Bluetooth Glossary

Bluetooth glossary of terms acronyms The following is a list of most of the terms used in the Bluetooth technology, and serves as a quick look-up guide. This glossary is partly based on the Glossary originally supplied in the Motorola Bluetooth website, my thanks to them. However this glossary contains much more lower layer information, removes the reams of superfluous terms, and elaborates on many points. In effect it is a totally different list, and (I think) much better and clearer.

2-in-1 Handset: The situation where a subscriber handset is acting as a remote handset to a base unit which provides a network connection.

3G: Third generation. Refers to the next generation of digital phone technology (such as UMTS). Also see 3G Resource Center.

802.11 WLAN: A Wireless Lan specification defined by the IEEE. Also see IEEE 802.11 Resource Center.

Access Code: Each baseband packet starts with an Access code, which can be one of 3 types, CAC, DAC & IAC. The CAC consists of a preamble, sync word and trailer, and its total length is 72 bits. When used as a self-contained message without a packet header, the DAC and IAC do not include the trailer bits and are of length 68 bits.


ACK: Acknowledge.

ACL: Asynchronous Connectionless Link.One of the two types of data links defined for the Bluetooth Systems, it is an asynchronous (packet-switched) connection between two devices created on the LMP level. This type of link is used primarily to transmit ACL packet data. The other data link type is SCO.

ACO: Authenticated Ciphering Offset.

Active Mode: In the active mode, the Bluetooth unit actively participates on the channel. The master schedules the transmission based on traffic demands to and from the different slaves. In addition, it supports regular transmissions to keep slaves synchronised to the channel. Active slaves listen in the master-to-slave slots for packets. If an active slave is not addressed, it may sleep until the next new master transmission.

AM_ADDR: Active Member Address. It is a 3 bit number.It is only valid as long as the slave is active on the channel. It is also sometimes called the MAC address of a Bluetooth unit.

AP: Access Point.


AR_ADDR: Access Request Address. This is used by the parked slave to determine the slave-to-master half slot in the access window it is allowed to send access request messages in. It is only valid as long as the slave is parked and is not necessarily unique.

ARQN: Automatic Repeat reQuest Number is used as a 1-bit acknowledge indication to inform the source of a successful transfer of payload data with CRC.


authentication: The process of verifying 'who' is at the other end of the link. Authentication is performed for devices. In Bluetooth, this is achieved by the authentication procedure based on the stored link key or by pairing (entering a PIN).

authentication device: A device whose identity has been verified during the lifetime of the current link based on the authentication procedure.



AUX: An ACL link packet type for data. An AUX1 packet resembles a DH1 packet except it has no CRC code. As a result it can can carry up to 30 info bytes.

baseband: The baseband describes the specifications of the digital signal processing part of the hardware -- the Bluetooth link controller, which carries out the baseband protocols and other low-level link routines.

BB: Abbreviation of Baseband.

BD: Bluetooth device

BD_ADDR: Bluetooth Device Address. Each Bluetooth transceiver is allocated a unique 48-bit device address. It is divided into a 24-bit LAP field, a 16-bit NAP field and a 8-bit UAP field.

BER: Bit Error Rate

Bluetooth: An open specification for wireless communication of data and voice. It is based on a low-cost short-range radio link facilitating protected ad hoc connections for stationary and mobile communication environments. Also see Bluetooth Resource Center.

Bluetooth clock: Every Bluetooth unit has an internal system clock which determines the timing and hopping of the transceiver. It is never adjusted or turned off. It can be implemented as a 28-bit counter, with the LSB ticking in units of 312.5us, giving a clock rate of 3.2kHz.

Bluetooth device class: A parameter that indicates the type of device and which types of services that are supported. The class is received during the discovery procedure.

Bluetooth service type: One or more services a device can provide to other devices. The service information is defined in the service class field of the Bluetooth device class parameter.


BT: Bluetooth (unofficial short form).


business card: The electronic date equivalent to a printed business card. This electronic version of the business card is treated like a file and can be exchanged between Bluetooth devices.

