RFID-based positioning technology introduction

As one of the supporting technologies of the Internet of Things, RFID is an identification technology that does not require direct contact. It uses radio frequency signals to read and transmit information Stored in electronic tags. RFID technology has the characteristics of non-line-of-sight transmission and fast identification. The electronic tags used in RFID technology to store information have the advantages of small size, low cost, and reusability. Widely used in logistics tracking, transportation, shopping mall cargo management, item positioning and other fields.

RFID system framework:

RFID tags are divided into active and passive. Active tags can be regarded as RFID in a relatively broad sense. Since the tags themselves are active, the signal processing can also be done more complicated, and the positioning accuracy will be much higher. Ideally, it can cover a range of 100 meters, and the positioning error is about 5 meters. It is mainly completed by triangulation, but this field can also use nodes such as uwb, ZigBee, etc. to complete positioning. Passive tags refer to RFID most of the time. Since the tags themselves have no computing power, all signal processing is limited by the reflected signals received by the reader, so the choice of signal processing algorithms will be much smaller. And because the recognition range of the reader is basically within 10 meters, it is generally very fine positioning that will study the positioning of passive tags.

RFID Indoor Positioning Technology

The RFID-based indoor positioning method is to locate the tag through a reader with a known position, which can be divided into a non-ranging method and a ranging method. The method based on ranging refers to estimating the actual distance between the target device and each tag through various ranging techniques, and then estimating the position of the target device through a geometric method. Commonly used ranging-based positioning methods include: positioning based on Time of Arrival (TOA), positioning based on Time Difference of Arrival (TDOA), positioning based on RSSI, positioning based on Angle of Arrival (Angle of Arrival, AOA), etc. These technologies are consistent with the technical principles used in UWB and Wi-Fi, but the propagation distance of RFID signals is very short due to energy constraints, generally only a few meters to tens of meters away.

Non-ranging method

The non-ranging method refers to collecting the information of the scene in the early stage, and then matching the obtained target with the scene information, so as to locate the target. Typical implementation methods are the reference tag method and the fingerprint positioning method. The commonly used algorithm for the reference tag method is the centroid positioning method. The fingerprint positioning method is basically the same as that used in Wi-Fi positioning, Beacon positioning and other technologies. Arrange some readers in the positioning space. The positions of the readers are known. When the target tag enters the scene, multiple readers can read the target tag information at the same time. The positions and connections of these readers form a polygon , the centroid of this polygon can be considered as the position coordinates of the target label. The implementation steps of the centroid positioning algorithm are simple and easy to operate, but the positioning accuracy is relatively low. It is often used in scenarios where the positioning accuracy is not high and the hardware equipment is limited.

Advantages of RFID technology positioning

The advantage of the positioning method based on RFID technology lies in its low cost. The cost of active RFID tags is usually tens of yuan, while the cost of passive RFID tags can be several yuan, and the size of the tags is small, usually made into the shape of a sheet, and RFID radio frequency signal has strong penetration and can carry out non-line-of-sight communication. The communication efficiency of the RFID system is very high. Compared with Wi-Fi and Zigbee and other systems that require network access, an RFID Reader can complete the reading and writing of hundreds of tags within 1 second. Compared with ZigBee, Bluetooth and Wi-Fi wireless positioning technologies, RFID has lower node cost and faster positioning speed, but its communication capability is weaker, so RFID positioning is especially suitable for simple tagged objects, but does not require a large number of In the case of data communication.

Disadvantages of RFID technology positioning

However, the existing positioning system using RFID technology has many shortcomings, such as large positioning error, complex system deployment, and easy to be affected by the environment. For example, the positioning method based on RSS is limited by the large fluctuation of RSS itself and the sensitivity to environmental interference. It is difficult to further improve. The positioning method based on TOA and TDOA requires high accuracy of time measurement, but due to the low communication rate of the passive RFID system, it is difficult to observe the precise time. Generally speaking, the application range of RFID positioning technology is narrow, the positioning accuracy is poor, and there are few practical cases.

Geomagnetic Positioning Technology

Compared with the positioning method based on RFID technology, geomagnetic positioning does not require any hardware equipment, and the positioning target does not need to add any tags. It is suitable for any complex situation and super large indoor scenes, with high positioning accuracy. Extra maintenance at very low cost. Hangzhou Tenfield Technology is a positioning service and data service provider based on geomagnetic indoor positioning technology. It was co-founded by a number of well-known scholars at home and abroad. It has rich application functions and aims to provide users with overall solutions for digital personnel positioning systems.