The Bluetooth Wireless Technology

Harald Bluetooth was a Viking and king of Denmark between 940 and 981. One of his skills was to make people talk to each other, and during his rule Denmark and Norway were Christianized and united. 
    Today Bluetooth wireless technology enables people to talk to each other, but this time by means of a low-cost short-range radio link..

   In the Danish town of Jelling Harald Bluetooth raised an enormous rune stone which still stands in its original position. It has the following runic inscription, adorned with an image of Christ: ãKing Harald raised this monument to the memory of Gorm his father and Thyre his mother, that (same) Harald which won all Denmark and Norway and made the Danes Christian.ä Originally the stone was painted. 
    In September 1999 a new stone was raised outside of Ericsson Mobile Communications in Lund, this time to the memory of Harald Bluetooth

The idea that resulted in the Bluetooth wireless technology was born in 1994 when Ericsson Mobile Communications decided to investigate the feasibility of a low-power, low-cost radio interface between mobile phones and their accessories. The idea was that a small radio built into both the cellular telephone and the laptop would replace the cumbersome cable used today to connect the two devices. 
    A year later the engineering work began and the true potential of the technology began to crystallize. But beyond unleashing devices by replacing cables, the radio technology showed possibilities to become a universal bridge to existing data networks, a peripheral interface, and a mechanism to form small private ad hoc groupings of connected devices away from fixed network infrastructures.

The SIG     

In February 1998 the Special Interest Group (SIG) was formed. Today the Bluetooth SIG includes promoter companies 3Com, Ericsson, IBM, Intel, Lucent, Microsoft, Motorola, Nokia and Toshiba, and thousands of Adopter/Associate member companies. The assignment of the SIG originally was to monitor the technical development of short range radio and to create an open global standard, thus preventing the technology from becoming the property of a single company. This work resulted in the release of the first Bluetooth Specification in July 1999. The further development of the Specification still is one of the main issues for the SIG, other important tasks are interoperability require-ments, frequency band harmonization and promotion of the technology. Learn more about the Bluetooth SIG at http://www.bluetooth.com/ 

Interoperability    

From the very start one of the main goals for the SIG has been to include a regulatory framework in the Specification that will guarantee full interoperability between different devices from various manufacturers - as long as they share the same Profile. While the usage models describe applications and intended devices, the Profiles specify how to use the Bluetooth protocol stack for an interoperable solution. In each Profile it is stated how to reduce options and set parameters in the base standard, how to use procedures from several base standards. A common user experience is also defined. For exam-ple, a computer mouse doesnât need to communicate with a headset, and so they are built to comply with different profiles. The Profiles are a part of the Bluetooth Specification, and all devices must be tested against one or more of the Profiles in order to fulfil the Bluetooth certification requirements. The number of Profiles will continue to grow as new Bluetooth applications arise.

Bluetooth Products    

Many companies have declared that Bluetooth wireless technology will be incorporated into their products, especially when components becomes cheaper. In a forecast made by Cahners In-Stat Group (July 2000), the product availability during the next couple of years was defined as three waves. 
    

The first wave is believed to occur around the turn of the year 2000/2001 and will include products like: 

• Adapters for mobile phones and adapters (dongles) and PC Cards for notebooks and PCs 

• High-end mobile phones and notebook PCs with integrated Bluetooth communication for the business users. 

• Bluetooth headsets are expected to enter the market by the first half of 2001. 

• Cordless phones, handheld PCs, and PDAs will also be included in this first wave. The first handheld PCs and PDAs are expected to enter the market during 2001. 

     The second wave will in many respects overlap the first. What we will see here is: 

• PCs with Bluetooth circuitry on the motherboard. 
• Printers, fax machines, digital still cameras, and products for industrial/medical and verti-cal industries will also begin to move in the second wave.
• There will be some industrial solutions that may become available as soon as the end of 2000 or 1Q2001. 
• In the automotive sector the first Bluetooth options are expected to appear for the 2002 model year (hands-free mobile phone usage with your regular mobile phone) 

     The third wave will include 

• Low-cost mobile phones and lower-cost portable devices and desktop PCs.

     Especially after the first wave is completed the cost and development time of e-menu will decrease enormously since we will not need to use the bluetooth hardware seperately. At the time that is market is ready for bluetooth and PDA applications, Crein will be there.

In phase with the IT-boom the mobility among people has constantly grown and wireless technologies for voice and data have evolved rapidly during the past years. Countless electronic devices for home, personal and business use have been presented to the market during recent years but no widespread technology to address the needs of connecting personal devices in Personal Area Networks (PAN). The demand for a system easily could easily connect devices for transfer of data and voice over a short distances - cables, grew stronger. The Bluetooth wireless technology fill this important communication need, with its ability to communicate both voice and data wirelessly, using a standard low-power, low-cost technology which can be integrated in all devices and thus enable total mobility. The price will be low and result in mass production. The more units around, the more benefits for the customers. 