CAC: Channel Access Code
CDMA: Code Division Multiple Access. CDMA is a digital cellular communications technology. Each call has a individual code to identify the call. Multiple calls can be grouped together on a single frequency. CDMA uses spread-spectrum techniques for handling radio communications. CDMA is an improvement on AMPS and TDMA cellular service. Also see CDMA Resource Center.


channel: A logical connection on the L2CAP level between two devices serving a single application or higher layer protocol.

Channel (hopping) sequence: This is a pseudo-random sequence of 79 (23 for the 23MHz system) frequencies, The frequency is calculated using the BD_ADDR of the master of the piconet. The phase in the sequence is derived from an estimate of the master's clock. The channel hopping sequence has a very long period length, does not show repetitive patterns over a short time interval, but which distributes the hop frequencies equally over the 79 (23 for the 23MHz system) MHz during a short time interval .See also Frequency sequence.

Circuit Switched: The application of a network where a dedicated line is used to transmit information. Only one user may employ the resources of the line at a time.

Circuit Switched Bluetooth: The application of a network where a dedicated line is used to transmit bluetooth data.

CL: Connectionless.

class of device: See Bluetooth device class. Also abbreviated as CoD.

CLK: Clock, typically the master device clock which defines the timing used in the piconet.

CLKE: Clock Estimate, a slave's estimate of the master's clock, used to synchronise the slave device to the master.

CLKN: Clock Native, the clock of the current Bluetooth Device

CO: Connection-oriented.

CoD: Class of Device.

connectable device: A Bluetooth device in range that will respond to a page message and set up a connection


CP: Capability Provider. A Capability Provider is a module within the local device that provides a service to other modules. Protocol stack modules (RFCOMM, L2CAP) are Capability Providers. So are "application interface modules" such as OBEX and ESC-AT. In fact, any module that registers a port that other modules can connect to is a Capability Provider.

CRC: Cyclic Redundancy Check. This is a 16-bit code added to the packet to determine whether the payload is correct or not. CRC data payloads can be carried only be DM, DH or DV packets. The CRC code is generated by the CRC-CCITT polynomial 0x11021 (hex).

CTP: Cordless Telephone Profile.

CVSD: Continuous Variable Slope Delta Modulation.

DAC: Device Access Code. It is used during page, page scan and page response substates. It is a code derived from the unit's BD_ADDR.

DCI: Default Check Initialisation. Within Bluetooth , the DCI is defined to be 0x00 (hexadecimal).
DCID: Destination Channel Identifier, used as the device local end point for an L2CAP transmission. It represents the channel endpoint on the device receiving the message. It is a device local name only. See also SCID.


destination: The Bluetooth device receiving an action from another Bluetooth device. The device sending the action is called the source. The destination is typically part of an established link, though not always ( such as in inquiry / page procedures).

Device Discovery: The mechanism to request and receive the Bluetooth address, clock, class of device, used page scan and names of devices.


device name: See Bluetooth device name.

device security level: Access to a device can be denied based on the required device security level. There are two levels of device security: trusted device and untrusted device. See also service security level.

DH: Data-High Rate. An ACL link data packet type for high rate data. DH1 packets are similar to DM1 packets, except the info in the payload is not FEC encoded. This means the DH1 packet can carry up to 28 info bytes and covers a single time slot. The DH3 is the same except it can cover up to 3 time slots and contain up to 185 info bytes. The DH5 packet is the same again except it can cover up to 5 time slots and contains up to 341 info bytes See also Bluetooth packet types.

DIAC: Dedicated Inquiry Access Code, used when you wish to inquire for certain, specific types of devices.

discoverable device: A Bluetooth device in range that will respond to an inquiry message.

DLCI: Data Link Connection Identifier. This is a 6-bit value representing an ongoing connection between a client and a server application. It is used in the RFCOMM layer.

