4.5 BLUETOOTH

• In 1994, the Swedish company L. M. Ericsson became interested in connecting its mobile phones to other devices (e.g., laptops) without cables. Together with four other companies (IBM, Intel, Nokia, and Toshiba), it formed a SIG (Special Interest Group, i.e., consortium) in 1998 to develop a wireless standard for connecting computing and communication devices and accessories using short-range, low-power, inexpensive wireless radios.
• The project was named Bluetooth, after Harald Blaatand (Bluetooth) II (940–981), a Viking king who unified (i.e., conquered) Denmark and Norway, also without cables.
• The Bluetooth protocols let these devices find and connect to each other, an act called pairing, and securely transfer data.
• The basic unit of a Bluetooth system is a piconet, which consists of a controller node and up to seven active worker nodes within a distance of 10 meters.
• . An interconnected collection of piconets is called a scatternet.
• At the time of this writing, there are more than two dozen applications, which are called profiles.
• The link protocol above the line is L2CAP (Logical Link Control Adaptation Protocol).
• This process reduces the harmful interference. It is called adaptive frequency hopping.
• The link manager protocol sets up logical channels, called links, to carry frames between the controller and a worker device that have discovered each othe
• The new secure simple pairing method enables users to confirm that both devices are displaying the same passkey, or to observe the passkey on one device and enter it into the second device. T
• The first is the SCO (Synchronous Connection Oriented) link. It is used for real-time data, such as telephone connections.
• The other kind is the ACL (Asynchronous ConnectionLess) link. This type of link is used for packet-switched data that is available irregularly.
• The Address field identifies which of the eight active devices the frame is intended for. The Type field identifies the frame type (ACL, SCO, poll, or null), the type of error correction used in the data field, and how many slots long the frame is. The Flow bit is asserted by a worker when its buffer is full and cannot receive any more data. This bit enables a primitive form of flow control.
• The Acknowledgement bit is used to piggyback an ACK onto a frame. The Sequence bit is used to number the frames to detect retransmissions. The protocol is stop-and-wait, so 1 bit is enough. Then comes the 8-bit header Checksum.
• In June 2016, the Bluetooth Special Interest Group introduced Bluetooth 5. In January 2019, it came out with Bluetooth 5.1