Whether it is GPS positioning technology or the use of wireless sensor networks or other positioning means for positioning has its limitations. The trend of future indoor positioning technology is the combination of satellite navigation technology and wireless positioning technology. Combining GPS positioning technology with wireless positioning technology and exerting their respective advantages, it can provide better accuracy and response speed, and can also cover more Extensive range for seamless, accurate positioning... With the rapid increase of data services and multimedia services, people's demand for positioning and navigation is increasing, especially in complex indoor environments such as airport halls, exhibition halls, warehouses, supermarkets, libraries, underground parking lots, and mines. It is often necessary to determine the location information of the mobile terminal or its holders, facilities and articles indoors. However, due to the constraints of positioning time, positioning accuracy, and complex indoor environments, relatively well-established positioning technologies are still not well utilized. Therefore, experts and scholars have proposed many indoor positioning technology solutions, such as A-GPS positioning technology, ultrasonic positioning technology, Bluetooth technology, infrared technology, radio frequency identification technology, ultra-wideband technology, wireless local area network, optical tracking and positioning technology, and image analysis. , beacon positioning, computer vision positioning technology and so on. These indoor positioning technologies can be summarized in several categories as a whole, namely, GNSS technologies (such as pseudolites, etc.), wireless positioning technologies (wireless communication signals, radio frequency wireless tags, ultrasonic waves, optical tracking, wireless sensor positioning technologies, etc.), and other positioning technologies. (computer vision, dead reckoning, etc.), and positioning technology combined with GNSS and wireless positioning (A-GPS or A-GNSS). Indoor GPS Positioning Technology GPS is currently the most widely used positioning technology. When the GPS receiver is working indoors, the signal is greatly attenuated due to the influence of the building, and the positioning accuracy is also very low. It is impossible to obtain the navigation data and time information directly from the satellite broadcasting as it is outdoors. In order to obtain a higher signal sensitivity, it is necessary to extend the dwell time at each code delay. A-GPS technology offers possibilities for solving this problem. Indoor GPS technology uses a large number of correlators to search for possible delay codes in parallel, and it also helps to achieve fast positioning. The advantage of using GPS for positioning is that the satellite has a large effective coverage and the positioning and navigation signals are free. The disadvantage is that the positioning signal is weak when reaching the ground and cannot penetrate the building, and the cost of the locator terminal is high. Indoor wireless Positioning Technology With the development of wireless communication technologies, emerging wireless network technologies such as WiFi, ZigBee, Bluetooth, and ultra-wideband have been widely used in offices, homes, and factories. Infrared indoor positioning technology Infrared indoor positioning technology is based on the principle of positioning, infrared infrared emission infrared radiation identification, through the installation of optical sensors in the indoor location. Although infrared rays have a relatively high indoor positioning accuracy, infrared rays can only propagate in the line of sight because light cannot pass through obstacles. The two major drawbacks of straight line-of-sight and short transmission distance make the indoor positioning effect poor. When the logo is placed in a pocket or there is a wall or other cover, it cannot work properly. It is necessary to install a receiving antenna in each room and hallway, and the cost is high. Therefore, infrared light is only suitable for short-distance transmission, and is easily disturbed by fluorescent lights or room lights, and has limitations in precise positioning. Ultrasonic positioning technology Ultrasonic distance measurement mainly adopts reflective distance measurement method, and the position of the object is determined by triangulation and other algorithms, that is, the ultrasonic wave is transmitted and the echo generated by the measured object is received, and the distance to be measured is calculated according to the time difference between the echo and the transmitted wave. The one-way distance measurement method is used. The ultrasonic positioning system can consist of a number of transponders and a main ranger. The main ranger is placed on the object to be measured, and a radio signal with the same frequency is transmitted to a transponder with a fixed position under the action of a microcomputer command signal. The transponder is After receiving the radio signal, an ultrasonic signal is transmitted to the main ranger at the same time, and the distance between the main ranger and each transponder is obtained. When there are 3 or more transponders not on the same line responding at the same time, the position under the two-dimensional coordinate system where the measured object is located can be determined according to the relevant calculation. The overall positioning accuracy of ultrasonic positioning is high and the structure is simple. However, ultrasonic waves are greatly influenced by multi-path effects and non-line-of-sight propagation, and at the same time, a large amount of investment in the underlying hardware facilities is required, and the cost is too high. Bluetooth technology Bluetooth technology locates by measuring signal strength. This is a short-distance and low-power wireless transmission technology. It installs appropriate Bluetooth LAN access points indoors, configures the network as a multi-user based network connection mode, and ensures that the Bluetooth