DM: Data - Medium Rate. An ACL link data packet type for medium rate data. DM1 packets carry information data only, contining a 16-bit CRC code and up to 18 info bytes. They are encoded using 2/3 FEC and the packet can cover up to a single time slot. DM3 packets are the same except they can cover up to 3 time slots, and can carry up to 123 info bytes. DM5 packets are the same again except they can cover up to 5 time slots and can hold up to 226 info bytes. See also Bluetooth packet types.

DSR: Data Set Ready. A device sets an RS-232 DSR signal when it is ready to accept data.

DT: Data Terminal.


DV: Data Voice. A SCO link data packet type for data and voice.It is divided into a voice field of 80 bits and a data field of 150 bits. The voice field is not covered by FEC, but the data field is covered by 2/3 FEC. The voice and data fields are treated completely separate. The voice field is handled like normal SCO data and is never retransmitted; that is, the voice field is always new. The data field is checked for errors and is retransmitted if necessary. See also Bluetooth packet types.


ETSI: European Telecommunications Standards Institute.


FEC: Forward Error Correction. The purpose of the FEC scheme on the data payload is to reduce the number of retransmissions. Within Bluetooth , there are 2 versions of this, 1/3 FEC and 2/3 FEC. 1/3 FEC is a simple 3-times repetition of each info bit. 2/3 FEC is a (15,10) shortened Hamming code.

FH: Frequency Hopping.

FHS: Frequency Hopping Synchronization. This a special control packet revealing, among other things, the BD_ADDR and the clock of the source device. It contains 144 info bits and a 16-bit CRC code. The payload is coded with a rate 2/3 FEC which brings the total payload length to 240 bits. The FHS packet covers a single time slot. See also Bluetooth packet types.

FIFO: First In, First Out.


Frequency Hopping (Selection): Bluetooth is characterised by its system of fast frequency hops. 10 different types of hopping sequences are defined, 5 of the 79 MHz range/79 hop system and 5 for the 23 MHz range/23 hop system. The different range system's hopping sequences differ only in frequency range 79MHz / 23MHz, and segment length : 32 hops(79MHz system) / 16 hops(23MHz system).; The individual hopping sequences include the page sequence and the page response sequence, these are used in the page procedure. Used in the inquiry procedure are the inquiry sequence and the inquiry response sequence. Finally the main hopping sequence used in the bluetooth system is the channel hopping sequence


GAP: Generic Access Profile. This profile describes the mechanism by which one device discovers and accesses another device when they do not share a common application.

GFSK: Gaussian Frequency Shift Keying. This is the modulation used in the radio layer of the Bluetooth system.

GIAC: General Inquire Access Code. The default inquiry code which is used to discover all devices in range.

GM: Group Management.

GOEP: Generic Object Exchange Profile.


GSM: Global System for Mobile communications. GSM is a digital cellular communications technology that is available in Europe and the US. GSM offers multiple services for the subscriber such as short message service.



GW: Gateway. A Bluetooth enabled base-station which is connected to an external network.


HCI: Host Controller Interface. An (application-optional) layer which provides a command interface to the LMP and Baseband layers.


headset: A microphone and earpiece used to conduct conversations. Headsets can be connected directly to a cellular device or remotely using Bluetooth communications technology.

HEC: Header-Error-Check. An 8-bit word normally generated by using the UAP of the master device. There are 2 exceptions: in the case of FHS packets using the master page response, the slave UAP is used and for FHS packets sent in inquiry response the DCI value is used.


hold mode: Devices synchronised to a piconet can enter power-saving modes in which device activity is lowered. The master unit can put slave units into HOLD mode, where only an internal timer is running. Slave units can also demand to be put into HOLD mode. Data transfer restarts instantly when units transition out of HOLD mode. It has an intermediate duty cycle (medium power efficient ) of the 3 power saving modes (sniff, hold & park).

HS: Headset. Also see Bluetooth Headsets.

HV: High quality Voice. A SCO link voice packet. HV1 packets carry 10 info bytes, which are protected by 1/3 FEC. HV2 packets carry 20 info bytes, and are protected by 2/3 FEC. HV3 packets carry 30 info bytes, and not protected by FEC. HV packets do not have a CRC or payload header.See also Bluetooth packet types.

