Bluetooth

Bluetooth The Bluetooth technology was developed to provide a wireless inter-connect between small mobile devices and their peripherals. Target markets were the mobile computer, the mobile phone, small personal digital assistants and peripherals. These markets were 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 Area Network (WLAN) technology, for which there were already many in the market and many more being developed. Rather, whereas WLANS are designed to efficiently connect large groups of people over a common backbone, the Bluetooth technology was designed to connect mobile devices over a personal and private connection. The Bluetooth technology tries to emulate the cost, security, and capabilities of common cables carried by mobile travelers. The technology must be as secure as a cable must be manufactured for about the same cost as must connect to a variety of devices available to the mobile user (seven simultaneous connections) and support data rates that are consistent with a mobile traveler's needs (1 Mega symbol per second data rates per piconet); must support many simultaneous and private connections (hundreds of private piconets within range of each other) ; must support the types of data used by mobile users (voice and data) ; and must be very low power and compact to support the small portable devices into which the technology will be integrated. Finally, the technology must be global as the mobile devices will travel and must 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 focused on 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 usage models and involves connecting a computing device to a Communicating device via a secure wireless link. 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. 2. Peripheral Interconnects: The second category of uses, peripheral interconnects, involves connecting other devices together. 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. 3. Personal Area Networking: The last usage model, Personal Area Networking (PAN), focuses on the ad-hoc formation and breakdown of personal networks. Imagine meeting someone in an airport and quickly and securely exchanging documents by establishing a private piconet. Bluetooth Architecture Figure: Bluetooth Architecture Bluetooth stack differ from the seven layer OSI model as it his feature to support Adhoc network among all participating nodes. Lowest layer in Bluetooth Architecture is the radio layer. Its interface specification defines 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 (media access 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 configuring baseband connections. And these control message definitions are part of the link manage protocol (LMP) the functional entity responsible for carrying out the processing associated with LMP is called link manager. On chip integration reduces the cost of the network interface and its small size make easy to put this chip in to several devices like cell phones etc. A Bluetooth chip can be connected to its host processor using USB, or PC-card interface. A specification called Host Controller Interface (HCI) specification defines a standard interface independent method of communicating with the Bluetooth chip. The software stack on the host processor communicates with the Bluetooth hardware using HCI commands. Since no hardware specific knowledge in needed so the Bluetooth stack software can easily be ported from one Bluetooth chip to another. HCI layer is the part of Bluetooth stack but it can't make peer to peer communication layer as it is unable to flow over the air link.