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What is Bluetooth?
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Bluetooth is an alliance between mobile communications and mobile computing companies to develop a short-range communications standard allowing wireless data communications at ranges of about 10 meters. Bluetooth will encompass both a standard communications interface and a low-cost computer chip. It is a cross between the DECT (Digital European Cordless Telephone) and iRDA (infra Red Data Association) technologies. Bluetooth was conceived by Ericsson, but founded by Nokia, Ericsson, IBM, Intel and Toshiba. The Bluetooth Interest Group has since been joined by hundreds of companies including One2One; a UK mobile network operator, Motorola, Qualcomm, Compaq, Dell, 3Com Palm, VLSI, Xircom, Psion Dacom and Lucent. Bluetooth does NOT involve mobile network transactions- its spectrum is freely available to use in the unlicensed spectrum area (at 2.45 gigahertz). Data transmission speeds using Bluetooth are expected to be between 720 kbps and one megabit per second (Mbps).

Bluetooth will facilitate wireless Local Area Networks in which networks of different handheld computing terminals and mobile terminals can communicate and exchange data, even on the move and when there is no line-of-sight between those terminals. Bluetooth will mean that if users have several (Bluetooth-enabled) portable terminals, they can nonetheless use them with all the advantages of an integrated smart phone, without having to re-enter data or find the most recent versions on different terminals.

This kind of synchronization and exchange of data are Bluetooth’s major applications, as are electronic commerce applications such as electronically paying for parking meters, bus tickets, shopping, movies and so on. Smart offices are envisaged in which an employee with a Bluetooth device is automatically checked in when entering the building and this triggers a series of actions such as lights and PCs being switched on. The Bluetooth partners see one of its main advantages as being that it does not need to be set up- Bluetooth runs in the background and line of sight is not even needed for the machines to automatically initiate and trigger processes. Such proactive intelligence could turn out to be a nuisance rather than a convenience for Bluetooth users unless it is under the control of the device owner(s). Indeed, the Bluetooth standard does incorporate these kinds of control mechanisms, since each device is assigned a unique 12 byte address and to connect to that device, its address must be known. There will also be an enquiry feature so to search for other Bluetooth-enabled devices within range.

The Bluetooth specification was outlined in early 1999, with Bluetooth-enabled mobile terminals such as laptops, smart phones, handheld computers and so on likely to be first available by the industry conference "Telecom 99" in Geneva, Switzerland. Commercial Bluetooth terminals are expected to be available in the year 2000.

In one negative prediction for Bluetooth, the September 1998 issue of "Wired" magazine listed Bluetooth at position one in its "Hype List" which aims at "Deflating this month’s overblown memes". It commented that "This wireless LAN technology overcomes infrared’s line-of-sight limitations, but Bluetooth’s true application, much less its market potential, won’t emerge until there’s a critical mass of RF-chip PCs, handhelds, and phones. And even then, people looking to move data between gadgets might find it hard to sever their emotional connection to the entrenched wireline option." Bluetooth was given a life expectancy of 24 months. Whilst it is true to say that other similar ideas to network electronic terminals and household appliances have come and gone in the past, such as Novel NetWare, Bluetooth does have the backing of a lot of market leading mobile phone and modem manufacturers. Others have failed because they have not been able to achieve a critical mass of wired appliances when licensing their technology.

Bluetooth Components
Any Bluetooth solution consists of four major components: antenna/RF component, Bluetooth hardware and firmware (baseband and Link Controller), Bluetooth software protocol stack, and the application itself. Each of these components is a product in itself, and companies exist that have entire business models based around solving only one of these four areas.

Antenna/RF: The antenna and RF design portion is interesting in that it requires a unique solution for each device. When purchasing a Bluetooth module for Ericsson, for instance, the antenna is not provided. Bluetooth silicon manufacturers cannot effectively provide an antenna with the hardware. Even single chip solutions require specialized antenna design, depending on the device. Antenna design requires specialized skills to ensure that the Bluetooth radio will operate within its specification.

Bluetooth Radio and Baseband: The Bluetooth radio is the hardware transceiver unit that implements the Bluetooth radio specification. The purpose of the specification is to provide compatibility between Bluetooth devices that operate in the 2.4 GHz ISM band, and to define the quality of the system. Further information on the Bluetooth radio specifications may be found in the Bluetooth core specification document.

The Bluetooth baseband consists mainly of a Link Controller (LC) that carries out baseband protocols and low-layer link routines. Protocols defined within the scope of the baseband specification include (among others) physical channels and links, data packet definitions, error correction and detection, logical channels, channel control, and hop selection. For more information about the Bluetooth baseband specification, see the Bluetooth core specification document.

An example implementation of the Bluetooth radio and baseband is the Ericsson Bluetooth Module. In addition to the hardware, this module contains the firmware that implements the baseband specifications. As you'd expect, there are a number of other manufacturers developing Bluetooth modules too.

Bluetooth Software Protocol Stack: The Bluetooth software protocol stack can be thought of as driver code. This code allows the application software to send and receive information from the Bluetooth module. Several implementations of this currently exist, and vary from GNU licensed code to commercial products targeted at various operating systems.

Major components of the protocol stack are the Link Manager (LM), the Logical Link Control and Adaptation Protocol (L2CAP), the Host Control Interface (HCI), the Service Discovery Protocol (SDP), Audio/Telephony Control, RFCOMM, Human Interface Device (HID), TCP/IP, and other high level protocols.

Link Manager (LM): The LM manages link setup, link configuration, and link packet control and transfer. The LM also manages link security during the initialization of the connection and throughout its existence (where applicable). The LM handles synchronous and asynchronous packet communication within the piconet, as well as the timing parameters used during communication. The LM also handles master/slave role switching between devices. Sniff, hold, and park mode behavior is controlled by the LM too.