IAC: Inquiry Access Code. Used in inquiry procedures, can be one of 2 types: Dedicated IAC, for specific devices, or Generic IAC for all devices.

ID packet: A 68-bit packet used in paging , inquiry and response routines. It is essentially the device access code (DAC) or inquiry access code (IAC). See also Bluetooth packet types.

Idle mode: A device is in idle mode when it has no established links to other devices. In this mode, the device may discover other devices. In general, a device sends inquiry codes (GIAC, DIAC to other devices. Any device that allows inquiries will respond with information. The devices may then decide to form a link.

IEEE: Institute of Electronic and Electrical Engineering. http://www.ieee.org/

Inquiry Procedure: The inquiry procedure enables a device to discover which devices are in range, and determine the addresses and clocks for the devices. The inquiry procedure involve a unit (the source)sending out inquiry packets (inquiry state) and then receiving the inquiry reply .The unit that receives the inquiry packets (the destination), will hopefully be in the inquiry scan state to receive the inquiry packets. The destination will then enter the inquiry response state and send an inquiry reply to the source. After the inquiry procedure has completed, a connection can be established using the paging procedure.


Inquiry Response State: When a device have received an inquiry packet, it can respond with an inquiry reply packet (an FHS packet). It will send this using the inquiry response hopping sequence.
Inquiry State: When a device wishes to discover new devices , it enters the inquiry state, where it broadcasts inquiry packets (ID packets), containing the IAC, to all devices in range. It will send these using the inquiry hopping sequence. The device in the Inquiry state can also receive inquiry replies (FHS packets), however it will not acknowledge these packets.

Inquiry Scan State: When a device wishes to receive inquiry packets it enters the inquiry scan mode. The scanning will follow the inquiry hopping sequence.

Inquiry (hopping) sequence: This is a sequence of 32 (16 for the 23MHz system) frequencies, The frequency is calculated using the GIAC LAP or the DIAC LAP. The phase in the sequence is derived from the native unit's clock. 32 frequencies are calculated , the main centre frequency and 31 other frequencies, these have an of offset of +/- 16. A new centre frequency is calculated every 1.28s. To handle all 32 frequencies , the inquiry hopping sequence switches between 2 inquiry trains , of 16 frequencies each. See also Frequency sequence.

Inquiry (hopping) response sequence: The inquiry response sequence covers 32 (16 for the 23MHz) unique response frequencies that all are in an one-to-one correspondence to the current inquiry hopping sequence. The master and slave use different rules to obtain the same sequence. See also Frequency sequence.

ISM: Industrial, Scientific, Medical.

ITU: International Telecommunication Union. http://www.itu.int
The ITU, headquartered in Geneva, Switzerland is an international organization within the United Nations System where governments and the private sector coordinate global telecom networks and services.


known device: A device for which at least the BD_ADDR is stored.

L2CAP: Logical Link Controller and Adaptation Protocol. This protocol supports higher level protocol multiplexing, packet segmentation and reassembly, and the conveying of quality of service information.

L_CH: Logical Channel.

LAN: Local Area Network.

LAP: LAN Access Point.

LAP: Lower Address Portion. A 24-bit section of the BD_ADDR.See also NAP & UAP.

LC: Link Controller. The Link Controller manages the link to the other Bluetooth devices. It is the low-level baseband protocol handler.

LC Channel: Link Control control channel. One of the 5 logical channels defined for the bluetooth system. It is mapped onto the packet header. It control low level link control info. The LC is carried in every packet except the ID packet which has no packet header.


LFSR: Linear Feedback Shift Register. Used in bluetooth to generate the HEC and CRC.

link key: The authentication key used to establish a link between devices. See also bonding.

LM: Link Manager. The Link Manager software entity carries out link setup, authentication, link configuration, and other protocols.

