Bluetooth is an open standard for speech and data transmission. Besides the applications for this new technology, e. g. the wireless connection between mobile station and terminal equipment, also the structure of the Bluetooth system architecture is presented. The set-up of so-called short-range ad hoc networks (piconets and scatternets) will be introduced. Bluetooth wireless technology is an open, accepted standard for wireless communication which means that Bluetooth electronic equipment can communicate as long as they are within approx.
10 meters of each other, making it possible to transfer data, speech, music or images without a physical connection. The mobile telephone manufacturer Ericsson invented Bluetooth technology, naming it after the Viking King Harald Bluetooth. Just as King Harald Bluetooth united Denmark and Norway, Bluetooth technology “unites” various types of electronic equipment to form a coherent whole. Ericsson formed the foundation for Bluetooth as early as 1994, but the standard was not ready for use until 1998. The first Bluetooth products came on the market in 2000.
Today, Bluetooth technology can be found in all types of electronic equipment – including mobile phones, mobile headsets, PCs, keyboards, mouse devices, printers, GPS navigation units, video cameras and pocket PCs – and new products are emerging every day. Today, Bluetooth technology is an essential everyday tool to be found in a variety of electronic equipment. The technology makes it easy to transfer speech between a mobile phone and a headset, a mobile phone and a pocket computer or images from a digital video camera to a PC.
Even though two Bluetooth units can find each other and be connected, because they both comply with the standard, it may not necessarily make sense for them to speak to each other. For instance, a Bluetooth mouse would not profit much from a connection with a digital camera, or a headset with a keyboard. The basic requirement for Bluetooth units to be able to communicate is that they are located within 10 meters of each other. That is the range of the Bluetooth radio waves – at least under the current standard.
The study intents to (1) know the key features of Bluetooth technology; (2) evaluate Bluetooth Special Interest Group (SIG) and its key role in maintaining specifications of the protocol, profiles, testing and qualification, interoperability and compatibility and; (3) how Bluetooth applies to wireless technology. II. Background As Bluetooth technology becomes more common, however, we will undoubtedly see CD players that send sound to amplifiers via Bluetooth, which then transfer the sound to speakers in the same way.
A Bluetooth enabled pocket computer will automatically synchronise with a company’s diary and make sure that the day’s e-mails are ready to be read on the screen. And car radios will turn the music down and transfer the speech from a mobile phone when it rings (see “Bluetooth”. New Standard Encyclopedia, pp. 36-38). Moreover, the Bluetooth brand is now recognized worldwide on products with short range wireless communication capabilities. The brand is a label that is not a single company technology but is shared by many members of the Bluetooth SIG.
The brand is applied to devices implementing the Bluetooth technology; even if it says little about the way the technology works (see “Bluetooth”. New Standard Encyclopedia, pp. 36-38). III. Discussion A. Features of Bluetooth Technology The logo for Bluetooth is based on Runes surrounding the legend of Harald Bluetooth. Bluetooth the technology is based on communications central to man’s own personal space. Fundamentally Bluetooth operates within the Industrial, Scientific and Medical (ISM) band at 2. 4 GHz.
It is a short-range wireless communication standard defined as cable replacement for a Personal Area Network (PAN) (see “Bluetooth”. Grolier Encyclopedia of Knowledge, pp. 87-94). Figure 1 is the Bluetooth Logo. A cable replacement standard has been defined because cables limit mobility of the consumer; they are cumbersome to carry around, are easily lost or broken. Often connectors are prone to difficult to diagnose failures; or are proprietary. To counteract these limitations Bluetooth is designed to be light and portable. It can be embedded to take the riggers of physical knocks and shocks.
It includes standards and protocols to make it mobile, robust, reliable and not limited to one manufacturer (see “Bluetooth”. Grolier Encyclopedia of Knowledge, pp. 87-94). The operating band also fits the goals of Bluetooth, imposing requirements as a cable replacement. The cost needs to be comparable with cable. Reductions can be achieved by operating in the licence free 2. 4 GHz ISM band, keeping backward compatibility wherever possible lowers the cost of ownership by avoiding upgrades and having a relaxed radio specification enables single chip integrated circuit solutions.
It also needs to be as reliable and resilient as cable and cope with errors and degradation caused by interference. For mobile devices it must be compact, lightweight, low power and easy to use (see “Bluetooth”. Grolier Encyclopedia of Knowledge, pp. 87-94). A. 1 Frequency Hopping We have addressed the reasons for the Bluetooth without delving into the ‘nuts and bolts’ of the technology to discover how it operates. For the majority of countries the ISM band used by Bluetooth is available from 2. 40-2. 4835 GHz, although some countries impose restrictions.
In this band Bluetooth uses Frequency Hopping Spread Spectrum (FHSS) techniques in order to improve its immunity from interference (see J. Bray and C. F. Sturman, Bluetooth: Connect Without Cables”, Prentice Hall). In unrestricted countries the radios hop in pseudo random sequences around all available channels, this equates to 79 RF channels with a channel spacing of 1 MHz. Starting at a base frequency of 2402 MHz then the frequency of the channels, f, can be expressed as: f =2402 + n MHz where, n, is the channel number with an integer value in the range of 0 to 78.
In restricted countries a limited frequency hopping schemes with just 23 channels is used and is catered for in the Bluetooth specification. Both hopping schemes have a 1 MHz channel spacing making it possible to design a simple radio interface whereby the baseband only has to specify a channel number and the radio multiplies this up to the appropriate frequency offset (see J. Bray and C. F. Sturman, Bluetooth: Connect Without Cables”, Prentice Hall). In this FHSS scheme there are 1600 hops per second, which is a hop every 625 µs.
Part of this hop timing is taken up by the guard time of 220 µs allowing the synthesizer time to settle. The frequency hopping implements time division multiplexing as shown in Figure 2. The basis of the scheme has the Master device transmitting in the first 625 us slot, k, and here the Slave receives. In the next slot k = 1 the Slave is permitted to transmit and the master listens (see J. Bray and C. F. Sturman, Bluetooth: Connect Without Cables”, Prentice Hall). Figure 2: Frequency Hopping, master and slave interact on corresponding slots
The radio must be able to retune and stabilise on a new frequency within tight time constraints. This is pushed further when establishing a connection; the hop rate can be shortened to every 312. 5 us. As the radios are constantly hopping to different radio channels, this ensures that packets affected by interference on one channel can be retransmitted on a different frequency channel. To further enhance resilience both ARQ (Automatic Repeat reQuest) and FEC (Forward Error Correction) form part of the specification (see J. Bray and C. F. Sturman, Bluetooth: Connect Without Cables”, Prentice Hall).
One drawback with the normal hop sequence is the time taken for production testing. Bluetooth ensures adequate frequency coverage with a test sequence allowing the radios to be tested at a faster rate (see J. Bray and C. F. Sturman, Bluetooth: Connect Without Cables”, Prentice Hall). A. 2 The Bluetooth SIG and Specifications If the success of Bluetooth is measured by its initial interest alone then its prominence has already been assured. Before products were on sale, hundreds of companies joined the Bluetooth Special Interest Group (SIG) and the Bluetooth brand became recognized worldwide.
Before investigating the technology further it is appropriate to comment about the role played by the SIG, the administrative structure of which is outlined in Figure 3. With membership of the SIG nearing 2500 members it is only right to look at how the SIG works to promote, shape and define the specification and position Bluetooth in the market place. Positioning of the technology is important when you consider other wireless technologies that share the same ISM band, e. g. IEEE802. 11b, HomeRF and DECT. Differentiation is key in avoiding confusion of potential users.