rfid indoor personnel positioning system solution,NFC Animals

　　rfid indoor personnel positioning system solution

　　Indoor positioning technology solutions

　　1. Principle of indoor positioning system

　　Domestic conventional positioning technologies include Wifi positioning, RFID positioning, Bluetooth positioning, Zigbee positioning and other methods. What are the differences between these positioning methods and their advantages and disadvantages? Below we will analyze these positioning principles, advantages and disadvantages in detail. Your organization's reference.

　　First of all, we have to make it clear that Wifi positioning, RFID positioning, and Bluetooth positioning are just different data transmission methods. The user selects the wifi positioning tag and calls it wifi positioning, selects the RFID positioning tag and calls it RFID positioning, and selects the bluetooth ibeacon tag and calls it Bluetooth positioning. Here we focus on the positioning principle and positioning advantages and disadvantages analysis of Wifi positioning, RFID positioning, Bluetooth positioning. The effect of positioning depends on the positioning algorithm of the back-end core, and the front-end is only a difference in the way of data transmission. At present, the commonly used positioning methods for indoor positioning are mainly divided into seven types in principle: proximity detection method, centroid positioning method, multilateral positioning method, triangulation positioning method, pole method, fingerprint positioning method and dead reckoning method.

　　Different indoor positioning methods select different observation quantities, and extract the information required by the algorithm through different observation quantities. The table below provides a brief introduction to the main observations.

　　According to the positioning principles and observations introduced above, a variety of indoor positioning technologies have been derived. The following will briefly introduce the mainstream indoor positioning technologies.

　　1. WiFi positioning technology

　　At present, WiFi is a relatively mature and widely used technology. In recent years, many companies have invested in this field. There are two main types of WiFi indoor positioning technologies. WiFi positioning generally uses the "nearest neighbor method" to determine which hotspot or base station is closest to, that is, where it is considered to be. If there are multiple sources nearby, cross positioning (triangulation) can be used to improve positioning accuracy.

　　Since WiFi has become popular, there is no need to lay special equipment for positioning. Users who have turned on Wi-Fi and mobile cellular networks when using smartphones may become data sources. The technology is the first to scale due to its easy scalability, automatic data updating, and low cost.

　　However, WiFi hotspots are greatly affected by the surrounding environment and have lower accuracy. In order to be more accurate, some companies have done WiFi fingerprint collection, recorded the signal strength of a huge number of determined location points in advance, and determined the location by comparing the signal strength of the newly added device with the database with huge amount of data.

　　Since the collection work requires a large number of personnel and needs to be regularly maintained, the technology is difficult to expand. Few companies can regularly update the fingerprint data of so many shopping malls in China. In particular, data collection is greatly affected by the environment, especially for personnel positioning. Due to the large environmental changes, the phenomenon of positioning drift is particularly serious.

　　Wifi positioning pain points:

　　WiFi positioning can realize complex and large-scale positioning, which is convenient for networking, and it is easy to set up in the existing wireless WiFi network. WiFi positioning can be used in medical institutions, theme parks, factories, shopping malls and other occasions that require positioning and navigation. Wifi positioning pain points also obviously exist, mainly in the following aspects:

　　1) The wifi label used for wifi positioning is a non-standard design, but the data format refers to the 802.11b format, and does not support the standard wifi protocol. The wireless router does not support the function of scanning wifi tags, so it is necessary to develop the router twice, that is, load the wifi tag scanning firmware on the router. Some wireless routers support the wifi scanning function, which can obtain the MAC address of the wifi label, but other functions defined by the wifi label are not supported. Such as wireless sensing, button call, low battery alarm, etc. These are non-standard protocols, and standardized routers do not support non-standard protocols.

　　2) The power consumption of wifi tags is relatively large, and the continuous emission current is more than 200ma. The battery life limits the popularization and use of wifi positioning tags.

　　3) The cost of wifi tags is relatively high, which is not conducive to large-scale commercialization.

　　4) There is a serious co-channel interference problem in wifi positioning, and the systems will affect each other.

　　2. RFID positioning

　　The basic principle of RFID positioning is to read the characteristic information (such as identity ID, received signal strength, etc.) of the target RFID tag through a set of fixed readers, and the nearest neighbor method, multilateral positioning method, received signal strength and other methods can also be used to determine the tag. location.

