What is Bluetooth?

Bluetooth technology eliminates the need for numerous and inconvenient cable attachments for connecting fixed computers, mobile phones, mobile computers, handheld devices, digital cameras and even new breed of digital appliances. It will enable users to connect a wide range of computing and telecommunications devices easily and simply, without the need to buy, carry, or connect cables - quite often proprietary to a specific device. It delivers opportunities for rapid ad hoc connections, and the possibility of automatic, unconscious, connections between devices. It creates the possibility of using mobile data in a variety of applications.

Bluetooth makes wireless communication and networking between devices in a small localized area of a room or a small office as easy as switching on the light. In Bluetooth all the connections between devices are instantaneous and invisible and the devices can talk even if they are not in line of sight because Bluetooth utilizes a radio-based link. Your laptop could send information to a printer in the next room, or your microwave could send a message to your mobile phone telling you that your meal is ready.

Bluetooth is actually a standard for wireless communications between devices in a personal area network (PAN) using radio frequency for a short range (around 10 meters). So any two devices that follow the standard can communicate and exchange data between each other without the need of any connection to be made between them. A group of Bluetooth devices like a mobile phone, a digital camera, a hand held device etc. can instantly form a network with each other as soon as they are switched on. You could have a mobile phone in your pocket and you could be sending e-mails using your laptop without making any connection between your laptop and the mobile. Your refrigerator could be placing an order with the supermarket if your milk supply has been exhausted using your mobile phone.

Briefly, Bluetooth technology

• uses radio waves in 2.4 GHz band - therefore, no line of sight is required
• supports multipoint, not just point to point
• works in a small confined area - 10 to 15 meters apart
• is able to support speeds of 1-2 Mbps today but will offer higher speeds in future
• chip sets are relatively inexpensive (though more expensive than IrDA)- $10 to $20 today in large quantities - will go down in future
• has significant industry support with over 1800 members in the industry consortium

How Bluetooth Technology Works

"Connective convenience"

Bluetooth is a high-speed, low-power microwave wireless link technology, designed to connect phones, laptops, PDAs and other portable equipment together with little or no work by the user. Unlike infra-red, Bluetooth does not require line-of-sight positioning of connected units. The technology uses modifications of existing wireless LAN techniques but is most notable for its small size and low cost. The current prototype circuits are contained on a circuit board 0.9cm square, with a much smaller single chip version in development. The cost of the device is expected to fall very fast, from $20 initially to $5 in a year or two. It is envisioned that Bluetooth will be included within equipment rather than being an optional extra. When one Bluetooth product comes within range of another, (this can be set to between 10cm and 100m) they automatically exchange address and capability details. They can then establish a 1 megabit/s link (up to 2 Mbps in the second generation of the technology) with security and error correction, to use as required. The protocols will handle both voice and data, with a very flexible network topography.

This technology achieves its goal by embedding tiny, inexpensive, short-range transceivers into the electronic devices that are available today. The radio operates on the globally-available unlicensed radio band, 2.45 GHz (meaning there will be no hindrance for international travelers using Bluetooth-enabled equipment.), and supports data speeds of up to 721 Kbps, as well as three voice channels. The bluetooth modules can be either built into electronic devices or used as an adaptor. For instance in a PC they can be built in as a PC card or externally attached via the USB port.

Each device has a unique 48-bit address from the IEEE 802 standard. Connections can be point-to-point or multipoint. The maximum range is 10 meters but can be extended to 100 meters by increasing the power. Bluetooth devices are protected from radio interference by changing their frequencies arbitrarily upto a maximum of 1600 times a second, a technique known as frequency hopping. They also use three different but complimentary error correction schemes. Built-in encryption and verification is provided.

Moreover, Bluetooth devices won't drain precious battery life. The Bluetooth specification targets power consumption of the device from a "hold" mode consuming 30 micro amps to the active transmitting range of 8-30 milliamps (or less than 1/10th of a watt). The radio chip consumers only 0.3mA in standby mode, which is less than 3 % of the power used by a standard mobile phone. The chips also have excellent power-saving features, as they will automatically shift to a low-power mode as soon as traffic volume lessens or stops.

Bluetooth devices are classified according to three different power classes, as shown in the following table.

Power Class	Maximum Output	Power
1	100 mW	(20 dBm)
2	2.5 mW	(4 dBm)
3	1 mW	(0 dBm)

But beyond untethering devices by replacing the cables, Bluetooth radio technology provides 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. Designed to operate in a noisy radio frequency environment, the Bluetooth radio uses a fast acknowledgment and frequency hopping scheme to make the link robust. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving a packet. Compared with other systems operating in the same frequency band, the Bluetooth radio typically hops faster and uses shorter packets. This makes the Bluetooth radio more robust than other systems. Short packages and fast hopping also limit the impact of domestic and professional microwave ovens. Use of Forward Error Correction (FEC) limits the impact of random noise on long-distance links. The encoding is optimized for an uncoordinated environment.

Bluetooth guarantees security at the bit level. Authentication is controlled by the user by using a 128 bit key. Radio signals can be coded with 8 bits or anything upto 128 bits. The Bluetooth radio transmissions will conform to the safety standards required by the countries where the technology will be used with respect to the affects of radio transmissions on the human body. Emissions from Bluetooth enabled devices will be no greater than emissions from industry-standard cordless phones. The Bluetooth module will not interfere or cause harm to public or private telecommunications network.

