Bluetooth
What is Bluetooth wireless technology?
Bluetooth technology is how mobile phones, computers, and personal digital assistants (PDAs), not to mention a broad selection of other devices, can be easily interconnected using a short-range wireless connection. Using this technology, users can have all mobile and fixed computer devices be totally coordinated. Bluetooth Basics 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.
Core Specification Versions
- Version 2.0 + Enhanced Data Rate (EDR), adopted November, 2004
- Version 1.2, adopted November, 2003
Specification Make-Up
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.
Spectrum
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.
Interference
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.
Range
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
Power
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.
Data Rate
1 Mbps for Version 1.2; Up to 3 Mbps supported for Version 2.0 + EDR Troubleshooting 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.
Troubleshooting Guide
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.1
- Make sure the devices have Bluetooth functionality switched on.2
- Make sure that the devices you want to communicate with are paired with each other (exceptions exist, for example, when transmitting business cards).3
- Initiate a communication session.4
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.
Making sure profiles match
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.
Bluetooth functionality must be switched on
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."
Pairing
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.
Pairing procedure
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.
Establish connection
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.
Host/guest and multipoint
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.
Cannot pair devices
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.
Most common problems are:
Devices cannot be found
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.
"Pairing unsuccessful" message appears
The pair attempt between two devices failed. Usually this is the case when a wrong pass code or PIN is entered when trying to pair. If you are certain the pass code is correct, try powering down and then powering up both devices.
Pairing succeeded and it still does not work
One of the most common causes for devices not to work together is the fact that two devices do not support the same profile. Unfortunately, support in both ends is a requirement. Usually the answer to this question is to look in the manual where information about profile support can be found. In many devices, like PCs etc., it is also possible to look in the Bluetooth application to find out what profiles (or services) are supported.
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. Bluetooth Wireless Technology Profiles In order to use Bluetooth wireless technology, a device must be able to interpret certain Bluetooth profiles. The profiles define the possible applications. Bluetooth profiles are general behaviors through which Bluetooth enabled devices communicate with other devices. Bluetooth technology defines a wide range of profiles that describe many different types of use cases. By following a guidance provided in Bluetooth specifications, developers can create applications to work with other devices also conforming to the Bluetooth specification.
Advanced Audio Distribution Profile (A2DP)
A2DP describes how stereo quality audio can be streamed from a media source to a sink. The profile defines two roles of an audio source and sink. A typical usage scenario can be considered as the “walkman” class of media player. The audio source would be the music player and the audio sink is the wireless headset. A2DP defines the protocols and procedures that realize distribution of audio content of high-quality in mono or stereo on ACL channels. The term “advanced audio”, therefore, should be distinguished from “Bluetooth audio”, which indicates distribution of narrow band voice on SCO channels as defined in the base band specification.
This profile relies on GAVDP. It includes mandatory support for low complexity sub band codec (SBC) and supports optionally MPEG-1,2 Audio, MPEG-2,4 AAC and ATRAC.
The audio data is compressed in a proper format for efficient use of the limited bandwidth. Surround sound distribution is not included in the scope of this profile.
Audio/Video Remote Control Profile (AVRCP)
AVRCP is designed to provide a standard interface to control TVs, hi-fi equipment, or other to allow a single remote control (or other device) to control all the A/V equipment that a user has access to. It may be used in concert with A2DP or VDP.
AVRCP defines how to control characteristics of streaming media. This includes pausing, stopping and starting playback and volume control as well as other types of remote control operations. The AVRCP defines two roles, that of a controller and target device. The controller is typically considered the remote control device while the target device is the one whose characteristics are being altered. In a “walkman” type media player scenario, the control device may be a headset that allows tracks to be skipped and the target device would be the actual medial player.
This protocol specifies the scope of the AV/C Digital Interface Command Set (AV/C command set, defined by the 1394 trade association) to be applied, realizing simple implementation and easy operability. This protocol adopts the AV/C device model and command format for control messages and those messages are transported by the Audio/Video Control Transport Protocol (AVCTP).
In AVRCP, the controller translates the detected user action to the A/V control signal, and then transmits it to a remote Bluetooth enabled device. The functions available for a conventional infrared remote controller can be realized in this protocol. The remote control described in this protocol is designed specifically for A/V control only.
Hands-Free Profile (HFP)
HFP describes how a gateway device can be used to place and receive calls for a hand-free device. A typical configuration is an automobile using a mobile phone for a gateway device. In the car, the stereo is used for the phone audio and a microphone is installed in the car for sending outgoing audio. HFP is also used for a personal computer to act as a speaker phone for a mobile phone in a home or office environment. HFP uses SCO to carry a mono, PCM audio channel.
Headset Profile (HSP)
The HSP describes how a Bluetooth enabled headset should communicate with a computer or other Bluetooth enabled device such as a mobile phone. When connected and configured, the headset can act as the remote device’s audio input and output interface. The HSP 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.
Object Exchange (OBEX)
OBEX is a transfer protocol that defines data objects and a communication protocol two devices can use to exchange those objects. OBEX is designed to enable devices supporting infrared communication to exchange a wide variety of data and commands in a resource-sensitive standardized fashion. OBEX uses a client-server model and is independent of the transport mechanism and transport API. A Bluetooth enabled device wanting to set up an OBEX communication session with another device is considered to be the client device. The OBEX protocol also defines a folder-listing object, which is used to browse the contents of folders on remote device. RFCOMM is used as the main transport layer for OBEX.
OBEX enables applications to work over the Bluetooth technology protocol stack as well as the IrDA stack. For Bluetooth enabled devices, only connection-oriented OBEX is supported. Three application profiles have been developed using OBEX which include SYNC, FTP and OPP.
Object Push Profile (OPP)
OPP defines the roles of push server and push client. These roles are analogous to and must interoperate with the server and client device roles that GOEP defines. It is called push because the transfers are always instigated by the sender (client), not the receiver (server). OPP focuses on a narrow range of object formats to maximize interoperability. The most common acceptable format is the vCard. OPP may also be used for sending objects such as pictures or appointment details.
Synchronization Profile (SYNC)
The SYNC profile is used in conjunction with GOEP to enable synchronization of calendar and address information (personal information manager (PIM) items) between Bluetooth enabled devices. The profile also describes how an application can support automated synchronization. A common application of this profile is the exchange of data between a PDA and computer. SYNC defines client and server device roles. The profile is also commonly referred to as IrMC synchronization.
