- A Technology and a Standard
- A Technology and a Standard
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1.0 Introduction
This site was undertaken as a final year project at the University of Plymouth by myself, Steven Bush, and was carried out under the supervision of Richard Linford. The site was designed specifically to aid those interested in learning about the Bluetooth technology and standard. It covers the most prominent points of Bluetooth including how and why it works, practical uses for the technology, major advantages over similar technologies and a host of other useful information.
Provided at the end of each section will be optional questions to see whether you have learnt anything interesting about the technology. Simply rest your cursor on the graphic where it says "Question 1 or 2" to display a question!
To make navigation of this site easier, clicking on any hyperlinks will navigate to the relevant URL within this same window. To return, simply press the back button on your internet browser. If any terms are unclear, go to the glossary for a more detailed description or carry out a search on the internet.
Finally, clicking here will open a complete map of this website. Clicking on any of the links will take you directly to the corresponding section. Alternatively, click on one of the chapter links on the control panel above to the left to jump to that section. Click on the "Back to Top" buttons throughout this page to return to the top.
Harold Bluetooth was a Viking chief who lived during the 10th Century as the King of Norway and Denmark. Contrary to popular opinion, Bluetooth or "Blåtand" (as known in old Viking language) had nothing to do with blue teeth; it meant dark complexion. Harold physically fit the classic Viking image. During his reign, he waged war against Germany and managed to accumulate a huge armada of Viking ships, whose crews almost overran northern Germany. Harold Bluetooth converted many Germans to Christianity but ultimately; he was overthrown and died in exile.
In 1994, Ericsson created the first concept of the technology that was later to become Bluetooth. First, they carried out a study to find a low power and low cost radio interface between mobile phones and other accessories. Requirements regarding price, capacity and size were set so that the new technology would have greater potential than cable solutions between mobile devices.
Initially a suitable radio interface with a corresponding frequency range had to be specified. A number of criteria for the concept were defined regarding size, capacity and number of other features. The radio unit was to be small enough and consume such low power that it could be fitted into portable devices. The concept also had to be able to handle both speech and data and as a result, Bluetooth was born.
Much of Harold’s history was learnt from two runic stones, erected in his memory in Jelling, Denmark. In Sweden 1994, In tribute, Ericsson erected a third runic stone to the memory of Harold Bluetooth who gave his name to a new wireless technology for mobile communications. In 1994, nine major telecommunications companies joined to form the Bluetooth SIG (Special Interest Group) consisting of 3COM, Ericsson, Intel, IBM, Lucent, Microsoft, Nokia, Toshiba and Motorola. Since then, thousands of companies have joined the SIG to work towards an open standard for the Bluetooth concept.
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3.0 …So What Exactly is Bluetooth?
Bluetooth is a new technology and standard, launched in 1998. It is essentially, a small microchip which uses a short-range radio link to exchange information, enabling wireless connectivity between mobile phones, mobile PCs and other peripherals. When two Bluetooth enabled products come within 10 metres of each other, they will automatically connect and synchronize. Because the technology uses a short-range radio link, it means that
line of sight is not required for it to function. Using this new technology, it will soon be possible to send a print command from your computer to the printer in the next room, via radio link directly through the wall!Bluetooth offers 3 major advantages:
Voice/Data access point:
Voice: 3 simultaneous voice channels are used, or a channel which simultaneously supports asynchronous data and synchronous voice. Each voice channel supports a 64kb/s synchronous (voice) channel in each direction.
Data: The asynchronous data channel can support maximal 723.2 kb/s asymmetric (+56kb/s in the return direction), or 433.9 kb/s symmetric.
It acts as a cable replacement!
Bluetooth wireless technology eliminates the need for numerous wired connections to other devices. Connections are instant and are maintained even if the devices do not have a clear line of sight. The range of each Bluetooth enabled device is around 10 metres but optionally reaches distances of up to 100 metres with an amplifier.
Allows the user to create ad-hoc networks:
A Bluetooth enabled device establishes a connection to another Bluetooth enabled device as they come within 10 metres of each other. Bluetooth enabled products support both point-to-point and point to multi-point connections, therefore, several piconets can be established and linked ad hoc.
4.0 Bluetooth - A Brief Overview The Bluetooth System:
Operates in the 2.4 GHz ISM (Industrial Scientific Medicine) band
Has a range of 10 - 100m range (0 - 20dBm)
Uses a Frequency Hop (FM) spread spectrum, which divides the frequency band into a number of hop channels
During connection, radio transceivers hop from one channel to another (1600 hops/s)
Supports 8 devices in a Piconet
Has in built security and uses an error detection and correction technique called ARQ
Utilises non line-of-sight transmission through walls, briefcases and any other mediums and is omni-directional
Is regulated by governments worldwide
Uses 1mW of power during normal transmission (-30 to +20 dBm is optional)
Can operate in 2 modes - Circuit switched (common for voice communications) and Packet switched (used for Internet data and higher bandwidth communication systems)
Is low cost!
4.1 Frequency Hopping
Frequency hopping means that the Bluetooth technology transmits and receives on 79 hop frequencies from 2402 to 2480 Mhz, hopping in a pseudo random sequence, 1600 times a second. The technology uses Gaussian frequency shift keying modulation with the maximum data rate of 721 Kbps. A complete Bluetooth protocol stack has been developed as well as imported layers such as TCP/IP.