LM Channel: Link Manager control channel. One of the 5 logical channels defined for the bluetooth system. It carries control info exchanged between the link managers of the master and the slave(s). It can be carried by either the SCO or ACL link.

LMP: Link Manager Protocol. The LMP is used for link setup and control. The LMP PDU signals are interpreted and filtered out by the Link Manager on the receiving side and are not propagated to higher layers.

LMP-authentication: An LMP level procedure for verifying the identity of a remote device. The procedure is based on a challenge-response mechanism using a random number, a secret key and the BD_ADDR of the non-initiating device. The secret key used can be a previously exchanged link key or an initialization key created based on a PIN (as used when pairing).

LMP-pairing: A LMP procedure that authenticates two devices based on a PIN and subsequently creates a common link key that can be used as a basis for a trusted relationship or a (single) secure connection. The procedure consists of the steps:; 1: creation of an initialization key (based on a random number and a PIN),; 2: LMP-authentication based on the initialisation key and; 3: creation of a common link key.


Logical Channel: There are 5 logical channels defined for the Bluetooth system. The LC & LM control channels, and the UA, UI & US user channels. The LC channel is carried in the packet header, all other channels are carried in the packet payload. See the individual sections for more details.

LSB: Least Significant Bit.


MAC Address: 3-bit address to distinguish between units participating in the piconet. Within Bluetooth, this is the AM_ADDR .


MAN: Metropolitan Area Network.
: .

master device: A device that initiates an action or requests a service on a piconet. Also the device in a piconet whose clock and hopping sequence are used to synchronize all other devices in the piconet.See also LocDev.


MS: Mobile Station. A generic term for the mobile device in question (GSM phone, Bluetooth device etc).


MSB: Most Significant Bit.


MSC: Message Sequence Chart.

MT: Mobile Terminal, same as Mobile Station.



MUX: Multiplexing Sublayer. A sublayer of the L2CAP layer.




Name Discovery: The mechanism to request and receive a device name.

NAP: Non-significant Address Portion. A 16-bit section of the BD_ADDR. See also LAP & UAP.


non-connectable device: A device that does not responds to paging is said to be in non-connectable mode. The opposite of a non-connectable device is a connectable device.


non-discoverable device: A device that cannot respond to an inquiry is said to be in non-discoverable mode. The device will not enter the inquiry response state in this mode.


NULL packet: A 126-bit packet consisting of the CAC and packet header only. It is used to return link information to the source. The NULL packet does not have to be acknowledged .See also Bluetooth packet types.


OBEX: Object EXchange Protocol.


Packet Format: Each packet consists of 3 entities, the access code, the packet header and the payload. Their are a number of different packet types.

Packet Header: The header contains link control info and consists of 6 fields: AM_ADDR : active member address, TYPE : type code , FLOW : flow control, ARQN : acknowledge indication, SEQN : sequence number & HEC : header error check. The total size of the header is 54-bits.

Packet Switched: A network that routes data packets based on an address contained in the data packet is said to be a packet switched network. Multiple data packets can share the same network resources.


Packet type: 13 different packet types are defined for the baseband layer of the Bluetooth system. All higher layers use these packets to compose higher level PDU's. The packets are ID, NULL, POLL, FHS , DM1 ; these packets are defined for both SCO and ACL links. DH1, AUX1, DM3, DH3, DM5, DH5 are defined for ACL links only. HV1, HV2, HV3 , DV are defined for SCO links only


Page (hopping) sequence: This is a sequence of 32 (16 for the 23MHz system) frequencies, Each frequency is calculated using the unit being paged's BD_ADDR (this was obtained earlier, such as an inquiry operation ). The phase in the sequence is derived from an estimate of the unit being paged's clock. Although it should be able to theoretically calculate the predicated hop frequency of the unit being paged, and page it straight away, inevitably clock drift will occur. 32 frequencies are used to handle this, using the calculated main centre frequency and 31 other frequencies, these have an of offset of +/- 16. A new centre frequency is calculated every 1.28s. To handle all 32 frequencies , the page hopping sequence switches between 2 paging trains , of 16 frequencies each. See also Frequency sequence.

