Bluetooth is the wireless wave of the present and future. It promises low power, high speed data transmission over small areas with little or no interference. Many people think the name Bluetooth and Bluetooth Headset for mobile phones are synonymous. A big reason Bluetooth came about was to rid the world of wired technologies where wires aren’t desired. Bluetooth headsets are one of the endless possibilities of Bluetooth. From wireless USB to wireless Headphones to wireless Data Synchonization to short range gaming, Bluetooth can do it all.

Old History From 940 to 985 AD there lived a king named Harald I Bluetooth who ruled over Denmark. Bluetooths brother in-law was killed by a ruthless Norwegian king. Bluetooths sister then asked for Bluetooth to conquer Norway for taking her husbands life. He eventually ruled over Denmark and Norway. He made the Danes Christians and united Scandanavia in time of war₁.

New History Just as Harald Bluetooth united the war torn region, Bluetooth would unite the world of computers and telecommunications wirelessly. Bluetooth was first initiated by the Swedish company Ericcson in 1994 ₂. In 1998, after a few years of research and development into the cable-less technology five companies including, Ericsson, Nokia, IBM, Toshiba, and Intel formed the Bluetooth SIG (special interest group)₂. In 2003, the SIG announced its first major update to the initial release of Bluetooth, Bluetooth version 1.2. In 2005, devices using Bluetooth 2.0 + Enhanced Data Rate were put into the market ₂.

The Bluetooth logo was originally designed by a Scandinavian firm in 1998. In Runic letters it represents the H and B, the initials of Harald I Bluetooth, combined ₂. See figure below. ₉

Bluetooth transmits its information at a frequency of 2.45 GHz₅. The frequency is located on the ISM operating band which is reserved for Industrial, Scientific, and Medical unlicenced signals. It is a non-commercial band₆. Bluetooth signals could possibly interfere with other devices on the same band if they were more powerful. But the signals are only 1 milliwatt compared to the most powerful devices on the same band capable of transmitting 3 watts₅. ₅

Bluetooth data packets have a standard format. The Access Code, the Header, the Payload, and the Inter-Packet Guard Band. The access code is used to initate the communication. The header gives tag information about the data. The Inter-Packet Guard Band avoids collisions and re-tunes the receiver. Gaussian Frequency Shift Keying is used to transmit the Access Code and Header. Mandatory Modulation transmits the actual payload(the majority of the data being sent)₇. A typical Gaussian Frequency Shift Keying transceiver modulates a signal into a RF signal, and demodulates the signal to digital₈. Mandatory Modulation is the process of using 4 differential phases in phase shifting. Versions prior to Bluetooth 2.0 only used frequency modulation. Mandatory Modulation allows for a faster transmission of data, as phase shifting usually does₇.

Within the Bluetooth SIG is a Bluetooth Security Experts Group. As new versions of Bluetooth come out, the security group is testing them for any threats and doing whatever they can to combat them. Bluetooth uses a pairing process to establish a secure connection and then uses an encryption algorithm to maintain the secure connection₄. Bluetooth vendors have the option to choose from three different security levels:

1. Non-secure
2. Service level enforced security – The connection is established and then asked for a PIN when a service is trying to be used.
3. Link level enforced security – The connection is not established until the correct PIN is entered to pair the device

On the next page you will see how the security process takes place through the process of pairing.

In order for two Bluetooth device to communicate they must be logically connected. In order for a device to be discovered and connected to by another, it must be in what is called discoverable mode. If it is in non-discoverable mode it can not be seen unless very powerful developer’s hardware is used. Non-discoverable devices can still make requests for connections with other discoverable devices. The process of pairing is as follows:_11,12

1. The First step in making a connection to another Bluetooth enabled discoverable device is to send out an Inquiry.
2. The initial device sends out a series of inquiry packets waiting for an inquiry reply from whatever devices are in range. If the device is in the inquiry scan state(discoverable mode) then it reads the inquiry packets.
3. After reading the inquiry packets, the receiving device may respond with an FHS packet, or Frequency Hopping Synchronization Packet. The FHS packet is a control packet that responds with the Bluetooth physical address and clock of the device.
4. Now that the initial transaction is complete, the paging process can begin, and then the pairing process if needed.
5. Now that the initial device has a list of all available devices in the surrounding area, the initial device can make an actual connection to one or more of them.
6. The source device sends a page to the destination, the destination receives the page, and sends a reply to the source.
7. The source then sends a FHS packet to the destination and the destination replys a second time.
8. After the second reply, the two devices switch to the channel that the source is already on. The source/initial device is now the master, and the destination is now the slave device.
9. The connection is maintained by the slave sending dummy packets to the master.
10. When the master wants to pair up, it will send a LMP_host_connection_req and the remote device can accept or reject the request. If the slave accepts the request and enters the correct pairing key then the services of the slave are available to the master.