Interference is avoided by using a frequency-hop (FH) spread spectrum technology. This technology is suited for low-power, low-cost radio implementations and is used in some wireless LAN products. The main advantage with Bluetooth’s transmission is the high hop rate of 1600 hops per second. Bluetooth also uses a short packet length, which is another benefit.
The ISM frequency band is divided into a number of hop channels. Every hop channel is just a fraction of the total frequency band. In Bluetooth one channel is used every 625 microseconds (one slot) followed by a hop in a pseudo-random order to another channel for another 625 microseconds. In this way the hopping spreads the Bluetooth traffic over the entire ISM band and good protection from interference is achieved. If one of the transmissions is interrupted for whatever reason, the probability of interference on the next hop channel is very low. Multi-slot packets can be sent over up three or five 625 microsecond slots but the packets are always sent on the same hop channel. Error correction algorithms are used to correct the fault caused by jammed transmissions.
4.2 Bluetooth Packet Format
The Bluetooth packets have a fixed format. A 72-bit access code comes first in the packet. The access code is based on the master's identity and the master's system clock. It provides the means for synchronisation. This code is unique for the channel and is used by all packets transmitting on the same specific channel.
A 54-bit header follows the access code. This header contains error correction, retransmission and flow control information. The error correction information can be used for correcting faults in the payload and in the header itself. Finally comes the payload containing anything between 0 and 2,745 bits.
5.0 Practical Uses for Bluetooth
The possibilities for Bluetooth are huge; below are a number of uses for the new technology:
When arriving home, your PDA (Personal Digital Assistant) synchronizes with your house and the front door unlocks, preferential lighting comes on and any other pre-set configurations become active.
You arrive at the cinema/theatre to find a long line at the ticket desk. Using your PDA, you confirm and pay for the tickets via wireless link, avoid the line and take your seat (after grabbing some popcorn!).
Approaching your car, the door unlocks, the radio tunes itself to your preferred station and preset preferences become active.
As you enter your home, your PDA configuration changes from any preset business settings to home settings. Business appointments and schedules are added to the electronic calendar.
When upgrading systems and adding devices (security for example) because all products are Bluetooth enabled, they will automatically reconfigure and recognize each other.
As you arrive at the reception of your hotel, you are automatically checked in. Your room number and electronic key are transferred to your PDA. As you approach your room, you will be able to unlock the door via your PDA.
You arrive at the office and your PDA automatically synchronizes with the Desktop PC and transfers any new files, e-mails and schedule Information.
While in a meeting, you can transfer any presentations from your PDA to the main display. Meetings can be recorded on your PDA, which can then be transferred to the attendants of the meeting before they leave.
A small California company said this week that it has it has developed the technology that uses Bluetooth networks in which users can exchange text messages.
Inventop Software has developed something called ProximityMail which uses Bluetooth to create a spontaneous "Relay Area Network" (RAN) in which users can exchange text messages via PDA’s without the e-mail addresses of mobile phone numbers within ad-hoc networks.
"Our vision is that PDA’s will become a powerful communication tool in the very near future," said Virginie Glaenzer, the company's CEO.
The company said the only requirement is that users must have the ProximityMail application installed on their devices. They also reported that several other companies had agreed to integrate the technology into their products. The company did not say when the technology would be widely available.
(See Reference 1 for more details)
5.2 Five Blue Teeth
Research firm In-Stat has been looking at hardware and software Bluetooth products from several companies from a user perspective; 3Com, Motorola and Red-M proved to excel.
Given that the issues of interoperability, functionality, and user applications are important for the Bluetooth market, In-Stat recently evaluated and rated Bluetooth products by 3Com, Anycom, Compaq, Ericsson, Hewlett-Packard, Motorola, Palm, Pico Communications, Red-M, TDK Systems and Troy Wireless.
The evaluations were conducted and viewed from a users' perspective by installing Bluetooth hardware and software, using various functions that the products would be expected to perform, and considering how well they worked with other Bluetooth devices. Three products were given the highest rating of five blue teeth (good to excellent user experience without set up difficulties and supported functions working easily). These Products included the 3Com PC card and adapter, the Motorola Bluetooth wireless headset and the Red-M 1000AP access points w/3000AS server. "Overall, most of the products tested offered positive user experiences," said Joyce Putscher, director of In-Stat/MDR's Converging Markets and Technologies Group.
In-Stat predicts that the products that will take the market by storm will offer a simple, familiar, intuitive user interface, quick and easy setup, combined with chat, printing, and additional applications that consumers find compelling, productive, and fun. The study also found that for some products, such as the HP 995c printer, 3Com PC Card/USB adapter, and Palm m500/505 with Bluetooth SD card, excellent positive user experiences are virtually guaranteed for the general consumer public.
(See Reference 15 for more details)
6.0 Piconets and Scatternets
When such an ad-hoc Bluetooth network is established a 'piconet' is formed - it can be fixed or provisional. The unit that establishes the piconet becomes the master unit and the rest of the other units, act as slaves. Up to eight active units can form a piconet (within a radius of 10 meters), which is defined by the channel these units share. In a piconet, the master seeks the devices in its entourage by sending out broadcasting requests. The slave answers with its identification number.
As many as 10 Piconets can overlap to form a Scatternet, linking up to 80 Bluetooth appliances. Beyond this, the network saturates. The number of devices in a piconet is actually unlimited even though only eight devices can be active at any given moment. 79 transmission channels are employed by the Bluetooth protocol, a limit based on the frequency.
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