'Sniff', 'hold', and 'park' are power saving modes in which a Bluetooth device may operate. They allow for varying levels of participation and communication within a piconet. The use of each of these modes is broadly determined by the type of device, its function, and overall need for immediate service.

Logical Link Control and Adaptation Protocol (L2CAP): The services provided by L2CAP include protocol multiplexing, segmentation and reassembly, and quality of service. The L2CAP protocol architecture is connection-oriented, with connections labeled by a channel identifier. Each channel is assumed to be a full-duplex connection, with a Quality-of-Service (QoS) flow specification being applied to each channel direction.

Protocol multiplexing enables an application to use several higher-layer protocols simultaneously - RFCOMM, TCP/IP, etc. This service also passes packets used by the higher layer protocols to the appropriate handlers. Protocol identifiers have a one-to-many mapping with channel identifiers. For example, a master device may provide a TCP/IP service and have more than one slave unit using that service.

Segmentation and reassembly is a service by which packets from higher layer protocols are segmented into appropriate-sized Bluetooth packets and reassembled again after transmission. This service is transparent to the higher layer protocols.

The L2CAP also negotiates and enforces Quality Of Service (QoS) contracts, which are based on the type of service provided, with a 'best effort' contract used by default. QoS regulates the token size (bytes), the rate and peak bandwidth (bytes/sec), and other key elements to ensure a robust connection.

Host Control Interface (HCI): The HCI provides a standard interface to the Bluetooth module and link manager services that is independent from the host hardware implementation. This layer provides transparency between the host controller and the Bluetooth hardware. There is an addendum to the HCI specification for each physical bus (USB, PCI, RS232, etc.) that further defines the interface functions based on which physical bus is used.

Service Discovery Protocol (SDP): The SDP is the layer that exposes high-level services such as LAN access or printer services to users and other applications. This layer also provides information to implement a plug-and-play solution, such as a laptop computer using a printer. This layer could be implemented using a higher SDP such as Java JINI.

Audio and Telephony Control: These two protocols are linked, because in the Bluetooth specification, telephony Control contains Call Control and Audio Control. This protocol defines the interface needed to connect and disconnect a call, including signaling the devices desired to participate in the connection. Telephony audio links are established with synchronous links, and therefore do not go through the same L2CAP-to-LM path that asynchronous links go through. Audio links may be thought of as direct baseband to baseband links.

RFCOMM: RFCOMM provides a protocol to emulate cables with Bluetooth, enabling compatibility with a large base of applications that currently use the serial port as their main communication bus. RFCOMM conveys all of the RS232 control signals, and supports remote port configuration. RFCOMM borrows from the IrComm in the IrDA protocol stack.

Human Interface Device (HID): HID is a protocol that enables the concept of a cordless computer. HID describes keyboards, mice and joysticks. This layer would enable plug and play support for such devices when used with a PC.

TCP/IP: TCP/IP over Bluetooth presents a powerful way to link devices. TCP/IP is a network and transport layer that's widely supported by applications and APIs across almost every operating system. The problems with using TCP/IP over Bluetooth include, among others, handling ad hoc networking, DNS name resolution, and broadcasting. Better profiles for networking with Bluetooth are currently being developed by the SIG.

Other Protocols: Other protocols include things such as WAP, object exchange, still image, IR, etc. These protocols would be used by an application that sends its native packets through Bluetooth, just as it would use any other transport layer. All of these possibilities exist within the scope of Bluetooth. All that is missing is the development of the applications.

Bluetooth Chip Manufacturers
Bluetooth chips are being manufactured by the likes of VLSI, owned since June 2nd 1999 by Philips. In October 1999, Motorola acquired Digianswer, an early Bluetooth adopter, to boost its Bluetooth and HomeRF portfolio. VLSI has supplied Bluetooth chips to Ericsson for its wirefree Headset reviewed below Lucent Technologies Microelectronics Group (see below), Cambridge Silicon Radio (CSR) and others also manufacture Bluetooth chip solutions.

Ericsson Bluetooth Headset
Ericsson has unveiled the Bluetooth Headset (available on the market in mid 2000), a headset that connects to a mobile phone by a radio link instead of a cable. It is the first ever handsfree accessory to incorporate Bluetooth technology, the future industry standard for wireless communication between devices. The Ericsson Bluetooth Headset is a lightweight, wireless mobile phone headset, with a built-in Bluetooth radio chip that acts as a connector between the headset and the Bluetooth plug on the Ericsson phone. Weighing 20 grams (0.75 oz.), the Bluetooth Headset sits comfortably on either ear and can be used with Ericsson T28, T28 WORLD and R320 cellular phones.

Lucent Technologies
Lucent Technologies Microelectronics Group has announced its first integrated Bluetooth chipset solution, designed to enable wireless information sharing between personal communications devices and speed end products to market through simplified development and certification. Lucent's new solution consists of a single-chip radio subsystem and a baseband controller, complete with protocol software. The W7400 is available with a Lucent-supplied software protocol stack. Samples and development tools for the W7400 will be available in March 2000, with production starting in 3Q 2000.

Interference Issue
Possible interference between different wireless data standards that do not require federal licensing agreements could delay Bluetooth products from coming to market. According to Cahners Business Information, the 2.4-GHz radio frequency broadcast on an Industrial and Scientific Network, or ISN, already carries traffic from various industrial communication devices and Bluetooth signals could interfere with ISN traffic.

There are also concerns about use of Bluetooth on airplanes. While cell phones and pagers are usually turned off in flight, Bluetooth has been designed to maintain uninterrupted connections even while in motion, while the devices are still in their carrying cases, or even if the devices aren't turned on.