Below is an animation of the connection process: ₉

The Piconet shown in the above animation is a simple one. The master device of a piconet can have up to 7 slave devices connected to it. The network formed from the connection of 2 or more device is called a piconet. A scatternet can be formed by connecting two or more piconets, allowing certain devices to act as a bridge from one piconet to the other. They do this by playing the role of slave and master at the same time. Each slave in a piconet is accessed one at a time by the master. The master rapidly switches from one slave to the other continuosly(6).

Bluetooth vs. WiFi In certain situations, Bluetooth and WiFi can be considered rival technologies. Although, in most situations they can live in harmony together, each performing its own tasks, doing what each does best. While 'some' PDAs/PDA phones are coming out with WiFi integrated into them, it can be hard to find a PDA or PDA phone without Bluetooth now. There are several reasons why this is.
Bluetooth is more immune to interference due to its Frequency hopping capabilities, thus making it a more viable solution for use in crowded, urban environments₁₃. While both technologies have good voice quality when there is little or no interference, Bluetooth is the only one to stay strong during a time of much interference₁₃. Bluetooth requires much less power than WiFi, enabling it to always be on and discoverable with very little battery degredation. Wifi requires up to 500% more power when actively being used and up to 100% more power when in standby. Bluetooth is also much smarter when conserving its power₁₃. Most Bluetooth devices can be both the master and the slave to any other device that can be a master or slave. WiFi does not have the ability to establish connections on such a peer to peer and personal level that Bluetooth can. While WiFi does not seem to be the most viable mobile solution, it has its place in every office and home. It is up to 18 times faster than Bluetooth.

Bluetooth vs. UWB Ultra-wideband, or UWB, is not nearly as popular as Bluetooth or WiFi technologies yet. Though there is much promise for UWB. ii. UWB offers up to 480 Mbps. That is just as fast as a wired USB connection. It does all of this while using very little power₁₆. UWB can also be used in positioning, using very small sensors, being trackable from miles away₁₅. iv. In 2005 the Bluetooth SIG announced that it would make its Bluetooth devices able to communicate via the UWB interface, and hopefully other wireless interfaces in the future₁₄.

Since 1998 there have been many improvements to the Bluetooth technology with much thanks going to the Bluetooth Special Interests Group. The next version of Bluetooth is due to have even more improvements than the upgrade from 1.2 to 2.0. Atomic Encryption Change will allow encryption keys to be changed on a timed basis and will allow the master and slave role to be reversed₆. Extended Inquiry Response will allow more information to be gathered during the inquiry process of pairing₆. Sniff Subrating will reduce power consumption on mice and keyboards 3 to 10 times greater than current standards₆. Simple pairing is expected to dramatically increase the use of Bluetooth because it will make it a better experience while pairing and strengthening security at the same time₆.

• www.bluetomorrow.com : A simple, very informative site dedicated completely to explaining Bluetooth.
• www.howstuffworks.com : Great tutorials on EVERYTHING along with a few on Bluetooth.
• www.en.wikipedia.org : Endless information, a ton about Bluetooth. Best of all it is updated relatively instantly compared to other sites.
• www.palowireless.com : Site dedicated to all types of Wireless. Good technical data.
• www.bluetooth.com : Informative, some biased, but is kept up to date showing the dedication of the Bluetooth SIG.

Links are numbered corresponding to the subscripts throughout the document.

1. History of Bluetooth
2. Bluetomorrow
3. Bluetooth SIG
4. Wikipedia - Runic Alphabet
5. Howstuffworks - Bluetooth
6. Wikipedia - Bluetooth
7. Bluetooth 2.0
8. GFSK
9. Original Graphics and Animations - Dominic DiCicco
10. Business Engine
11. Bluetooth Glossary
12. Johnson Consulting
13. Commil
14. Bluetooth and UWB integration
15. Ultra-wideband: A Better Bluetooth
16. Wikipedia - Ultra-wideband