Page (hopping) response sequence: The page response sequence covers 32 (16 for the 23MHz) unique response frequencies that all are in an one-to-one correspondence to the current page hopping sequence. The master and slave use different rules to obtain the same sequence. See also Frequency sequence.

Page (Master) Response State: Step 1:When the source has received a reply to it's original page message, it will enter this state. It will then send an FHS packet to the destination device. It will send this using the page hopping sequence.; Step 2:When the source has received the second reply (Page Slave Response State: Step2), it knows that the destination device has received the FHS packet the source sent in Step 1. The source is now the master of the destination (the slave).

Page (Slave) Response State: Step 1: Once a destination device has received its own DAC from the source (in the ID packet), it will enter this state. It will send a response message (its DAC again) to the source .It will send this using the page response hopping sequence.; Step 2:Once the destination device has received the FHS packet from the source ,(Page Master Response State: Step 1), the destination will send a reply to the source (an ID packet containing the destination DAC).; Step 3: The destination will switch to the source's channel params. The destination is now the slave of the source (the master).


Page Scan State: A mode where a device listens for page trains containing its own device access code (DAC). When a device wishes to receive page packets it enters the page scan mode. The scanning will follow the page hopping sequence. If a device receives a page packet, it will enter the slave response state.

Page State: A mode that a device enters when searching for other devices. The device sends out a page packet (ID packet), using the page hopping sequence, to notify other devices that it wants to know about the other devices and/or their services.


Paging Procedure: With the paging procedure, an actual connection can be established. The paging procedure typically follows the inquiry procedure. Only the Bluetooth device address is required to set up a connection. Knowledge about the clock (clock estimate) will accelerate the setup procedure. A unit that establishes a connection will carry out a page procedure and will automatically be the master of the connection. The procedure occurs as follows:
: 1: A device (the source) pages another device (the destination ) : Page state
: 2: The destination receives the page : Page Scan state
: 3: The destination sends a reply to the source. : Slave Response state: Step 1
: 4: The source sends an FHS packet to the destination : Master Response state: Step 1

5: The destination sends it's second reply to the source. : Slave Response state : Step 2: 6: The destination & source then switch to the source channel parameters :Master Response state: Step 2 & Slave Response state: Step 3

pairable mode: A device that accepts pairing, is said to be in pairable mode. The opposite of pairing mode is non-pairable mode.

pairing: The creation and exchange of a link key between two devices. The devices use the link key for future authentication when exchanging information.

park mode: In the PARK mode, a device is still synchronized to the piconet but does not participate in the traffic. Parked devices have given up their MAC (AM_ADDR) address and occasional listen to the traffic of the master to re-synchronize and check on broadcast messages. It has the lowest duty cycle (power efficiency) of all 3 power saving modes (sniff, hold & park).

payload format: Each packet payload can have one of 2 possible fields, the data field (ACL) or the voice field (SCO). The different packets, depending on whether they are ACL or SCO packets can only have one of these fields. The one exception is the DV packets which have both. The voice field has a fixed length field, with no payload header. The data field consists of 3 segments: a payload header, a payload body and a CRC code (with the exception of the AUX1 packet).

PCM: Pulse Coded Modulation.

PDU: Protocol Data Unit. (i.e., a message.)


Physical link: A synchronized Bluetooth baseband-compliant RF hopping sequence. It is a baseband level association between two devices established using paging. A physical link comprises a sequence of transmission slots on a physical channel alternating between master and slave transmission slots.

Piconet: A collection of devices connected via Bluetooth technology in an ad hoc fashion. A piconet starts with two connected devices, such as a portable PC and cellular phone, and may grow to eight connected devices. All Bluetooth devices are peer units and have identical implementations. However, when establishing a piconet, one unit will act as a master and the other(s) as slave(s) for the duration of the piconet connection. All devices have the same physical channel defined by the master device parameters (clock and BD_ADDR).