LAN access point is always a piconet. The master device (piconet) can obtain the user's location information. Bluetooth technology is mainly used for small-scale positioning, such as single-story halls or warehouses. The biggest advantage of Bluetooth indoor positioning technology is that the device is small and easy to integrate in PDAs, PCs, and mobile phones, so it is easy to popularize. In theory, for a user who holds a Bluetooth-enabled mobile terminal device, as long as the Bluetooth function of the device is turned on, the Bluetooth indoor positioning system can determine its position. When using this technology for indoor short-distance positioning, it is easy to discover the device and the signal transmission is not affected by the line-of-sight. The disadvantage is that the price of Bluetooth devices and devices is relatively expensive, and for a complex space environment, the stability of the Bluetooth system is somewhat poor and is greatly interfered by noise signals. Radio Frequency Identification Technology Radio frequency identification technology uses radio frequency to conduct non-contact two-way communication to exchange data for identification and positioning purposes. This technology has a short range of action, typically a maximum of tens of meters. However, it can obtain centimeter level positioning accuracy information in a few milliseconds, and the transmission range is large and the cost is low. At the same time, due to its advantages such as non-contact and non-line of sight, it is expected to become the preferred indoor positioning technology. At present, the hotspots and difficulties in the research of radio frequency identification lie in the establishment of theoretical communication models, user security and privacy, and international standardization. The advantage is that the volume of the logo is relatively small, the cost is relatively low, but the effect is close, there is no communication capability, and it is not easy to integrate into other systems. Ultra-wideband technology Ultra-wideband technology is a new kind of communication technology that is very different from traditional communication technologies. It does not need to use the carrier in the traditional communication system, but transmits and receives data by transmitting and receiving extremely narrow pulses with nanoseconds or nanoseconds or less, thereby having a bandwidth of the order of GHz. Ultra-wideband can be used for indoor precise positioning, such as position detection of battlefield soldiers, robot motion tracking, and so on. Compared with the traditional narrowband systems, the UWB system has the advantages of strong penetration, low power consumption, good anti-multipath effect, high security, low system complexity, and precision positioning accuracy. Therefore, UWB technology can be applied to indoor stationary or moving objects and people's location tracking and navigation, and can provide very accurate positioning accuracy. Wi-Fi technology Wireless local area network (WLAN) is a brand-new information acquisition platform, which can realize complex and large-scale positioning, monitoring and tracking tasks in a wide range of application areas. The positioning of network nodes is the basis and prerequisite for most applications. The current popular Wi-Fi positioning is a positioning solution of the IEEE802.11 standard of the wireless local area network series. The system uses a combination of empirical testing and signal propagation models. It is easy to install, requires few base stations, can use the same underlying wireless network structure, and has a high total system accuracy. Finland's Ekahau has developed software that can use Wi-Fi for indoor positioning. The Wi-Fi plot accuracy is in the range of about 1 to 20 meters. Overall, it is more accurate than the cellular network triangulation positioning method. However, if the positioning measurement depends only on which Wi-Fi access point is closest, rather than relying on the synthesized signal strength map, then it is easy to make mistakes in floor positioning. At present, it is applied to a small-scale indoor positioning and has a low cost. However, whether it is used for indoor or outdoor positioning, Wi-Fi transceivers can only cover the area within a radius of 90 meters, and it is easily interfered with by other signals, thus affecting the accuracy, and the energy consumption of the positioner is also high. ZigBee technology ZigBee is an emerging short-range, low-rate wireless network technology that is interposed between radio frequency identification and Bluetooth and can also be used for indoor positioning. It has its own radio standard and coordinates communication among thousands of tiny sensors to achieve positioning. These sensors require only a small amount of energy to transmit data from one sensor to another by radio waves in a relaying manner, so their communication efficiency is very high. The most significant technical feature of ZigBee is its low power consumption and low cost. In addition to the positioning technologies mentioned above, there are also computer vision, light tracking and positioning, image analysis, magnetic fields, and beacon positioning. In addition, there are positioning techniques based on image analysis, beacon positioning, and triangulation. At present, many technologies are still in the research and experimental stage, such as positioning technology based on magnetic field pressure sensing. Whether it is GPS positioning technology or the use of wireless sensor networks or other positioning means for positioning has its limitations. The trend of future indoor positioning technology is the combination of satellite navigation technology and wireless positioning technology. Combining GPS positioning technology with wireless positioning technology and exerting their respective advantages, it can provide better accuracy and response speed, and can also cover more Extensive scope for seamless, accurate positioning. Tin Zinc Antimony Copper Alloy Wire
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