　　This technology has a short range of action, generally up to tens of meters. But it can get centimeter-level positioning accuracy information within a few milliseconds, and has a large transmission range and low cost. At the same time, due to its non-contact and non-line-of-sight advantages, it is expected to become the preferred indoor positioning technology.

　　At present, the hotspots and difficulties of RFID research lie in the establishment of theoretical propagation models, user security and privacy, and international standardization. The advantage is that the size of the logo is relatively small and the cost is relatively low, but the operating distance is short, it does not have communication capabilities, and it is not easy to integrate into other systems, and it cannot achieve accurate positioning. The layout of the card reader and antenna requires a lot of engineering practice. Experience is difficult.

　　Shanghai Network Frequency successfully applied the wifi positioning technology to the active RFID positioning system, focusing on solving the special problems of wifi positioning, and realizing the accurate positioning of active RFID indoors. The background positioning algorithm integrates the nearest neighbor positioning method, the multilateral positioning method, the triangular positioning method, the fingerprint positioning method, and the path trajectory method. In particular, it is difficult to have a lot of practical engineering experience to deploy card readers and antennas for RFID positioning. Network frequency has launched wireless beacon positioning, which is not only easy to implement, but also greatly reduces equipment costs. The RFID beacon positioning method is easy to implement, low in cost, and combined with the network frequency positioning server algorithm, the positioning accuracy is much better than the traditional RFID regional positioning, and it is expected to become the preferred indoor positioning technology.

　　3. Infrared technology

　　Infrared is an electromagnetic wave with a wavelength between radio waves and visible light waves. There are mainly two specific implementation methods for infrared positioning. One is to attach an electronic tag that emits infrared rays to the positioning object, and measure the distance or angle of the signal source through multiple infrared sensors placed indoors, thereby calculating the location of the object.

　　This method is easy to achieve high accuracy in an open room, and can achieve passive positioning of infrared radiation sources, but infrared is easily blocked by obstacles, and the transmission distance is not long, so a large number of densely deployed sensors are required, resulting in high hardware. and construction costs. In addition, infrared is easily interfered by heat sources, lights, etc., resulting in a decrease in positioning accuracy and accuracy.

　　This technology is currently mainly used for passive positioning of infrared radiation sources such as aircraft, tanks, and missiles in the military, and is also used for position positioning of indoor self-propelled robots.

　　Another infrared positioning method is infrared weaving, that is, covering the space to be measured through an infrared net woven by multiple pairs of transmitters and receivers, and directly positioning the moving target.

　　The advantage of this method is that the positioning object does not need to carry any terminal or label, and it has strong concealment and is often used in the field of security. The disadvantage is that to achieve high-precision positioning, a large number of infrared receivers and transmitters need to be deployed, and the cost is very high, so only high-level security will use this technology.

　　4. Ultrasonic technology

　　At present, most of the ultrasonic positioning uses the reflective ranging method. The system consists of a main rangefinder and several electronic tags. The main rangefinder can be placed on the mobile robot body, and each electronic tag is placed in a fixed position in the indoor space.

　　The positioning process is as follows: first, the host computer sends a signal of the same frequency to each electronic tag, and after receiving the electronic tag, it reflects and transmits it to the main rangefinder, so that the distance between each electronic tag and the main rangefinder can be determined, and get Positioning coordinates.

　　At present, there are two more popular technologies based on ultrasonic indoor positioning: one is the combination of ultrasonic and radio frequency technology for positioning. Since the transmission rate of the radio frequency signal is close to the speed of light, which is much higher than the rate of the radio frequency, the radio frequency signal can be used to activate the electronic tag first and then make it receive the ultrasonic signal, and use the time difference method to measure the distance. This technology has low cost, low power consumption and high precision. The other is multi-ultrasound positioning technology. This technology adopts global positioning, which can install 4 ultrasonic sensors on the mobile robot in 4 directions, divide the space to be positioned, and form coordinates by ultrasonic sensors. Getting lost.

　　Ultrasonic positioning accuracy can reach centimeter level, and the accuracy is relatively high. The defect is that the ultrasonic wave is significantly attenuated during the transmission process, which affects the effective range of its positioning.

　　5. Bluetooth technology

　　Bluetooth positioning is based on the RSSI (Received Signal Strength Indication) positioning principle. According to different positioning terminals, Bluetooth positioning methods are divided into network-side positioning and terminal-side positioning.

