Bluetooth Glossary

Active mode - In the active mode, a Bluetooth device actively participates in the channel. The master checks the traffic demands to and from the slaves and schedules transmissions accordingly. It supervises synchronization to keep the slaves synchronized to the channel as well.

Authentication - This is the process of verifying the device at the other end of the link. The Bluetooth device checks to make sure that the other device has an ID to which it has been previously paired or a link key to which it is authorized access.

BER - Bit Error Rate. A measure of the quality of the wireless link by noting the number of errors that have been noted and corrected.

Bluetooth - An open specification for wireless communication of data and voice. The specification uses a short-range radio link created on an ad hoc basis between electronic devices.

Channel sequence - Sometimes called "channel hopping sequence." This is the sequence that a Bluetooth device follows in hopping between each of the 79 1-MHz bands that constitute the Bluetooth spectrum. Each piconet has its own channel sequence that is used to minimize interference with other devices.

Connectable device - Any Bluetooth device that is in range and will respond to a page message by setting up a connection.

Destination - The Bluetooth device that will receive the action from another Bluetooth device. The sending device is called a source.

Device Address - A unique 48-bit address that is assigned to a Bluetooth device to identify it to other Bluetooth devices.

Device Name - A friendly device name specified by the user. For example, you could call your mobile phone "Bill's mobile phone" which makes it easier to identify than looking up its model number or noting its device address. This name will be made available during discovery and will be listed as part of the piconet when the device is in range.

Device Security Level - Bluetooth devices can have two levels of security-trusted and untrusted. Other Bluetooth devices can be set to respond differently depending on the device security level of the Bluetooth device with which they are connecting.

Discoverable - Any Bluetooth device in range that will respond to an inquiry message is "discoverable" by other Bluetooth devices. In general, devices should be put in discoverable mode only when you are seeking to pair them. A shared printer is an exception to this rule since it should be discoverable to everyone.

Discovery - This is the procedure by which one Bluetooth device requests and receives the Bluetooth device address, name, and other information about another Bluetooth device, usually before they have been paired. By setting the devices to "discoverable," they are enabled to "see" each other when they go out looking for discoverable devices. This allows the user to pair the devices so they will look for and always be able to see each other.

Frequency hopping - Bluetooth devices do not stay on the same frequency. Rather, they "hop" from one of 79 frequency in the 2.45 GHz range to the next at a rate of 1600 hops per second. This is done to minimize interference and to prevent interception of the signal. Each Bluetooth piconet will have its own unique channel hopping sequence so that the devices can communicate with each other without disturbing or being infiltrated by other devices.

Headset - A microphone and earpiece (or earpieces for a stereo headset) that receives sound and data transmissions from another Bluetooth device and sends sound and data back.

Hold mode - Once a device has been synchronized to the piconet, it can be programmed to go into hold mode. In this mode, the device uses minimal energy while still keeping the clock running so that it can be brought out of hold instantly once a request for data transfer has been made. Hold mode uses less energy than sniff mode but more energy than park mode.

Idle Mode - A device in idle mode has no established links to other devices. It can send out periodic inquiries to find out if any other devices are in range or it can wait for an inquiry from another device.

In Range - A device is in range if another Bluetooth device can detect it and establish a connection. This is not a set distance but is generally said to be around 10 meters (33 feet). Bluetooth signals can go through walls, but the range can be affected by various external factors.

Inquiry - A Bluetooth device sends out an inquiry to discover which devices are in range. If the devices have been paired, it will establish a connection using the paging procedure. Otherwise, it will simply note that the device is in range and wait for instructions from the user.

Interference - Bluetooth wireless technology is based on radio waves in the 2.45 GHz spectrum. Other non-Bluetooth devices such as cordless phones, garage door openers, and baby monitors also use this frequency band. Although it is uncommon, these devices can interfere with Bluetooth devices, garbling portions of the signal.

Master - The Bluetooth device in a piconet that is given control over the other devices, called slaves. This device is used to specify the channel hopping sequence and to synchronize the other devices. The term master is also used to refer to any device that initiates action or requests a service on the piconet. In this sense, every device on the piconet can play the role of master or slave depending on who needs information and which way that information needs to flow.

Paging Procedure - This is the procedure by which an actual connection is established between two devices. The paging procedure typically follows a successful inquiry procedure in which two devices become aware of each other.

Paired/Pairing - Two Bluetooth devices that will regularly be used with each other may be taught to recognize each other automatically via a process called "pairing." This allows automatic actions to occur between the two devices. When turned on, the devices will look for each other and establish a connection if they are in range. Usually a passkey is require to authenticate the connection and keep unauthorized pairing from occurring. A typical example of pairing would be a Bluetooth headset to go with a mobile phone. You don't want to have to through a discovery procedure every time you turn the headset on. By pairing the headset with the phone, you can have the headset find the phone automatically forever after.

Park Mode - In park mode, a Bluetooth device is still fully synchronized to the piconet, but it doesn't participate in the traffic. It will occasionally check to make sure it is still synchronized but will not perform any other actions. Park mode uses less energy than hold mode and sniff mode.

Passkey - A passkey is a user-specified code that will authenticate incoming connections among paired devices. This prevents other devices from masquerading as the authorized device. The passkey is unique to the connection, not to the device. Your mobile phone can have one passkey that connects it to the headset and another passkey that connects it to your laptop.

Piconet - A collection of Bluetooth devices that have been paired together with one master and up to seven slaves. This collection is ad hoc and can change as other devices come in range or go out of range. All devices in the piconet use the same channel hopping sequence, specified by the master, and can communicate with each other.

Scatternet - Two or more independent and non-synchronized piconets form a scatternet. The term "scatternet" is most often used to refer to two or more piconets in which a device in one of the piconets is also paired with a device or devices in another piconet.

Service Discovery - Bluetooth devices can discover each other's existence via the discover process. Service discovery takes this one step further by listing what services or tasks are available via that device.

Slave - A device on the piconet that is not the master. Also, any device on the piconet that is responding to the action of another or to a request for service. (See master.)

Sniff mode - In sniff mode, a slave device still listens to the other devices on the piconet, but at a reduced rate. This saves a bit of energy, but not as much as hold mode or park mode.

Source - The Bluetooth device initiating action to another (destination) device.