The Technology    

The Bluetooth Specification defines a short (around 10 m) or optionally a medium range (around 100 m) radio link capable of voice or data transmission to a maximum capacity of 720 kbps per channel. 

    Radio frequency operation is in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.48 GHz, using a spread spectrum, frequency hopping, full-duplex signal at up to 1600 hops/sec. The signal hops among 79 frequencies at 1 MHz intervals to give a high degree of interference immunity. RF output is specified as 0 dBm (1 mW) in the 10m-range version and -30 to +20 dBm (100 mW) in the longer range version. 

    When producing the radio specification, high emphasis was put on making a design enabling single-chip implementation in CMOS circuits, thereby reducing cost, power consumption and the chip size required for implementation in mobile devices. 
    Voice 
    Up to three simultaneous synchronous voice channels are used, or a channel which simul-taneously supports asynchronous data and synchronous voice. Each voice channel sup-ports a 64 kb/s synchronous (voice) channel in each direction. 
    Data 
    The asynchronous data channel can support maximal 723.2 kb/s asymmetric (and still up to 57.6 kb/s in the return direction), or 433.9 kb/s symmetric. 

• A Master can share an asynchronous channel with up to 7 simultaneously active slaves in a Piconet. 

• By swapping active and parked slaves out respectively in the piconet, 255 slaves can be virtually connected using the PM_ADDR (a device can participate again within 2 ms). 
• To park even more slaves the BD_ADDR can be used. There is no limitation to the number of slaves that can be parked. 

Slaves can participate in different piconets and a master of one Piconet can be the slave in another, this is known as a Scatternet. Up to 10 piconets within range can form a Scatternet, with a minimum of collisions.

 

Bluetooth units that come within range of each other can set up ad hoc point-to-point and/or point-to-multipoint connections. Units can dynamically be added or disconnected to the network. Two or more Bluetooth units that share a channel form a piconet. 
    Several piconets can be established and linked together in ad hoc scatternets to allow communication and data exchange in flexible configurations. If several other piconets are within range they each work independently and each have access to full bandwidth. Each piconet is established by a different frequency hopping channel. All users participating on the same piconet are synchronized to this channel. Unlike infrared devices, Bluetooth units are not limited to line-of-sight communication.
    To regulate traffic on the channel, one of the participating units becomes a master of the piconet, while all other units become slaves.With the current Bluetooth Specification up to seven slaves can actively communicate with one master. However, there can be almost an unlimited number of units virtually attached to a master being able to start communication instantly.

The Bluetooth hardware consists of an analog radio part and a digital part - the Host Con-troller. The Host Controller has a hardware digital signal processing part called the 
     Link Controller (LC), a CPU core and interfaces to the host environment. The Link Controller consists of hardware that performs baseband processing and physical layer protocols such as ARQ-protocol and FEC coding. The function of the Link Controller includes Asynchronous transfers, Synchronous transfers, Audio coding and Encryption. 
     The CPU core allows the Bluetooth module to handle Inquiries and filter Page requests without involving the host device. The Host Controller can be programmed to answer cer-tain Page messages and authenticate remote links. 
     The Link Manager (LM) software runs on the CPU core. The LM discovers other LMs and communicates with them via the Link Manager Protocol (LMP) to perform its service provider role and to use the services of the underlying Link Controller. Ericsson offers complete packages of intellectual property (IP) that support both Bluetooth core and Bluetooth radio chip development.

Below, you can see the current and estimated hardware evolution. 

The Bluetooth protocols are marked with blue color in the illustration below. In order to make different hardware implementations compatible, Bluetooth devices use the Host Controller Interface (HCI) as a common interface between the Bluetooth host (e.g. a por-table PC) and the Bluetooth core. 
     Higher level protocols like the Service Discovery Protocol (SDP), RFCOMM (emulating a serial port connection) and the Telephony Control protocol (TCS) are interfaced to baseband services via the Logical Link Control and Adaptation Protocol (L2CAP). Among the issues L2CAP takes care of, is segmentation and reassembly to allow larger data packets to be carried over a Bluetooth baseband connection. 
     The service discovery protocol allows applications to find out about available services and their characteristics when e.g. devices are moved or switched off. 
     Crein currently uses a generic software that includes HCI Driver, L2CAP, RFCOMM and SDP to be integrated in a host environment by Ericsson.