Advantages and disadvantages of ten common positioning technologies in the Internet of Things

The era of the Internet of Everything is also the era when data is king. However, in many cases, the lack of corresponding location information means that the data is “disorganized” and the value that can be utilized is greatly reduced. With the booming development of the Internet of Things industry in the past two years, the demand for positioning technology in various IoT application scenarios has also been greatly improved. Here are a few indoor and outdoor positioning technologies.

1. Radio frequency identification indoor positioning technology

The radio frequency identification indoor positioning technology uses the radio frequency method, the fixed antenna adjusts the radio signal into an electromagnetic field, and the label attached to the article generates an induced current through the magnetic field to transmit the data, and exchanges data in multiple pairs of two-way communication to achieve the purpose of identification and triangulation.

The radio frequency identification indoor positioning technology has a very close working distance, but it can obtain centimeter-level positioning accuracy information within a few milliseconds, and because of the advantages of electromagnetic field non-line of sight, the transmission range is large, and the volume of the logo is relatively small, and the cost is relatively low. However, it does not have the communication capability, the anti-interference ability is poor, it is not easy to integrate into other systems, and the user's security privacy protection and international standardization are not perfect.

Radio frequency identification indoor positioning has been widely used in warehouses, factories, and shopping malls for cargo and commodity circulation positioning.

2, Wi-Fi indoor positioning technology

There are two kinds of Wi-Fi positioning technology. One is the wireless signal strength of the mobile device and the three wireless network access points, and the differential algorithm is used to accurately position the person and the vehicle. The other is to record a huge amount of signal strength at a certain location point in advance, and determine the location by comparing the database with the huge amount of data with the signal strength of the newly added device.

Wi-Fi positioning can realize complex large-scale positioning, monitoring and tracking tasks in a wide range of applications. The total accuracy is relatively high, but the accuracy for indoor positioning can only reach about 2 meters, which cannot be accurately positioned. Due to the popularity of Wi-Fi routers and mobile terminals, the positioning system can share the network with other customers, the hardware cost is very low, and the Wi-Fi positioning system can reduce the possibility of radio frequency (RF) interference.

Wi-Fi positioning is suitable for positioning and navigation of people or vehicles. It can be used in medical institutions, theme parks, factories, shopping malls, etc. where navigation is required.

3 , ultra-wideband (UWB) positioning technology

Ultra-wideband technology is a new communication wireless technology that has been greatly different in recent years and has great differences from traditional communication technologies. It does not need to use the carrier in the traditional communication system, but transmits data by transmitting and receiving very narrow pulses with nanoseconds or less, thus having a bandwidth of the order of 3.1 to 10.6 GHz. At present, countries including the United States, Japan, Canada, etc. are studying this technology and have good prospects in the field of wireless indoor positioning.

UWB technology is a wireless technology with high transmission rate, low transmission power, strong penetration capability and based on extremely narrow pulses, without carrier. It is these advantages that make it more accurate in the field of indoor positioning. Ultra-wideband indoor positioning technology often adopts TDOA demonstration ranging positioning algorithm, which is the radio system that generates, transmits, receives, and processes extremely narrow pulse signals by the time difference of signal arrival. Ultra-wideband indoor positioning systems include UWB receivers, UWB reference tags, and active UWB tags. During the positioning process, the UWB signal received by the UWB receiver receives the UWB signal transmitted by the tag, and the signal containing the effective information is obtained by filtering various noise interferences in the electromagnetic wave transmission process, and then the central processing unit performs the distance measurement calculation analysis.

Ultra-wideband can be used for precise indoor positioning, such as location detection of battlefield soldiers, robot motion tracking, and more. Compared with the traditional narrowband system, the ultra-wideband system has the advantages of strong penetrating power, low power consumption, good anti-interference effect, high safety, low system complexity, and accurate positioning accuracy. Therefore, UWB technology can be applied to indoor stationary or moving objects as well as human positioning tracking and navigation, and can provide very accurate positioning accuracy. The accuracy can be kept from 0.1 m to 0.5 m depending on the technical means or algorithms used by different companies.