The Bluetooth baseband protocol is a combination of circuit and packet switching. Slots can be reserved for synchronous packets. Each packet is transmitted in a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots. Bluetooth can support an asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel, which simultaneously supports asynchronous data and synchronous voice. It is thus possible to transfer the date asynchronously whilst at the same time talking synchronously at the same time. Each voice channel supports 64 kb/s synchronous (voice) link. The asynchronous channel can support an asymmetric link of maximally 721 kb/s in either direction while permitting 57.6 kb/s in the return direction, or a 432.6 kb/s symmetric link.

Modes of operation

An interesting aspect of the technology is the instant formation of networks once the bluetooth devices come in range to each other. A piconet is a collection of devices connected via Bluetooth technology in an ad hoc fashion. A Piconet can be a simple connection between two devices or more than two devices. Multiple independent and non-synchronized piconets can form a scatternet. Any of the devices in a piconet can also be a member of another by means of time multiplexing. i.e a device can be a part of more than one piconet by suitably sharing the time. The Bluetooth system supports both point-to-point and point-to-multi-point connections. When a device is connected to another device it is a point to point connection. If it is connected to more that one (upto 7 ) it is a point to multipoint connection. Several piconets can be established and linked together ad hoc, where each piconet is identified by a different frequency hopping sequence. All users participating on the same piconet are synchronized to this hopping sequence. If a device is connected to more than one piconet it communicates in each piconet using a different hopping sequence. A piconet starts with two connected devices, such as a portable PC and cellular phone, and may grow to eight connected devices. All Bluetooth devices are peer units and have identical implementations. However, when establishing a piconet, one unit will act as a master and the other(s) as slave(s) for the duration of the piconet connection. In a piconet there is a master unit whose clock and hopping sequence are used to synchronize all other devices in the piconet. All the other devices in a piconet that are not the master are slave units. A 3-bit MAC address is used to distinguish between units participating in the piconet. Devices synchronized to a piconet can enter power-saving modes called Sniff and hold mode, in which device activity is lowered. Also there can be parked units which are synchronized but do not have a MAC addresses. These parked units have a 8 bit address, therefore there can be a maximum of 256 parked devices.

Voice channels use either a 64 kbps log PCM or the Continuous Variable Slope Delta Modulation (CVSD) voice coding scheme, and never retransmit voice packets. The voice quality on the line interface should be better than or equal to the 64 kbps log PCM. The CVSD method was chosen for its robustness in handling dropped and damaged voice samples. Rising interference levels are experienced as increased background noise: even at bit error rates up 4%, the CVSD coded voice is quite audible.

What are the Applications?

(Major Portion of Content Provided by Puneet Gupta - a MobileInfo.Com Technology Writer)

Bluetooth has a tremendous potential in moving and synchronizing information in a localized setting. Potential for Bluetooth applications is huge, because we transact business and communicate more with people who are close by than with those who are far away - a natural phenomenon of human interaction. The following list represents only a small set of potential applications - in future many more imaginative applications will come along:

* By installing a Bluetooth network in your office you can do away with the complex and tedious task of networking between the computing devices, yet have the power of connected devices. No longer would you be bound to fixed locations where you can connect to the network. Each Bluetooth device could be connected to 200 other devices making the connection of every device with every other possible. Since it supports both point to point and point to multipoint it will virtually make the maximum number of simultaneously linked devices unlimited.

* The Bluetooth technology connects all your office peripherals wirelessly. Connect your PC or notebook to printers, scanners and faxes without the ugly and trouble some cable attachments. You can increase your freedom by connecting your mouse or the keyboard wirelessly to your computer.

* If your digital cameras in Bluetooth enabled, you can send still or video images from any location to any location without the hassle of connecting your camera to the mobile phone on the wireline phone.

* Bluetooth allows us to have three way phones. At home, your phone functions as a portable phone (fixed line charge). When you're on the move, it functions as a mobile phone (cellular charge). And when your phone comes within range of another mobile phone with built-in Bluetooth wireless technology it functions as a walkie-talkie (no telephony charge).

* In meetings and conferences you can transfer selected documents instantly with selected participants, and exchange electronic business cards automatically, without any wired connections.

* Connect your wireless headset to your mobile phone, mobile computer or any wired connection to keep your hands free for more important tasks when you're at the office or in your car.

* Have automatic synchronization of your desktop, mobile computer, notebook (PC-PDA and PC-HPC) and your mobile phone. For instance, as soon as you enter your office the address list and calendar in your notebook will automatically be updated to agree with the one in your desktop, or vice versa.

* Automatic Message Delivery: Compose e-mails on your portable PC while you're on an airplane. As soon as you've landed and switched on your mobile phone, all messages are immediately sent.

* Upon arriving at your home, the door automatically unlocks for you, the entry way lights come on, and the heat is adjusted to your pre-set preferences.

* IBM researchers are working on a number of personal devices like a WatchPad that could be connected with other devices through Bluetooth. The Watch Pad is very thin and contains 8MB of RAM. They are also working on a version of CyberPhone called CyberPhone - that can project data onto a small mirror. The CyberPhone can show as much information as a small PDA because of high resolution VGA screen.

You enter the airport-waiting lounge, equipped with Bluetooth-enabled Internet ports. Via the ports, you and other guests use Bluetooth-enabled laptops, PDAs, and other devices to access your office or home-based servers via the airline server. Using voice-over IP, you also make "free" Internet voice calls courtesy of your airline.