications.

Bluetooth technology operates in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.485 GHz, using a spread spectrum, frequency hopping, full-duplex signal at a nominal rate of 1600 hops/sec. The 2.4 GHz ISM band is available and unlicensed in most countries.

Bluetooth technology’s adaptive frequency hopping (AFH) capability was designed to reduce interference between wireless technologies sharing the 2.4 GHz spectrum. AFH works within the spectrum to take advantage of the available frequency. This is done by detecting other devices in the spectrum and avoiding the frequencies they are using. This adaptive hopping allows for more efficient transmission within the spectrum, providing users with greater performance even if using other technologies along with Bluetooth technology. The signal hops among 79 frequencies at 1 MHz intervals to give a high degree of interference immunity.

The operating range depends on the device class:

Class 3 radios – have a range of up to 1 meter or 3 feet
Class 2 radios – most commonly found in mobile devices – have a range of 10 meters or 30 feet
Class 1 radios – used primarily in industrial use cases – have a range of 100 meters or 300 feet

The most commonly used radio is Class 2 and uses 2.5 mW of power. Bluetooth technology is designed to have very low power consumption. This is reinforced in the specification by allowing radios to be powered down when inactive.

1 Mbps for Version 1.2; Up to 3 Mbps supported for Version 2.0 + EDR

Bluetooth wireless technology is the simple choice for convenient, wire-free, short-range communication between devices. It is a globally available standard that wirelessly connects mobile phones, portable computers, cars, stereo headsets, MP3 players, and more. Thanks to the unique concept of “profiles,” Bluetooth enabled products do not need to install driver software. The technology is now available in its fourth version of the specification and continues to develop, building on its inherent strengths — small-form factor radio, low power, low cost, built-in security, robustness, ease-of-use, and ad hoc networking abilities. Bluetooth wireless technology is the leading and only proven short-range wireless technology on the market today shipping over five million units every week with an installed base of over 500 million units at the end of 2005.

The Bluetooth wireless technology specification is available free-of-charge to our member companies around the globe. Manufacturers from many industries are busy implementing the technology in their products to reduce the clutter of wires, make seamless connections, stream stereo audio, transfer data or carry voice communications. Bluetooth technology operates in the 2.4 GHz, one of the unlicensed industrial, scientific, medical (ISM) radio bands. As such, there is no cost for the use of Bluetooth technology. While you must subscribe to a cellular provider to use GSM or CDMA, with Bluetooth technology there is no cost associated with the use beyond the cost of your device.

Bluetooth technology is available in an unprecedented range of applications from mobile phones to automobiles to medical devices for use by consumers, industrial markets, enterprises, and more. The low power consumption, small size and low cost of the chipset solution enables Bluetooth technology to be used in the tiniest of devices. Have a look at the wide range products made available by our members in the Bluetooth product directory and the component product listing.

Bluetooth technology is an ad hoc technology that requires no fixed infrastructure and is simple to install and set up. You don’t need wires to get connected. The process for a new user is easy – you get a Bluetooth branded product, check the profiles available and connect it to another Bluetooth device with the same profiles. The subsequent PIN code process is as easy as when you identify yourself at the ATM machine. When out-and-about, you carry your personal area network (PAN) with you and can even connect to others.

Bluetooth wireless technology is the most widely supported, versatile, and secure wireless standard on the market today. The globally available qualification program tests member products as to their accordance with the standard. Since the first release of the Bluetooth specification in 1999, over 4000 companies have become members in the Bluetooth Special Interest Group (SIG). Meanwhile, the number of Bluetooth products on the market is multiplying rapidly. Volumes have doubled for the fourth consecutive year and are likely to reach an installed base of 500 million units by the close of 2005.

From the start, Bluetooth technology was designed with security needs in mind. Since it is globally available in the open 2.4 GHz ISM band, robustness was built in from the beginning. With adaptive frequency hopping (AFH), the signal “hops” and thus limits interference from other signals. Further, Bluetooth technology has built-in security such as 128bit encryption and PIN code authentication. When Bluetooth products identify themselves, they use the PIN code the first time they connect. Once connected, always securely connected.

Bluetooth wireless technology is a short-range communications system intended to replace the cables connecting portable and/or fixed electronic devices. The key features of Bluetooth wireless technology are robustness, low power, and low cost. Many features of the core specification are optional, allowing product differentiation.

