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Introduction to Bluetooth Technology
Bluetooth is a radio frequency specification for short range, point to point and point to multi point voice and data transfer. Bluetooth technology facilitates the replacement of cables normally used to connect one device to another by a short range radio link. With the help of blue tooth we can operate our keyboard and mouse without direct connection of CPU. Printers, fax machines, headphone, mouse, keyboard or any other digital devices can be part of Bluetooth system.
In spite of facilitating the replacement of cables, Bluetooth technology works as an universal medium to bridge the existing data networks, a peripheral interface for existing devices and provide a mechanism to form short ad hok network of connected devices away from fixed network infrastructures.
Due to their independence on short range radio link, Bluetooth devices do not require a line of site connection in order to communicate. Therefore a computer can print information on a printer if printer is in inside the room. Two blue tooth devices can talk to each other when they come within range of 10 meters to each other.
Bluetooth technology represents an opportunity for the industry to deliver wireless solutions that are ubiquitous across a broad range of devices.
Why it’s name is Bluetooth?
While many new technologies bear technical names, like RS-232 or IEEE
802.11b, Bluetooth, the wireless technology, is different.
Bluetooth was named for the 10th Century Viking king , Harald Blatand
(A.K.A., Bluetooth) who peacefully united all the tiny island kingdoms of
Denmark, southern Sweden, and southern Norway into one country . In
keeping with its namesake, Bluetooth, the new low-cost radio technology, is
designed to unite or connect all different types of devices to effectively work
as one. By uniting devices, Bluetooth eliminates the need for cabling in a
wide range of products, including cellular phones, PCs, headphones, audio
equipment, printers, and many more.
• Piconet: Devices connected in an ad hoc fashion, that is, not requiring predefinition and planning, as with a standard network. Two to eight devices can be networked into a piconet. It is a peer network, that is, once connected, each device has equal access to the others. However, one device is defined as master, and the others as slaves.
• Scatternet: Several piconets may form a larger scatternet, with each piconet maintaining independence.
• Master unit: The master in a piconet whose clock and hopping sequence synchronizes the other devices.
• Slave unit: Devices in a piconet that are not the master.
• MAC address: Three bit address that distinguishes each unit in a piconet.
• Parked units: Piconet devices that are synchronized but don't have MAC addresses.
• Sniff and hold mode: Power-saving mode of a piconet device.
How Bluetooth Technology Work
The technology of Bluetooth centers around a 9mm x 9mm microchip, which functions as a low cost and short range radio link. Bluetooth Technology provide a 10 meter personal bubble that support simultaneous transmission of both voice
and data for multiple devices. Up to 8 devices can be connected in a piconet, and uo to 10 piconets can exist within the 10 meter bubble. Each piconet support
up to 3 simultaneous full duplex voice devices.
The gross data rate is 1 Mb/s, but the actual data rate are 432 kbps for full
duplex transmission,721/56kbps for asymmetric transmission, and 384 kbps for
Bluetooth wireless technology is designed to be as secure as a wire with up to 128-bit public/private key authentication, and streaming cipher up to 64 bit based on a5 security.
Transmission types and rates :
The baseband (single channel per line) protocol combines circuit and packet switching. To assure that packets do not arrive out of order, slots (up to five) can be reserved for synchronous packets. As noted earlier, a different hop signal is used for each packet. Circuit switching can be either asynchronous or synchronous. Up to three synchronous (voice) data channels, or one synchronous and one asynchronous data channel, can be supported on one channel. Each synchronous channel can support a 64 Kb/s transfer rate, which is fully adequate for voice transmissions. An asynchronous channel can transmit as much as 721 Kb/s in one direction and 57.6 Kb/s in the opposite direction. It is also possible for an asynchronous connection to support 432.6 Kb/s in both directions if the link is symmetric.
Radio frequency and spectrum hopping :
What if there's a lot of radio noise? Won't that interfere with Bluetooth connections? As a rule, the answer is no. It is designed to use fast acknowledgement and frequency hopping, which will make connections robust. It is packet-based, and will jump to a new frequency after each packet is received, which not only helps limit interference problems, but also adds to security. Data rates are one megabyte/second, including headers. Full duplex transmissions (both directions at once) are accomplished via time division multiplexing.
The Bluetooth radio chip functions at 2.4 gigahertz, which is in the unlicensed ISM (Industrial Scientific Medical) band. It separates the 2.4 gigahertz frequency band into 79 hops one megahertz apart, starting with 2.402 and ending with 2.480 (though this bandwidth is narrower in Japan, France, and Spain). This spread spectrum is used to hop from one channel to another, pseudo-randomly, which adds a strong layer of security. Up to 1600 hops per second can be made. The standard frequency range is 10 centimeters to 10 meters, and can be extended to at least 100 meters by increasing transmission power.
