Analysis of the advantages and disadvantages of indoor positioning technologies such as RFID and UWB

In the context of the Internet of Everything, the market has more and more demand for positioning, so various positioning technologies have also been derived. As we all know, GPS is the most common positioning technology at present, but it has an obvious defect, that is, its shortcoming in indoor positioning, and the accuracy of general civilian use is not high enough to meet the requirements of indoor positioning. Therefore, currently commonly used positioning technologies include: RFID, UWB, WIFI, Bluetooth, etc. Let’s discuss the advantages and disadvantages of these positioning technologies below!

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 group of Honglu fixed readers, and the nearest neighbor method, multilateral positioning method, received signal strength, etc. can also be used The method determines the location of the RFID electronic tag. The basic structure of the RFID indoor positioning system usually consists of RFID electronic tags, readers, middleware and computer databases. The system uses the "nearest neighbor" algorithm and empirical formula to calculate the coordinates of the positioning tag through the analysis and calculation of the signal strength RSSI of the reference tag and the pending tag.

Advantage :

1. The cost is very low, the cost of RFID electronic tags is low, and it can be deployed on a large scale;

2. RFID provides two schemes, active and passive. The passive scheme has no power supply problem. The active scheme can also achieve extremely low power consumption, and it can last for several years with a button battery;

3. RFID base station equipment is relatively rich, and there are many high-power equipment and low-power reader products, which are more convenient for project implementation and maintenance, and are suitable for networking in various occasions.

shortcoming:

1. RFID technology is mainly used to identify whether people exist in a certain area, and it cannot be tracked in real time;

2. The positioning accuracy is determined by the position and density of the reference tag and the UHF RFID Reader;

3. To meet the same accuracy requirements, the deployment of RFID readers is relatively complex and the number is large.

Application scenario:

RFID reading and writing equipment is relatively stable, so it is widely used in the field of positioning. It has mature applications and good prospects for use in logistics sorting, prison positioning, battery car positioning, and automotive electronic license plate positioning.

UWB positioning

In the UWB (ultra-wideband technology) positioning process, the UWB receiver receives the UWB signal transmitted by the tag, and filters the various noise interference mixed in the electromagnetic wave transmission process to obtain a signal containing effective information, and then performs distance measurement and positioning calculation through the central processing unit analyze. The TDOA algorithm is used for positioning, and the UWB positioning requires the support of 3 base stations.

Advantage:

1. It has the dual advantages of real-time positioning and precise positioning;

2. The delay time of positioning is short, and the positioning accuracy can reach about 10cm;

3. The dedicated positioning network has high reliability.

shortcoming:

1. There must be no obstacles that block radio transmission. Once the wall is blocked, it needs to be redeployed. With the same area, the number of rooms increases and the base station usage will also increase;

2. A complete positioning network is required, and any positioning point needs to be supported by three positioning base stations. The UWB positioning algorithm is based on three-point positioning. If the number of base stations is reduced, the positioning accuracy will be greatly affected;

3. UWB positioning needs to deploy a positioning network, so the cost is relatively high.

Application scenario:

UWB positioning is mainly used in industries that have relatively high requirements for real-time processes or precise positioning, such as tunnels, chemical plants, prisons, Hospitals, nursing homes, mines and other industries.

Bluetooth positioning

Bluetooth positioning is a short-distance low-power wireless transmission technology. Install an appropriate Bluetooth LAN access point indoors, configure the network as a basic network connection mode based on multi-users, and ensure that the Bluetooth LAN access point is always the piconet The master device can obtain the user's location information. The RSSI (received signal strength) mechanism is added to the data packet transmission, and the approximate range of the product is virtualized through RSSI, and then the measurement algorithm of mutual intersection is realized through the trilateration method, and the indoor positioning is finally completed.

advantage:

1. The equipment is small in size, easy to integrate into PDAs, PCs and mobile phones, and easy to popularize;

2. Bluetooth transmission is not affected by the line-of-sight, as long as the Bluetooth function of the device is turned on, it can be positioned;

shortcoming:

1. The stability of the Bluetooth system is slightly poor, and it is greatly disturbed by noise signals;

2. The price of Bluetooth devices and equipment is relatively expensive, and the cost of network maintenance is relatively high.

Application scenario:

Bluetooth terminals are mostly Bluetooth bracelets, which are mainly used in shopping mall positioning, hospital positioning, item loss prevention, shopping mall positioning, entertainment venue positioning, WeChat shake and other places, all of which are non-rigid requirements.

WIFI positioning

WIFI positioning is generally judged by the "nearest neighbor method", that is, which hotspot or base station is the closest, that is, where it is considered to be. If there are multiple sources nearby, cross positioning (triangular positioning) can be used to improve positioning accuracy. Since WiFi has become popular, there is no need to lay special equipment for positioning. When a user has turned on WIFI or mobile cellular network while using a smartphone, it may become a data source. The WIFI positioning method is based on the signal strength propagation model method and fingerprint identification method. The propagation model method of signal strength refers to using a certain channel fading model assumed in the current environment, and estimating the distance between the terminal and the known location AP according to its mathematical relationship. If the user hears multiple AP signals, they can pass the three-sided The positioning algorithm is used to obtain the user's location information; the fingerprint recognition method is based on the propagation characteristics of WiFi signals, combining the detection data of multiple APs into fingerprint information, and estimating the possible position of the moving object by comparing it with the reference data.

Advantage:

1. WIFI is widely deployed and does not require high precision. After the construction of WIFI data transmission network is completed, the WIFI positioning function can be activated by assuming the positioning engine service;

2. Mobile terminals can be used, omitting the cost of terminal deployment;

3. The cost is low. The chip module of WIFI is about 10 yuan. The price of WIFI base station and AP is less than 100 yuan, and it can perform data transmission and positioning functions, so it can meet the needs of large-scale expansion at low cost.

shortcoming:

1. Whether it is used for indoor or outdoor positioning, the WIFI transceiver can only cover an area within a radius of 90 meters;

2. The Apple mobile phone cannot be used, and Apple has not opened the corresponding interface;

3. The workload of WIFI positioning on the location map is relatively large;

4. It is easy to be interfered by other signals, thus affecting its accuracy, and the energy consumption of the locator is relatively high.

Application scenario:

WIFI positioning is mainly for low-precision scenarios, such as scenic spot positioning, large shopping mall positioning, shopping mall positioning, entertainment venue positioning, company employee WIFI attendance, WIFI sign-in, exhibition positioning, etc.

In different scenarios, when we choose a specific positioning technology, we must consider not only the accuracy performance, but also the cost and power consumption.