The Bluetooth core system consists of an RF transceiver, baseband, and protocol stack. The system offers services that enable the connection of devices and the exchange of a variety of data classes between these devices.

The Bluetooth RF (physical layer) operates in the unlicensed ISM band at 2.4GHz. The system employs a frequency hop transceiver to combat interference and fading, and provides many FHSS carriers. RF operation uses a shaped, binary frequency modulation to minimize transceiver complexity. The symbol rate is 1 Megasymbol per second (Msps) supporting the bit rate of 1 Megabit per second (Mbps) or, with Enhanced Data Rate, a gross air bit rate of 2 or 3Mb/s. These modes are known as Basic Rate and Enhanced Data Rate respectively.

During typical operation, a physical radio channel is shared by a group of devices that are synchronized to a common clock and frequency hopping pattern. One device provides the synchronization reference and is known as the master. All other devices are known as slaves. A group of devices synchronized in this fashion form a piconet. This is the fundamental form of communication for Bluetooth wireless technology.

Devices in a piconet use a specific frequency hopping pattern which is algorithmically determined by certain fields in the Bluetooth specification address and clock of the master. The basic hopping pattern is a pseudo-random ordering of the 79 frequencies in the ISM band. The hopping pattern may be adapted to exclude a portion of the frequencies that are used by interfering devices. The adaptive hopping technique improves Bluetooth technology co-existence with static (non-hopping) ISM systems when these are co-located.

The physical channel is sub-divided into time units known as slots. Data is transmitted between Bluetooth enabled devices in packets that are positioned in these slots. When circumstances permit, a number of consecutive slots may be allocated to a single packet. Frequency hopping takes place between the transmission or reception of packets. Bluetooth technology provides the effect of full duplex transmission through the use of a time-division duplex (TDD) scheme.

Above the physical channel there is a layering of links and channels and associated control protocols. The hierarchy of channels and links from the physical channel upwards is physical channel, physical link, logical transport, logical link and L2CAP channel.

Within a physical channel, a physical link is formed between any two devices that transmit packets in either direction between them. In a piconet physical channel there are restrictions on which devices may form a physical link. There is a physical link between each slave and the master. Physical links are not formed directly between the slaves in a piconet.

The physical link is used as a transport for one or more logical links that support unicast synchronous, asynchronous and isochronous traffic, and broadcast traffic. Traffic on logical links is multiplexed onto the physical link by occupying slots assigned by a scheduling function in the resource manager.

A control protocol for the baseband and physical layers is carried over logical links in addition to user data. This is the link manager protocol (LMP). Devices that are active in a piconet have a default asynchronous connection-oriented logical transport that is used to transport the LMP protocol signaling. For historical reasons this is known as the ACL logical transport. The default ACL logical transport is the one that is created whenever a device joins a piconet. Additional logical transports may be created to transport synchronous data streams when this is required.

The link manager function uses LMP to control the operation of devices in the piconet and provide services to manage the lower architectural layers (radio layer and baseband layer). The LMP protocol is only carried on the default ACL logical transport and the default broadcast logical transport.

Above the baseband layer the L2CAP layer provides a channel-based abstraction to applications and services. It carries out segmentation and reassembly of application data and multiplexing and de-multiplexing of multiple channels over a shared logical link. L2CAP has a protocol control channel that is carried over the default ACL logical transport. Application data submitted to the L2CAP protocol may be carried on any logical link that supports the L2CAP protocol.

The Bluetooth Special Interest Group (SIG) is a trade association and as such, we do not make, manufacture, or sell products. Our member companies build Bluetooth wireless technology into products using a specification, or technology map, which helps us ensure their products provide specific Bluetooth applications to the end user. Because we, the Bluetooth SIG, have over 4000 member companies - all of which are implementing the technology in products varying from USB adapters to cars to medical devices - it is virtually impossible for us to give technical support. The following is a general troubleshooting guide that should help you to identify what problems you are experiencing. For product specific assistance, you will need to contact the manufacturer of your product(s) directly.

It is important to start by noting that Bluetooth wireless technology is a wireless standard and specification that product manufacturers build into their products. The manufacturer who produces the Bluetooth enabled product does so in compliance with an industry standard but integrates the technology into its product in its unique way. Therefore, for technical support for Bluetooth enabled products, consumers should ultimately rely on the product manufacturer.