PIN: Personal Identification Number. The Bluetooth PIN is used to authenticate two devices that have not previously exchanged link key. By exchanging a PIN, the devices create a trusted relationship. The PIN is used in the pairing procedure to generate the initial link that is used for further identification.

PIN(BB): The PIN used on the baseband level. The PIN(BB) is used by the baseband mechanism for calculating the initialization key during the pairing procedure. (128 bits)

PIN(UI): The PIN used on the user interface level. The PIN(UI) is the character representation of the PIN that is entered on the UI level.

PM_ADDR: Parked Member Address. It is a 8-bit member (master-local) address that separates the parked slaves.The PM_ADDR is only valid as long as the slave is parked.


POLL packet: Similar to the NULL packet, except it requires a confirmation from the destination. Upon reception of a POLL packet the slave must respond with a packet. See also Bluetooth packet types.


PPP: Point to Point Protocol.

PRBS: Pseudorandom Bit Sequence.


Profile: A description of the operation of a device or application.


PSTN: Public Switched Telephone Network. The general phone network.

QoS: Quality of Service.

Radio: The Radio layer of the Bluetooth system, the lowest defined layer. It details the requirements needed for a Bluetooth device transceiver to operate in the Bluetooth radio band . 2 different ranges have been defined for the radio layer, a 23MHz range and a 79MHz range , both are in the 2.4GHz ISM band. The 23MHz range is only used in certain countries (such as Spain, France) , that have national limitations on the amount of frequencies available. Different hop systems are used for both.


RF: Radio Frequency.


RFCOMM: Serial Cable Emulation Protocol based on ETSI TS 07.10.

RS-232: A serial communications interface. Serial communication standards are defined by the Electronic Industries Association (EIA).

RSSI: Received Signal Strength Indication. An optional part of the radio layer, used to determine the link quality and thus whether to increase broadcast power.

RTX Timer: The Response Timeout eXpired timer used in the L2CAP layer to terminate the channel when the remote endpoint is unresponsive to signalling requests. It is started when a signalling request is sent to a remote device.

RX: Receiver.

S: Short for Slave. See slave device.

SAP: Service Access Points (APs).

SAR: Segmentation and Reassembly. A sublayer of the L2CAP layer.

Scatternet: Multiple independent and non-synchronized piconets form a scatternet.

SCO: Synchronous Connection Oriented link. One of the 2 bluetooth data link types defined.A synchronous (circuit-switched) connection for reserved bandwidth communications, e.g. voice, between two devices created on the LMP level by reserving slots periodically on a physical channel. This type of link is used primarily to transport SCO packets (voice data). SCO packets do not include a CRC and are never retransmitted. It primarily supports time-bounded information like voice. (Master to single slave.) SCO links can be established only after an ACL link has first been established. See also ACL.

SCID: Source Channel Identifier. Used in the L2CAP layer to indicate the channel endpoint on the device sending the L2CAP message. It is a device local name only. See also DCID.



SDAP: Service Discovery Application Profile.

SDDB: Service Discovery Database.

SDP: Service Discovery Protocol. It is a Bluetooth defined protocol for provided for or available through a Bluetooth device. Essentially provides a means for applications to discover which services are available and to determine the characteristics of those available services.

SDP client: The SDP client may retrieve information from a service record maintained by the SDP server by issuing an SDP request.

SDP server: The SDP server maintains a list of service records that describe the characteristics of services associated with the server.

SDP Session: The exchange of information between an SDP client and an SDP server. The exchange of information is referred to as an SDP transaction.

SDP Transaction: The exchange of an SDP request from an SDP client to an SDP server, and the corresponding SDP response from an SDP server back to the SDP client.


Security Mode 1: A device will not initiate any security. A non-secure mode.

Security Mode 2: A device does not initiate security procedures before channel establishment on L2CAP level This mode allows different and flexible access policies for applications, especially running applications with different security requirements in parallel. A service level enforced security mode.

Security Mode 3: A device initiates security procedures before the link setup on LMP level is completed. A link level enforced security mode.