Data can be transmitted both synchronously and asynchronously. The Synchronous Connection Oriented (SCO) method is used primarily for voice, and Asynchronous Connectionless (ACL) is primarily for data. Within a piconet, each master-slave pair can use a different transmission mode, and modes can be changed at any time. Time Division Duplex (TDD) is used by both SCO and ACL, and both support 16 types of packets, four of which are control packets that are the same in each type. Because of the need for smoothness in data transmission, SCO packets are generally delivered via reserved intervals, that is, the packets are sent in groups without allowing other transmissions to interrupt. SCO packets can be transmitted without polling by the sending unit. ACL links support both symmetric and assymetric transmissions.
Bandwidth is controlled by the master unit, which determines how much of the total each slave unit can use. Slaves cannot transmit data until they have been polled by the master, and the master can broadcast messages to the slave units via ACL link.
Bluetooth network arrangements (topology) can be either point-to-point or point-to-multipoint. Any unit in a piconet can establish a connection to another piconet to form a scatternet. See the figure, which diagrams a scatternet in which piconet A, which consists of four units, is connected to piconet B, consisting of two units. Note that the master unit of A is not the link Bluetooth network arrangements (topology) can between the two piconets.
Error correction and security:
on code (FEC), 2/3 rate forward error correction code FEC, and automatic repeat request (ARQ). The FEC methods are designed to reduce the number of retransmissions. However, the over hea Three error correction techniques have been defined: 1/3 rate forward error corrected significantly slows transmissions, so is generally not used in relatively error-free environments, with the exception of packet headers. The ARQ scheme requires that the header error and cyclic redundancy checks are okay. When they are, an acknowledge is sent. When they aren't, the data is resent.
Security is provided in three ways: through pseudo-random frequency band hops, authentication, and encryption. Frequency band hops make it difficult for anyone to eavesdrop. Authentication allows a user to control connectivity to only devices specified. Encryption uses secret key lengths of 1, 40, and 64 bits. The quality of security is excellent for most applications. However, it is not the highest level available, and for those users who require it, the suggestion is to investigate separate network transfer protocols and security software.
Bluetooth connections are established via the following techniques:
1. Standby: Devices not connected in a piconet are in standby mode. In this mode, they listen for messages every 1.28 seconds over 32 hop frequencies (fewer in Japan, Spain, and France).
2. Page/Inquiry: If a device wishes to make a connection with another device, it sends out a page message, if the address is known, or an inquiry followed by a page message, if it is unknown. The master unit sends out 16 identical page messages on 16 hop frequencies to the slave unit. If there is no response, the master retransmits on the other 16 hop frequencies. The inquiry method requires an extra response from the slave unit, since the MAC address is unknown to the master unit.
3. Active: Data transmission occurs.
4. Hold: When either the master or slave wishes, a hold mode can be established, during which no data is transmitted. The purpose of this is to conserve power. Otherwise, there is a constant data exchange. A typical reason for going into hold mode is the connection of several piconets.
5. Sniff: The sniff mode, applicable only to slave units, is for power conservation, though not at as reduced a level as hold. During this mode, the slave does not take an active role in the piconet, but listens at a reduced level. This is usually a programmable setting.
6. Park: Park mode is a more reduced level of activity than the hold mode. During it, the slave is synchronized to the piconet, thus not requiring full reactivation, but is not part of the traffic. In this state, they do not have MAC addresses, but only listen enough to keep their synchronization with the master and check for broadcast messages.
Voice/Data Access Points:
Voice/data access points is one of the key initial usage models and involves connecting a computing device to a communicating device via a secure wireless link (see Figure 1). For example, a mobile computer equipped with Bluetooth technology could link to a mobile phone that uses Bluetooth technology to connect to the Internet to access e-mail. The mobile phone acts as a personal
access point. Even more ideal, the notebook can connect to the Internet while the cell phone is being carried in a briefcase or purse. The Bluetooth usage model also envisions public data access points in the future. Imagine the current data-equipped pay phones in airports being
upgraded with Bluetooth modems. This would allow any mobile device equipped with Bluetooth technology to easily connect to the Internet while located within ten meters of that access point. These access points could, of course, support much higher data rates than today’s modems, as public spaces could connect a variety of private Bluetooth access points via a LAN that is routed to the Internet over a DSL line, allowing each access point a private 1Mbps connection to the Internet.
Peripheral Interconnects :
The second category of uses, peripheral interconnects, involves connecting other devices together as shown in Figure 2. Imagine standard keyboards, mice, and joysticks that work over a wireless link. The Bluetooth link is built into the mobile computer; therefore, the cost of the peripheral device is less because an access point is not needed. Additionally, many of these devices can be used in multiple markets. For example, a Bluetooth headset used in the office could be connected to a Bluetooth access point that provides access to the office phone and multi- media functions of the mobile computer. When mobile, the same headset could be used to interface with the cellular phone (which can now remain in a
briefcase or purse).Another aspect of a short-range link like Bluetooth is in the area of proximity security devices. In this case, if one device is not within range of another device, the first device will go into a high security mode.