There are a few things you need to think about to get Bluetooth devices to work together. The most obvious being, of course, that you will need Bluetooth wireless functionality in all devices you want to connect. If you are not sure whether your devices contain Bluetooth technology, you will need to contact the manufacturers of the devices or check the products’ technical specifications.

Make sure that the corresponding Bluetooth profile exists in both devices.
Make sure the devices have Bluetooth functionality switched on.
Make sure that the devices you want to communicate with are paired with each other (exceptions exist, for example, when transmitting business cards).
Initiate a communication session.

Have you done everything right and it still doesn't work? Below you will find some general tips of how to deal with potential problems in regard to Bluetooth connectivity and how to easily establish Bluetooth connections.

For devices to work together it is important that each device that communicates share the same profile. Some examples:

If you want to connect a headset to a mobile phone you will need the Hands-Free Profile (HFP) in both devices.
If you want to establish a dial-up session to reach the Internet from a PDA connected to a mobile phone, you would need the Dial-Up Networking (DUN) Profile in both devices.
If you want to print from a mobile phone to a printer, both devices typically will need the Basic Printing Profile (BPP). These are just some examples, but when purchasing devices you need to keep this concept in mind to make sure that they will work together as expected. Usually you will find information about what profiles are supported in the user manual.

An example that is not likely to work together:

A mouse, which typically supports the Human Interface Device (HID) Profile, and a camera are unlikely to work together since presently no cameras support the HID profile.

For devices to communicate using Bluetooth wireless technology you will need to make sure that both devices have the Bluetooth functionality turned on. Even though the basic design of Bluetooth provides for extremely low power consumption, the functionality can be switched off to save even more power, or to disable radio functionality in special situations such as during airplane take off. In most devices the Bluetooth functionality (radio) is switched on by software. This is typically done from a menu choice, "Turn Bluetooth radio on."

Normally, for security reasons, two Bluetooth devices always need to be initially paired before they can exchange data. The term, pairing (or bonding as it is sometimes referred to), normally means that two devices are exchanging protected passkeys. Once paired, all information sent over the Bluetooth link is encrypted and will only be able to reach devices that are authorized to do so by the pairing process. In certain instances it may not be necessary to conduct the pairing procedure. For example, when exchanging business cards between two mobile phones it may be too cumbersome to pair with a password. Usually there is a setting in the device, for such cases, in which you can set a lower level of security.

Typically a pairing is done in two ways, depending on the type of devices. For example, pairing a headset and a mobile phone necessitates setting one of the devices into pairing mode and activating the pairing from the other device.

Headset is set into pairing mode, typically by specific sequence of button pushing.
In the mobile phone, the pairing is initiated by activating this function from the appropriate menu.

With many devices, especially those that have built-in Bluetooth functionality, there is no need to perform additional operations to establish a connection once paired. Typically, a mobile phone will automatically connect to the headset when a call is initiated. If at any time a pairing or connection between two devices needs to be re-established, the pairing should be conducted in a private, secure location.

For each small personal network (piconet) of between two and seven devices, one device always acts as host and the other units are guests. All devices, independent of capability, can take both host and guest roles. If you have many devices connected in a personal network (more than one guest to a host) it is called multipoint. A computer, for example, could simultaneously connect and transmit data to a PDA, a camera, and a mobile phone at the same time. However, some devices, like wireless headsets, cannot maintain more than one simultaneous connection.

In general, pairing between devices is not a problem; however, you will need to know how to initiate and facilitate the initial pairing, which is described briefly above and for greater detail see Connecting Devices.

Bluetooth is off or the other device is not in "discoverable mode". Make the unit you are trying to find and pair with visible/discoverable by either turning this on from the appropriate menu or by a sequence of keystrokes usually on devices with limited user interface. When you are done pairing, you can turn the device back to non-discoverable if you have security concerns.

Dec 2008

The pair attempt between two devices failed. Usually this is the case when a wrong passcode or PIN is entered when trying to pair. If you are certain the passcode is correct, try powering down and then powering up both devices.

Another common cause is, of course, that it is difficult to find the right commands or menus for making connections. This is more difficult to answer since it depends very much on the manufacturer implementation and the user interface of the device. The only recommendation we can provide is to look in the user documentation and/or to contact the device manufacturer's support department.