On the ground, our communication is covered by network signals of base stations 4G and 5G, and navigation can also be directly positioned by Beidou. In the underground, the signal waves received indoors are weakened or even blocked due to the occlusion of buildings, which leads to the phenomenon of weak underground communication signals. At the same time, the high-speed operation of the subway increases the difficulty of locating underground signals.
On March 20th, China's first subway Beidou positioning system started construction in Beijing. The project "Key Technologies for Efficient Traffic and Safety Services of Metro System in Megacities" adopts indoor Beidou +5G fusion positioning technology to broadcast indoor positioning signals, so that users can receive navigation positioning signals and improve the positioning accuracy of underground space of subway stations to more than 2m. The system can be used for vehicle dispatching, passenger transportation organization and emergency treatment. At the same time, passengers can use mobile phone maps in underground environment to realize positioning and navigation in subway stations through three-dimensional navigation.
What is the charm of Beidou +5G?
Beidou satellite navigation system (Beidou system for short) mainly provides all-weather and all-day positioning, navigation and timing services for users around the world. On July 3, 2020, the Beidou-3 system was completed and opened to provide global services, and the Beidou system entered a new stage of comprehensive promotion and application.
Beidou system mainly solves the outdoor positioning needs, and has been basically applied in transportation, agriculture, forestry and fishery, hydrological monitoring, weather forecasting, disaster relief and public safety. Its outdoor positioning accuracy is about 10 meter, speed measurement accuracy is 0.2 meter per second, and timing accuracy is about 20 nanoseconds. However, due to the fact that satellite signals can't cover indoors, their immunity to the environment is poor, and they can't meet the necessary conditions of indoor positioning and outdoor shielding, so their indoor application is greatly limited.
5G networking is deployed by base stations, which has the advantages of dense networking, large bandwidth and multiple antennas. The air interface delay is as low as 1ms, and the mobility supports high-speed movement of 500 km/h. The positioning technology based on 5G communication network can achieve sub-meter or even decimeter positioning accuracy indoors.
In the underground environment with high-speed traffic like subway, the deep integration of Beidou +5G can build an indoor and outdoor coverage positioning system. Combining the advantages of large bandwidth, low delay and wide connection of 5G with the navigation and positioning ability of Beidou system, the positioning accuracy of complex indoor environment is greatly improved.
Subway Beidou positioning system is the first application of Beidou +5G scheme in subway, but in fact, this fusion positioning technology has already appeared in the market. In April, 20021,China Mobile developed a 5G+ Beidou precise navigation system, which was tested in Chongqing Jiefang North Underground Ring Road.
Indoor positioning is just needed.
RFID (radio frequency identification) technology: using radio frequency, the fixed antenna forms an electromagnetic field, and the tag attached to the object generates and transmits data through the magnetic field induced current, and exchanges data in a non-contact two-way communication mode to realize the purpose of mobile device identification and positioning. The positioning information of centimeter level can be obtained within several milliseconds, and the electromagnetic field has the advantage of non-line-of-sight (NLOS). RFID indoor positioning technology also has the characteristics of large transmission range and low cost. However, it has no communication ability, poor anti-interference ability, is not easy to integrate into other systems, and is not perfect for users' safety and privacy protection and international standardization, so it is generally used for logistics and warehouse positioning.
WiFi technology: There are two indoor locations of WiFi. One is to use the wireless local area network composed of mobile devices and wireless network access points to locate and track people and vehicles more accurately through differential algorithm. The other is to record the signal strength of a large number of determined location points in advance, and complete the positioning and tracking by comparing the signal strength of new equipment with a huge database. The highest accuracy of WiFi location is about 1 m to 20 m, but Wi-Fi access points usually only cover the area with a radius of about 90 m, which is easily interfered by other signals, and the energy consumption of the locator is also relatively high.
ZigBee technology: ZigBee is a short-distance, low-rate wireless network technology. It mainly uses radio waves to transmit data from one sensor to another, and locates the position of equipment through coordinated communication between sensors. Therefore, the most prominent feature of ZigBee is low power consumption and low cost, but its limitation is that signal transmission is greatly influenced by multipath effect and motion, and its diffraction ability is weak, and its ability to penetrate walls is weak. Personnel on-the-job management system is widely used in large factories and workshops.
Bluetooth technology: As a short-distance, low-power wireless transmission technology, Bluetooth access point is used to connect users, and the location information of users can be obtained by detecting the signal strength. The biggest advantage of Bluetooth is its small size, short distance, low power consumption and easy integration in mobile devices such as mobile phones. However, for the complex space environment, the stability of Bluetooth positioning system is slightly poor, and it is greatly interfered by noise signals. In recent years, Bluetooth AOA, based on receivers and transmitters, can measure beacon signals through multiple antennas in the confirmation area, and calculate the precise orientation of beacon equipment by triangulation method, with the accuracy as high as 0. 1. However, the deployment environment of Bluetooth AOA is mostly required to be within the precision scene of 1-3 meters.
Ultra-wideband (UWB) technology: UWB is a wireless communication technology with high transmission rate, low transmission power and strong penetration ability, based on ultra-narrow pulses. It does not need to use the carrier wave in the traditional communication system, but transmits data by sending and receiving ultra-narrow pulses of nanosecond or microsecond level, so it has a bandwidth of 3. 1~ 10.6GHz, and the positioning accuracy of UWB can reach sub-meter level, which is mostly used for indoor static or moving living body positioning and tracking, but there are still problems in power consumption and cost optimization.
Fusion positioning is the future trend.
Six common indoor positioning technologies are mentioned above, but the fragmentation of the Internet of Things makes a single technology unable to meet the application requirements of the scene, so integrated positioning has become the trend of industry demand.
The White Paper on the Development of Satellite Navigation and Location Service Industry in China released by China Satellite Navigation and Positioning Association last year pointed out that in 2020, the total output value of the whole industry will increase by 16.9% year-on-year, reaching 403.3 billion yuan. Among them, the growth rate of high-precision positioning market far exceeds that of the whole industry, with a year-on-year growth of 47.5% in 2020, with a total output value of1/kloc-0.04 billion yuan. From 20 10 to 2020 1 1, the annual sales revenue of high-precision positioning products increased by 10 times, with a compound annual growth rate of 26%.
Single positioning technology can't fill the demand of mass market differentiation, so integrated positioning technologies like Beidou+,5G+ and UWB+ are gradually introduced, and the industrial chain is gradually improved. Like autonomous driving and intelligent transportation, "Beidou +5G" technology has become a new solution in the stage of rapid technological evolution; In the personnel positioning system of smart mine, "UWB+ZigBee" technology is more flexible than using UWB alone. Fusion positioning can make up for the defects of single positioning technology, optimize the power consumption, cost and positioning accuracy in scene application, and create a refined positioning scheme.
In the future, integrated positioning will shine brilliantly.