SEQN: Sequential Numbering scheme. It provides a sequential numbering scheme to order the data packet stream.


Serial Interface: An interface to provide serial communications. service This term refers to a service that one device provides for others. Examples are printers, PIM. synchronization servers, modems (or modem emulators).


Service (SDP layer): A service is any entity that can provide information, perform an action, or control a resource on behalf of another entity. A service may be implemented as software, hardware, or a combination of hardware and software.

Service Advisor: The portion of the UI that handles BT services for the UI.

Service Attribute: Each service attribute describes a single characteristic of a service.

Service Discovery: See SDP.

Service Class: Each service is an instance of a service class. The service class definition provides the definitions of all attributes contained in service records that represent the instances of that class.

Service Layer: The group of protocols that provides services to the application layer and the driver layer in a Bluetooth device.

Service Record: A service record contains all of the information about a service that is maintained by an SDP server.

Service Record Database: A database that contains the service discovery-related information.

Service Record Handle: A service record handle is a 32-bit number that uniquely identifies each service record within an SDP server.


SIG: Special Interest Group. The Bluetooth SIG is located at www.bluetooth.com.



slave device: A device in a piconet that is not the master.There can be many slaves per piconet.


sniff mode: Devices synchronized to a piconet can enter power-saving modes in which device activity is lowered. In the SNIFF mode, a slave device listens to the piconet at reduced rate, thus reducing its duty cycle. The SNIFF interval is programmable and depends on the application. It has the highest duty cycle (least power efficient ) of all 3 power saving modes (sniff, hold & park).

source: The Bluetooth device initiating an action to another Bluetooth device. The device receiving the action is called the destination. The source is typically part of an established link, though not always ( such as in inquiry / page procedures).

SR: Scan Repetition. A mode used in the baseband layer to determine how long the device will continue to scan for a page response



TCP/IP: Transport Control Protocol/Internet Protocol ( more... ).

TCS: Telephone Control protocol Specification.

TCS-AT: A set of AT-commands by which a mobile phone and modem can be controlled in the multiple usage models. In BT, AT-commands are based on ITU-T recommendation v.250 and ETS 300 916(GSM 07.07). In addition, the commands used for fax services are specified by the implementation. TCS-AT will also be used for dial-up networking and headset profiles.

TCS Binary: Bluetooth Telephony Control protocol Specification using bit-Oriented protocol. It is also referred to as the TCS-BIN system. TCS-BIN will be used for cordless telephony profiles.

TDD: Time Division Duplex


TGAP: Timer used in the General Access Profile (GAP).


time slot: A single time slot in the Bluetooth system lasts 625us. It can be though of as the time it takes to send one packet from one Bluetooth device to another


TTP: Tiny Transport Protocol between OBEX and UDP [TBD].

TX: Transmit.

UA Channel: User Asynchronous data channel. One of the 5 logical channels defined for the bluetooth system. The UA channel carries L2CAP transparent asynchronous user data. It is normally carried in the ACL link.

UAP: Upper Address Portion. A 8-bit section of the BD_ADDR. See also LAP & NAP.

UART: Universal Asynchronous Receiver Transmitter. A device which converts parallel data into serial data for transmission, or it converts serial data into parallel data for receiving data.

UC: User Control.


UDP/IP: User Datagram Protocol/Internet Protocol.

UI Channel: User Isochronous data channel. One of the 5 logical channels defined for the bluetooth system. The UI channel carries L2CAP transparent isochronous user data. It is normally carried in the ACL link. It is supported by timing start packets at higher levels


UMTS: Universal Mobile Telecommunications System. Also see 3G Resource Center.


US Channel: User Synchronous data channel. One of the 5 logical channels defined for the bluetooth system. The US channel carries transparent synchronous user data. It is carried in the SCO link only.

UUID: Universal Unique Identifier. Used in the SDP layer.

WAN: Wide Area Network.

WLAN: Wireless Local Area Network. Also see IEEE 802.11 Resource Center.