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  1. 1. Bluetooth By John Phillips The art of connecting things is becoming more and more complex every day. With the invention of Bluetooth technology, it is made to simplify the way people use electronics in accordance to other electronics. The new innovation has given a solution to give cable-free computer connections, which means real freedom to working environment regardless of location and wire availability. The technology allows portable computers, notebooks, mobile phones, personal digital assistant and other handy gadgets to make use of "short range, low power" radio technology to connect to each other. With this new invention, there is no doubt whether or not it will replace the inconsistency of infrared, which is used for most television remotes, connections in the sense that there does not need to be a line-of-sight connection to other devices. With Bluetooth it is possible to be in another room and still be able to access another device with no use of wires. The Bluetooth Special Interest Group, or SIG, is a group of companies working together to promote and define the Bluetooth specifications. The Bluetooth SIG was founded by five companies to develop the Bluetooth concept as a possible wireless technology standard, which are Ericsson, Intel, IBM, Toshiba and Nokia. Other companies like Microsoft, Lucent, 3Com and Motorola later joined the Bluetooth SIG. Today there are more than 1,500 companies have joined this group and the specifications are developed, published and promoted by the Bluetooth SIG. Bluetooth’s goals
  2. 2. expanded to include standardized wireless communications between any electrical devices and created a notion of Personal Area Network. The main competing technology against Bluetooth is infrared, which now is the standard that most people use for wireless connections. Infrared is a “line of sight” technology, meaning a direct connection is needed from the transmitter to the receiver. Knowing this, it is very uncommon for people to have something that would interfere with the direct connection to that receiver. Infrared communications are also a lot more cost efficient and cost a lot less to install into devices. One of the main downsides to infrared, however, is that it is a one-to-one technology, meaning that you can only send data from one device to another, such as a personal digital assistant to a computer, but not able to send data from a laptop to a computer.i This is where Bluetooth comes into play, because it allows numerous devices to communicate back and forth without needing a line-of-sight connection. The technology of Bluetooth centers around a 9mm x 9mm microchip, which functions as a low cost and short range radio link (see picture below).ii A Bluetooth device consists of a radio unit, a link control unit, and a support unit, where the link management takes place. The interface of a Bluetooth device consists of the Radio and Baseband layer, and the Link Manager Protocol (LMP). The Radio is responsible for transmitting data via radio waves over the air. The Baseband, which has both soft and hardware, controls the radio and is responsible for lower level encryption. The Link Manager Protocol is in charge of link setup, authentication, and link configuration. The radio transceiver operates on the 2.4 GHz IM band which is defined as 2,400-2,483 MHz. These radios use a spread spectrum, frequency hopping, and full-duplex signal at up to
  3. 3. 1600 hops/sec. The signal hops among 79 frequencies at 1 MHz intervals to give a high degree of interference immunity. Up to seven simultaneous connections can established and maintained as seen in picture below.iii For Bluetooth, information exchange happens ( - above left ( - above right through packets on a channel, where each packet as a different hop frequency, provided by the baseband to the radio. A combination of circuit switching and packet switching is used, where slots are reserved for synchronous packets. The minimum number of devices communicating is 2 units, which are referred to as a point-to-point connection. Any more than 2 units are called a point-to-multipoint connection. Using two or more of these units forms a personal-area network (PAN) or piconet with one master, which is the controlling channel – the other units, 7 at maximum, are called slaves. In the picture above, the PDA is serving as the master, and the other devices being the slaves. Two types of links between the master and slaves are possible: the synchronous connection- oriented link (SCO), being the point-to-point link, and the asynchronous connectionless link (ACL), being the point-to-multipoint link. The Link Manager Protocol is responsible for link setup, control, and security. If two devices fail to communicate with
  4. 4. each other, a common link key has to be initiated in order to transfer data. The process of establishing links in order to transfer data at a future time is called a pairing. For authentication, the verifier (either master or slave) sends a random number to the claimant, which in turn calculates a response, including the secret key. Both devices share the same secret key. If a slave is receiving and sending an authentication request at once, it first accepts the incoming request by an authentication response and then starts its own attempt. However, if a master is receiving and sending an authentication request at once, it declines the incoming request first, while the slave is accepting the master's request, and then the latter can restart another attempt. ( Authentication takes place directly, when two devices communicated before, i.e. if a link key has already been established.iv For encryption, a temporary link key must be issued from the master to the whole piconet, while every device as to agree on the use
  5. 5. of encryption, for example whether point-to-point or broadcasting packets should be encrypted. Then, the master is configured to only receive encrypted packages after what the slave is configured to transmit and receive encrypted packages. There is much strength to this new Bluetooth technology; however, there are also a few disadvantages. One of the main disadvantages is that Bluetooth operates on a relatively small bandwidth of about 721kb, and has a maximum range of roughly 30ft. There is also limited voice compatibility. The elimination of spaghetti cords is the main advantage that most technical and non-technical can relate to. The problem with this is that Infrared communication is already the standard, and even though it tends to be less reliable, the average user might tend to be skeptical about accepting a new standard. Bluetooth was originally created for the businessman on the go, therefore being a lot more convenient for them rather than the average computer user. Security is also a problem. Bluetooth's discovery protocol lets devices automatically find and start interacting with each other, unintentionally exposing access and data to unauthorized users. There is a huge chance that packets of data can be intercepted as information is being transferred between devices. Network managers must plan for users toting around instant access to their corporate networks wherever they travel. The narrow, point and shoot, type of application, such as crowded situations in which two people wish to exchange information while others are trying to do the same thing, is a strength of Infrared. “In such situations, a Bluetooth device, which is omni directional, would be at a disadvantage, as it might have trouble finding an individual device among many.”v Bluetooth was designed to avoid conflict with other devices using spread-spectrum frequency hopping. Bluetooth is compromised by a lack of standard feature performance.
  6. 6. “Because manufacturers have implemented certain Bluetooth capabilities differently, devices of different brands often can't communicate with each other. This leads to a number of problems, not the least of which is failure to negotiate spectrum use between devices from different manufacturers.”vi Another main advantage of Bluetooth is that devices can establish connections through walls, and once that connection is established, other devices do not have to be stationary. It is highly suitable for small devices such as cordless phones, headsets for cell phones, etc. There is a large market for Bluetooth technology. It will be compatible for all cell phone and computer users. People will be able to virtually eliminate wired with the use of this technology, for example using wireless keyboards, and mice in accordance to your computer. “The [Acura] TL uses the technology in its patented HandsFreeLink phone system that allows the Bluetooth-enabled cell phone to communicate wirelessly, securely -- and flawlessly with the car from a maximum distance of 30 feet.”vii Users will be able to access data using a PDA, for example, from a laptop across the room without needing a line-of-site connection. Many of the latest cellular phones are being equipped with this Bluetooth technology, and will soon become the standard of wireless connection between devices, and is the perfect innovation for the on the go consumer. i ii Monson, Heidi, “Bluetooth technology and implications” System Optimization Information, December 14th, 1999 (date visited, December 2, 2003) iii iv Bluetooth SIG, Specification of the Bluetooth system, Link Manager Protocol, Part C. Version 1.1, March 20th 2003, v vi Thurmond, Bob, “2001 Bluetooth Reigns?” Wall Street Technology Association, Ticker, June 6th , 2001 vii “All Around , A Sound System” The Washington Post, November 23rd , 2003