Bluetooth Special Interest group (SIG)
Bluetooth special group is group of companies working together to define, developed promote an open royalty free specification for seamless wireless connectivity and cable replacement for a wide variety of mobility-enhancing devices. The original charter of the SIG is to monitor the technical development of a short range radio and to create an open global standard. It prevent the technology from becoming the property of any single company.
In developing the Bluetooth specification, the SIG is strictly adhering to some basic principles that that can be summed up in five key words: freedom, security, simplicity, versatility and reliability. These keywords are the foundation of Bluetooth technology. To be Bluetooth certified, a device must pass interoperability testing by the Bluetooth Special Interest Group thus assuring that products meeting the specification will be able to interact with all other Bluetooth-certified products and with the Internet.
In february1998, the Special Interest Group (SIG) was formed. The founding SIG member are Ericsson, Intel, IBM, Nokia & Toshiba. Since then over 2000 adopter have joined including Compaq, Lucent, Motorola and 3com.
These are the features of the Bluetooth technology:
• It separates the frequency band into hops. This spread spectrum is used to hop from one channel to another, which adds a strong layer of security.
• Up to eight devices can be networked in a piconet.
• Signals can be transmitted through walls and briefcases, thus eliminating the need for line-of-sight.
• Devices do not need to be pointed at each other, as signals are omni-directional.
• Both synchronous and asynchronous applications are supported, making it easy to implement on a variety of devices and for a variety of services, such as voice and Internet.
• Governments worldwide regulate it, so it is possible to utilize the same standard wherever one travels.
While there is no single competing technology that covers the entire concept of Bluetooth wireless technology, in certain market segment other technology do exist.
For cable replacement, the infrared standard IrDA has been around for several years and is quite widespread. Most new portable PCs, PDAs, and some cellular phones support IrDA, although actual adoption by users has been rather limited. IrDA is faster than Bluetooth but is limited to point to point connections,
Whereas Bluetooth is also capable to point to multi point. IrDA’s biggest draw back is that it requires a clear line to sight, and is usually limited to a few feet between devices.
Wireless LAN based on the IEEE 802.11b standard are used to replace a wired LAN throughout a building. The transmission capacity is high and so is the number of simultaneous users. However, compared to Bluetooth, these wireless LANs are more expensive, consume more power and have a larger hardware footprint, making them unsuitable for small mobile devices.
Bluetooth in the Future
What is the future direction of the Bluetooth standard?
At this time, we anticipate the Bluetooth SIG to evolve the Bluetooth technology to provide greater bandwidth & distances, thus increasing the potential platforms & applications used in the emerging personal area-networking marketplace.
What is the future of Bluetooth?
Bluetooth is a continually expanding technology. There are plans to add many new application profiles. With over 1800 companies working on Bluetooth, the future could not be brighter. With a strong special interest group behind Bluetooth, the standardization of the application profiles is almost assured.
According to market researchers, Cahners In-Stat Group, it is anticipated that as many as 670 million products will have Bluetooth built-in by the year 2005.
Will the speed of Bluetooth increase?
Some members of the Bluetooth SIG such as Sony & Eastman Kodak are interested in seeing the speed of Bluetooth increasing for applications such as streaming video. Proposals are under consideration but it is not clear when products based on any of the proposals would be available
ADVANTAGES OF BLUETOOTH TECHNOLOGY:
1.No line of site restrictions as with IrDA.
2. Low power consumption makes integrated in battery powered devices
3. 2.4 GHz radio frequency ensures worldwide operability.
4. Tremendous momentum not only within the computer industry
but other industries like cellular telephones and transportation.
Homes equipped with Bluetooth devices may be able to recognise the arrival of its bonafide residents and unlock the door on their arrival. The device will also adjust heat to a preset temperature. While this is happening, the data from the individual’s PDA may be exchanged with the home electronic board, and the family calendar is updated
to reflect the scheduled activities in the office.
The Internet Bridge
An extension of this model could be a mobile computer that allows surfing the Internet irrespective of the location of the user, and regardless of whether the user is cordlessly connected through a mobile phone (cellular) or through a wire line connection (e.g. PSTN, ISDN, LAN, xDSL).
Hotels are testing, or plan to test, services that allow guests to check in, unlock room doors and even control room temperature with handheld devices equipped with Bluetooth Technology.
The Bluetooth enabled mobile phone or the PDA can present the electronic ticket to the airline system without one having to go through the queue at the check-in counters. The airline's on-line system performs the identification via the ID-tag feature built into the mobile phone or the PDA and confirms the reserved seat.
The Three-in-one Phone
With Bluetooth support, one handset will be able to provide multiple functionality. When at home, the phone functions as a cordless phone, connected to the fixed line. When on the move, it functions as a mobile phone connected to the mobile network. Additionally, when the phone comes within range of another mobile phone with built-in Bluetooth technology, it functions as a walkie-talkie.