A Brief Discussion on RFID Positioning Algorithm and Application

In recent years, RFID technology has developed rapidly, and its applications and fields have become increasingly widespread. With the rapid development of the Internet of Things industry, there is also a constant push for innovation in RFID technology. RFID technology has also been widely used in various industries, such as museums using RFID technology for indoor positioning and unmanned interpretation. When it comes to positioning, the first thing that comes to mind is GPS positioning. However, due to the instability of GPS signals in traditional buildings and mobile phone signals indoors, mature and feasible indoor positioning technologies currently mainly include RFID technology, WIFI technology, and ZigBee technology. The latter two technologies cannot achieve the function of unmanned explanation, so some museums use RFID technology for indoor positioning and unmanned explanation.

1、 The difference between RFID positioning and GPS positioning

RFID card positioning and GPS positioning are two different types of positioning methods. RFID positioning requires frequent transmission of signals to specific targets through wireless antennas for positioning. In environments with dense antenna base stations, its area positioning has unparalleled accuracy. However, RFID positioning heavily relies on ground communication network base stations, which are now known as ground cellular mobile communication networks (public networks). Without the support of (public network) and antenna free base stations, the range of RFID is very limited and even unusable. The GPS satellite positioning system is a global satellite positioning system composed of 24 satellites in space, with low dependence on ground base stations. In outdoor situations, ground base stations are generally used to improve positioning accuracy, and positioning services can still be achieved without ground base stations, but the accuracy is not as high. Indoor environments require the use of wireless local area networks or ground base stations to assist in implementing location services.

GPS positioning first requires that the object being located has a GPS receiver on its body. RFID requires that the object being located has an RFID tag on it.  

2、 RFID positioning algorithm

The principle of RFID positioning is similar to GPS positioning. After receiving multiple reader/writer signals, RFID tags calculate their coordinates based on the signal values of each reader/writer.

In the following figure, A1-F8 is a site divided into 24 sub areas, each with a geographic coordinate. The notebook in the picture represents a device carrying RFID tags, and there are four RFID readers in the four corners of the venue, labeled as AP1-AP4. The RFID tag received signal strengths of (-40, -61, -79, -73) from four APs in the B3 area. Based on the strength of the signal value, the region in which it is located can ultimately be inferred.

Step 1

Divide a site into several areas, each with corresponding geographic coordinates.

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Step 2

Use an algorithm called "KWNN" to calculate the signal values of the four APs received by all subregions.

Step 3

When carrying RFID tags and receiving signal values from 4 APs, according to the KWNN algorithm, compare the AP signal values of each area to finally calculate the geographical coordinates and location area where one is located.

3、 Application Fields

Application 1: Prison

In order to strengthen the management of prisoners, especially real-time monitoring of their location, prisons can use wristbands" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> wristbands wristbands" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> wristbands wristbands" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> wristbands wristbands" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> wristbandss" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> RFID wristbands" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> wristbandss. The wristbands" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> wristbands is placed on the prisoner's hand and will automatically sound an alarm once removed. Through RFID positioning, prison management personnel can view the distribution of all prisoners in one video (prison GIS), while traditional video monitors cannot concentrate all prisoners in one picture. Once a prisoner carrying an RFID wristbands" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> wristbands approaches the edge of the prison, the system will automatically sound an alarm. Prison guards can quickly locate the prisoner based on the RFID positioning system to prevent them from escaping; In addition, if the prisoner is in a non mobile state for a long time, the system will prompt the prison authorities to check whether the prisoner is suffering from abnormal illness or forcibly opening the wristbands" target="_blank" style="margin: 0px; padding: 0px; color: rgb(0, 122, 255); text-decoration-line: none;"> wristbands to prepare for escape. When a prisoner attempts to make up, hide, or forcefully pass through the prison gate, the reader reads the wrist tag signal of illegal entry into the area and sends an alarm prompt to the central control room in the background, while the camera actively captures the scene. The central control room broadcasts real-time messages to the area through the intercom.

Application 2: Museums

Some museums are designed with irregular structures, making it easy for visitors to get lost or difficult to find the desired area to visit. Through GIS modeling and RFID navigation, visitors can carry PDA devices with integrated RFID chips to navigate within the museum, quickly finding the location and route of a certain exhibit.

Application 3: Underground Mining Sites

Due to its strong signal penetration and anti-interference ability, RFID is suitable for various complex places, so it is also used for mine management. In the mining industry, due to the complex underground environment, landslides are prone to occur. Once a landslide occurs, it takes some time for the mining company to know who has gone underground. However, the location of the miners is not clear, so once a mining accident occurs, the rescue efficiency is low because it is unclear where the underground workers are located. After using the RFID system, underground absenteeism can be located, and in case of a disaster, targeted and rapid rescue can be carried out.