introduction The Internet of Things is also known as the sensor network internationally. To a certain extent, it is another wave of information industry after computers, the Internet and mobile communications. In recent years, the consumption of automobiles has become a rapid growth trend. Due to the lagging road development and the low management level, the phenomenon of urban congestion is very serious. Under the concept of the Internet of Things, the application of automotive IoT technology will contribute to the intelligent level of urban traffic management. Improve and effectively improve urban traffic conditions. The Bluetooth technology includes sensor technology, identification technology, mobile communication technology, etc. These technologies are closely related to the Internet of Things. Because of this, Bluetooth has a very broad prospect for the Internet of Things in smart transportation. 1 Bluetooth technical characteristics In May 1998, five well-known manufacturers of Sweden ’s Ericsson, Finland ’s Nokia, Japan ’s Toshiba, the United States IBM and Intel Corporation proposed the concept of Bluetooth technology when jointly expanding the standardization activities of short-range wireless communication technology. Bluetooth works on the 2.4 GHz industrial frequency band (SIM) without a license (the frequency band of our country is 2 400.O ～ 2 483.5 MHz). The bandwidth of each channel of Bluetooth is 1 MHz, and the center frequency of adjacent channels is 1 MHz. To avoid out-of-band radiation and other interference, the upper and lower guard bands are specified as 3.5MHz and 2 MHz, respectively. Bluetooth adopts frequency hopping spread spectrum technology. A total of 79 frequency hopping points are set in the working frequency band. Within a 30 s period, the use time of any frequency point does not exceed 0.4 s, and the frequency hopping process is pseudo-random. According to the size of Bluetooth radio frequency power, it can be divided into 3 power levels, namely 100 mW for level 1, 2.5 mW for level 2, and 1 mW for level 3. These features of Bluetooth technology can better bear the end of the Internet of Things smart sensing and piconet mobile communication functions, especially suitable for the concept and technical requirements of the automobile Internet of Things. Each computer network card has a media access control address, or MAC address, which can distinguish the source and destination of the data on the network. Similarly, every Bluetooth transceiver in the world is uniquely assigned a 48-bit Bluetooth device address that complies with the IEEE 802 standard. The address space of the Bluetooth device address is 232 (about 4.29 billion). Each Bluetooth device manufacturer has the right to number the products it produces, which can be regarded as the only Bluetooth device address in the world, which provides technical solutions for wireless identification of car Internet of Things users, such as car positioning, car identity authentication , Car information query, car payment without parking, car remote control door and ignition, car anti-theft, etc. 2 Bluetooth application in smart cars 2.1 Bluetooth-based automotive Internet of Things The emergence of Bluetooth technology has attracted many attentions for more than a decade. In recent years, the application prospect of Bluetooth technology in the field of Internet of Things intelligent transportation is very promising. Vehicle electronic systems are developing in the direction of intelligence, informatization and networking. The automotive market has become an important growth point of China's economy. Wireless communication technology has broad application prospects in mobile systems such as automobiles. At first, Bluetooth technology was mainly used in the telephone communication of automobiles. However, with the continuous deepening of research and application, there will be more Bluetooth applications in automotive intelligence: such as remote vehicle condition diagnosis, vehicle safety system, vehicle-to-vehicle communication, multimedia download, etc. These are already the initial concepts of IoT smart cars. The Internet of Vehicles is an area that is highly valued by various countries and China. The European Union invested 300 million euros in October 2010 to study smart cars. Smart cars use many sensor technologies, and some cars will use more than 200 sensors. More and more, every part of these sensor cars needs to be connected to the network, so when the car is running, it can use the background alarm to show where the fault will occur, and at the same time it can reduce the rear-end of the car, solve the waiting time and exhaust Issues such as emissions are intelligent transportation and an essential part of "smart" cities. Bluetooth can fully assume the role of a sensor. Its miniaturization, high integration, sleep function, low cost, and openness are the basic characteristics of sensor wireless transmission. To sum up, the current expanded application scenarios of Bluetooth technology in automobiles are concentrated in the following aspects. 2.2 Application scenarios Hands-free phone When the user enters the car, the vehicle-mounted system will automatically connect to the user's mobile phone. During driving, users can use voice control to complete functions such as dialing, answering, hanging up, and volume adjustment without manual operation. They can make full-duplex hands-free calls through the microphone and sound system in the car. The Bluetooth device completely constitutes a piconet in the car to realize information exchange. Car remote control users can use the mobile phone with Bluetooth to control various switches in the door and car within 10 m, including the ignition control of the car. This application actually uses the characteristics of Bluetooth authentication "binding" and Bluetooth address "unique" to enhance the reliability and security of wireless remote control. Music download users can download music to the car stereo via mobile phone plus Bluetooth. The advantage lies in the intelligent and high-speed transmission of wireless links. Electronic navigation users can download electronic maps and other data to the car GPS navigation system through the mobile phone and Bluetooth. The navigation system obtains the current coordinate parameters from Bluetooth and transmits it back to the navigation center through the mobile phone text message to realize real-time vehicle positioning and navigation. Automobile fault diagnosis system The vehicle-mounted system can send the fault code and other information to the repair center through the mobile phone and Bluetooth. When the repair center sends someone to repair, it can prepare the corresponding accessories and repair tools according to the fault code and other information to eliminate the fault on site. The unique feature of vehicle location Bluetooth address provides a technical solution for vehicle identity confirmation and location. First of all, the Bluetooth on the car can be used as a reference through fixed objects with Bluetooth devices around the road, such as roadside signs, street lights, bridges, buildings, etc., and then the electronic map confirms its exact position. Secondly, a network composed of Bluetooth piconet and mobile communication can search for car location information in real time when needed. Car congestion At present, car congestion is a very prominent problem in large cities, especially in China, which has reached the point of non-governance. In addition to the rapid growth of vehicles, there is no intelligent information platform is also an important Aspect. The Bluetooth chip is cheap and has an address function, so the use of Bluetooth to form a piconet in the city can quickly establish a network, thereby realizing the requirements of traffic management informatization with minimal expenditure. On the one hand, the traffic control department can grasp the flow information and publish it in time (instead of live video) through the car with Bluetooth, and the car Bluetooth real-time system can prompt the driver to avoid the congested road and bypass.
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