Application of Bluetooth Technology in Automatic Fire Alarm System

      Modern communication technology is moving towards packetization of network core technology and wirelessization of narrowband access technology. In the field of wireless access, circuit-based transmission and packet transmission technology were used in the early days. Recently, the Bluetooth Special Interest Group SIG, which consists of five companies including Ericsson, Intel, Nokia, Toshiba and IBM, jointly launched the Bluetooth project. Bluetooth is gradually becoming a new star in the field of data transmission with its small size, low cost and strong penetration. The use of Bluetooth technology to achieve wireless transmission in the automatic fire alarm system has advantages that other technologies cannot match.

　　1. Introduction to Bluetooth Technology

　　"Bluetooth" technology is an open standard for universal wireless signal transmission interface and its control software, and is a technical specification with a low form factor for short-range wireless connection devices. Its purpose is to make the network ubiquitous, that is, to replace the existing network connection with wireless technology, so that hardware produced by different manufacturers can have the possibility of exchanging information and cross-operation within a short range under the condition of wireless connection. It is based on low-cost short-range wireless connection, provides a universal interface for existing digital networks and peripherals, thereby forming a special connection device group of a long-distance fixed network, and uses radio waves to transmit data or other digital content between two electronic devices.

　　The Bluetooth system consists of four functional units: wireless unit, link control unit, link management, and software functions. Its core technology is a microchip set consisting of a baseband and a radio frequency chip, both of which are 9mm×9mm in size. The baseband chip performs simple digital information processing through the built-in wireless communication protocol, allowing different Bluetooth products to exchange data; the radio frequency chip is responsible for transmitting signals. Bluetooth technology emphasizes small size, low power, and low unit price, and supports point-to-point and point-to-multipoint connections. We usually call all devices connected together through Bluetooth technology a piconet. Several piconets can be connected together, and each piconet is identified by the frequency hopping sequence. All users of the same piconet are synchronized with this frequency hopping sequence. Its topology can be described as a "multi-piconet" structure, in which the full-duplex data rate can exceed 6Mb/s with 10 fully loaded independent piconets.

　　Modern communication technology is moving towards packetization of network core technology and wirelessization of narrowband access technology. In the field of wireless access, circuit-based transmission and packet transmission technology were used in the early days. Recently, the Bluetooth Special Interest Group SIG, which consists of five companies including Ericsson, Intel, Nokia, Toshiba and IBM, jointly launched the Bluetooth project. Bluetooth is gradually becoming a new star in the field of data transmission with its small size, low cost and strong penetration. The use of Bluetooth technology to achieve wireless transmission in the automatic fire alarm system has advantages that other technologies cannot match.

　　Other features of Bluetooth:

　　1. Bluetooth works in the internationally open 2.4GHz ISM (industrial, scientific, and medical) frequency band. In this frequency band, users do not need to apply for frequency use rights from a special management agency to use the device;

　　2. Frequency hopping spread spectrum technology is used to divide 79 frequency points between 2.4GHz and 2.4835GHz. The frequency hopping determined by the main unit of the piconet is a random sequence of 1600 hops per second, making the wireless link itself more secure and anti-interference;

　　3. Transmission distance. The current working distance is within 10 meters, and it can reach 100 meters after increasing the RF power. Such a working range allows Bluetooth to ensure a higher data transmission rate, while reducing interference from other electronic products and radio technologies, which is beneficial to the security of the system;

　　4. The modulation method adopts GFSK, BT=0.5, positive frequency deviation represents 1, and negative frequency deviation represents 0;

　　5. Using time division multiplexing multiple access technology, each Bluetooth device sends data in its own time slot in the form of data packets, which can effectively avoid problems such as "collision" and "hidden terminal" in wireless communication;

　　6. Supports two connection types: synchronous connection-oriented (SCO) and asynchronous connectionless (ACL). Both connection types use TDD (time division duplex transmission scheme) to achieve full-duplex transmission;

　　7. The baseband controller uses three error correction schemes to achieve error-free data transmission;

　　8. The air interface is based on an antenna level of 0dBm and complies with the FCC (Federal Communications Commission) standard for the ISM band with a level of 0dBm;

　　9. Comply with the Bluetooth 1.0b version specification: the software version is re.1.08, and the hardware version is DIG8043390.