Bluetooth The Bluetooth technology was developed to provide a wireless inter-connect betweensmall mobile devices and their peripherals. Target markets were the mobile computer,the mobile phone, small personal digital assistants and peripherals. These marketswere represented by the companies who created the technology: Intel, 3COM,Ericsson, IBM, Motorola, Nokia, and Toshiba, and were further supported by the 1,600 other early adopter companies. The goals of the technology did not include developing another Wireless Local AreaNetwork (WLAN) technology, for which there were already many in the market andmany more being developed. Rather, whereas WLANS are designed to efficientlyconnect large groups of people over a common backbone, the Bluetooth technologywas designed to connect mobile devices over a personal and private connection. The Bluetooth technology tries to emulate the cost, security, and capabilities ofcommon cables carried by mobile travelers. The technology must be as secure as acable must be manufactured for about the same cost as must connect to a variety ofdevices available to the mobile user (seven simultaneous connections) and supportdata rates that are consistent with a mobile traveler's needs (1 Mega symbol persecond data rates per piconet); must support many simultaneous and privateconnections (hundreds of private piconets within range of each other) ; must supportthe types of data used by mobile users (voice and data) ; and must be very low powerand compact to support the small portable devices into which the technology will beintegrated. Finally, the technology must be global as the mobile devices will travel andmust work with devices found in other parts of the world. Usage Model While the Bluetooth usage model is based on connecting devices together, it is focusedon three broad categories: voice/data access points, peripheral interconnects, Personal Area Networking (PAN). 1. Voice/Data Access Points: Voice/data access points is one of the key initial usagemodels and involves connecting a computing device to a Communicating device via asecure wireless link. For example, a mobile computer equipped with Bluetoothtechnology could link to a mobile phone that uses Bluetooth technology to connect tothe Internet to access e-mail. The mobile phone acts as a personal access point. Evenmore ideal, the notebook can connect to the Internet while the cell phone is beingcarried in a briefcase or purse. The Bluetooth usage model also envisions public dataaccess points in the future. Imagine the current data-equipped pay phones in airportsbeing upgraded with Bluetooth modems. This would allow any mobile device equippedwith Bluetooth technology to easily connect to the Internet while located within tenmeters of that access point.
2. Peripheral Interconnects: The second category of uses, peripheral interconnects,involves connecting other devices together. Imagine standard keyboards, mice, andjoysticks that work over a wireless link The Bluetooth link is built into the mobilecomputer; therefore, the cost of the peripheral device is less because an access point isnot needed. Additionally, many of these devices can be used in multiple markets. Forexample, a Bluetooth headset used in the office could be connected to a Bluetoothaccess point that provides access to the office phone and multi-media functions of themobile computer. 3. Personal Area Networking: The last usage model, Personal Area Networking (PAN),focuses on the ad-hoc formation and breakdown of personal networks. Imaginemeeting someone in an airport and quickly and securely exchanging documents byestablishing a private piconet. Bluetooth Architecture Figure: Bluetooth Architecture Bluetooth stack differ from the seven layer OSI model as it his feature to support Ad-hoc network among all participating nodes. Lowest layer in Bluetooth Architecture is the radio layer. Its interface specificationdefines the characteristics of the radio front end frequency bands channel arrangements Permissible transmit power levels
Receiver sensitivity level Next layer is the baseband which carried out Bluetooth's Physical and MAC (mediaaccess control) processing, this perform following task Device discovery Link formation Synchronous and Asynchronous communication with peers. Bluetooth peer exchange many control messages for managing and configuringbaseband connections. And these control message definitions are part of the link manage protocol (LMP) thefunctional entity responsible for carrying out the processing associated with LMP iscalled link manager. On chip integration reduces the cost of the network interface and its small size makeeasy to put this chip in to several devices like cell phones etc. A Bluetooth chip can beconnected to its host processor using USB, or PC-card interface. A specification called Host Controller Interface (HCI) specification defines a standardinterface independent method of communicating with the Bluetooth chip. The software stack on the host processor communicates with the Bluetooth hardwareusing HCI commands. Since no hardware specific knowledge in needed so theBluetooth stack software can easily be ported from one Bluetooth chip to another. HCIlayer is the part of Bluetooth stack but it can't make peer to peer communication layeras it is unable to flow over the air link.