　　The network-side positioning system consists of terminals (mobile phones and other terminals with low-power bluetooth), bluetooth beacon nodes, bluetooth gateways, wireless local area networks and back-end data servers. The specific positioning process is:

　　1) First lay beacon and Bluetooth gateway in the area.

　　2) When the terminal enters the coverage of the beacon signal, the terminal can sense the broadcast signal of the beacon, and then calculate the RSSI value under a beacon and transmit it to the back-end data server through the Bluetooth gateway through the wifi network, and calculate it through the built-in positioning algorithm of the server. The specific location of the terminal.

　　The terminal-side positioning system consists of terminal devices (such as mobile phones embedded in SDK software packages) and beacons. Its specific positioning principle is:

　　1) First lay bluetooth beacons in the area

　　2) The beacon continuously broadcasts signals and data packets to the surroundings

　　3) When the terminal device enters the range covered by the beacon signal, it measures its RSSI value under different base stations, and then calculates the specific location through the built-in positioning algorithm of the mobile phone.

　　Terminal-side positioning is generally used for indoor positioning and navigation, precise location marketing and other user terminals; while network-side positioning is mainly used in situations such as personnel tracking and positioning, asset positioning and passenger flow analysis. The advantage of Bluetooth positioning is that it is simple to implement, and the positioning accuracy is closely related to the laying density and transmission power of Bluetooth beacons. And it is very power-saving, and can achieve power-saving purposes through deep sleep, connection-free, and simple protocols.

　　6. Inertial Navigation Technology

　　This is a pure client-side technology. It mainly uses the motion data collected by the terminal inertial sensors, such as acceleration sensors, gyroscopes, etc. to measure the speed, direction, acceleration and other information of the object. Based on the dead reckoning method, the object's location information.

　　As the walking time increases, the error of inertial navigation positioning is also accumulating. It needs an external data source with higher precision to calibrate it. Therefore, inertial navigation is generally combined with WiFi fingerprints, and the indoor position is requested through WiFi every time to correct the error generated by MEMS. This technology is also relatively mature in commercial use and has been widely used in sweeping robots.

　　7. Ultra-Wideband (UWB) positioning technology

　　Ultra-broadband technology is a new wireless communication technology emerging in recent years, which is very different from traditional communication technology. It does not need to use the carrier wave in the traditional communication system, but transmits data by sending and receiving extremely narrow pulses with a nanosecond or microsecond level, so that it has a bandwidth of the order of 3.1~10.6GHz. At present, countries including the United States, Japan, Canada, etc. are researching this technology, which has a good prospect in the field of wireless indoor positioning.

　　UWB technology is a wireless technology with high transmission rate, low transmit power, strong penetrating ability and based on extremely narrow pulse, without carrier. It is these advantages that make it obtain more accurate results in the field of indoor positioning.

　　Ultra-Wideband (UWB) positioning technology uses pre-arranged anchor nodes and bridge nodes with known positions to communicate with newly added blind nodes, and uses triangulation or "fingerprint" positioning to determine the position.

　　Ultra-broadband can be used for indoor precise positioning, such as the location of soldiers on the battlefield, robot motion tracking, etc. Compared with the traditional narrowband system, the UWB system has the advantages of strong penetration, low power consumption, good anti-interference effect, high security, low system complexity, and can provide precise positioning accuracy. Therefore, UWB technology can be applied to the positioning, tracking and navigation of indoor stationary or moving objects and people, and can provide very precise positioning accuracy. Depending on the technical means or algorithms used by different companies, the accuracy can be maintained at 0.1 m~0.5 m.

　　In addition to the above, there are dozens or even hundreds of types of positioning technologies, and each positioning technology has its own advantages and disadvantages and suitable application scenarios, and there is no absolute winner. It is the best policy to deploy solutions according to different needs.

　　After the system adopts the wireless beacon locator, it not only makes the project implementation and maintenance more convenient, but also greatly reduces the equipment cost. If the user needs to improve the positioning accuracy, he only needs to appropriately increase the positioning beacon. The background uses a precise algorithm based on signal strength triangulation to locate RFID personnel and assets. The characteristics of this system are that the electronic system has low complexity, easy implementation and low cost; high positioning accuracy and strong anti-interference ability. The system can be used for wifi indoor positioning, RFID indoor positioning, Bluetooth indoor positioning and Zigbee indoor positioning.

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