4 , geomagnetic positioning technology

The Earth can be thought of as a magnetic dipole, with one pole near the geographic North Pole and the other near the geographic South Pole. The geomagnetic field consists of two parts: the basic magnetic field and the changing magnetic field. The basic magnetic field is the main part of the geomagnetic field. It originates from the interior of the earth and is relatively stable. It belongs to the static magnetic field. The changing magnetic field includes various short-term changes of the earth's magnetic field, which originate mainly from the interior of the earth and are relatively weak.

The reinforced concrete structure of modern buildings will disturb the geomagnetism in a local area, and the compass may be affected as well. In principle, a non-uniform magnetic field environment produces different magnetic field observations due to different paths. The positioning technology called IndoorAtlas uses the geomagnetic indoors to make indoor navigation, and the navigation accuracy can reach 0.1 meters to 2 meters.

However, the process of navigating using this technique is a little more troublesome. You need to upload the indoor floor plan to the map cloud provided by IndoorAtlas, and then you need to use its mobile client to record the geomagnetic field in different directions of the target location. The recorded geomagnetic data will be uploaded to the cloud by the client, so that others can use the recorded geomagnetic to perform precise indoor navigation.

Baidu invested in GeoAt positioning technology developer IndoorAtlas in 2014 and announced in June 2015 that it uses its geomagnetic positioning technology in its map application, which is used in conjunction with Wi-Fi hotspot maps and inertial navigation technology. High precision, in the promotion of commercial applications, can reach the meter-level positioning standard, but the magnetic signal is easily interfered by the changing electrical and magnetic signal sources in the environment, the positioning result is unstable, and the accuracy will be affected.

5 , ultrasonic positioning technology

Ultrasonic positioning technology emits ultrasonic signals that can be detected by the terminal microphone by installing a plurality of ultrasonic speakers indoors. The position of the terminal is estimated by the difference in arrival times of different sound waves.

Since the transmission speed of sound waves is much lower than that of electromagnetic waves, the system implementation is very difficult, and the wireless synchronization of the system can be realized very simply, and then transmitted by the ultrasonic transmitter, and the receiving end receives the microphone, and the operation position can be performed by itself.

Since the rate of sound waves is relatively low, it takes a long time to transmit the same content, and only a TDoA-like way can obtain a larger system capacity.

6 , ZigBee indoor positioning technology

The technology forms a network between a plurality of blind nodes to be located and a reference node of a known location and a gateway, and each tiny blind node communicates with each other to achieve complete positioning.

ZigBee is an emerging short-range, low-rate wireless network technology that requires very little energy to relay data from one node to another in a relayed manner, as a low-power and low-cost device. The communication system, ZigBee is very efficient. However, the signal transmission of ZigBee is greatly affected by multipath effect and movement, and the positioning accuracy depends on the physical quality of the channel, the density of the signal source, the accuracy of the environment and the algorithm, and the cost of the positioning software is high, and the space is still large. .

ZigBee indoor positioning has been adopted by many large factories and workshops as personnel on-the-job management systems.

7 , infrared positioning technology

Infrared is an electromagnetic wave between wavelengths of radio waves and visible waves. The principle of infrared indoor positioning technology positioning is that the infrared ray emits modulated infrared rays and is received by an optical sensor installed indoors for positioning. Although infrared rays have relatively high indoor positioning accuracy, infrared rays can only be transmitted by line of sight because light cannot pass through obstacles. The two major drawbacks of linear line of sight and short transmission distance make the indoor positioning effect very poor. When the logo is placed in a pocket or has walls and other obstructions, it will not work properly. It is necessary to install a receiving antenna in each room and corridor, which is expensive. Therefore, infrared rays are only suitable for short-distance propagation, and are easily interfered by fluorescent lamps or lights in a room, and have limitations in precise positioning.

The typical infrared indoor positioning system Activebadges attaches an electronic target to the object to be tested. The identifier transmits the unique ID of the object to be tested periodically through the infrared transmitter to the infrared receiver fixedly placed indoors, and the receiver transmits the data to the wired network. database. This positioning technology consumes a lot of power and is often blocked by indoor walls or objects, and is less practical. The positioning function can be easily realized by combining infrared and ultrasonic technology. The infrared ray is used to trigger the positioning signal to make the ultrasonic transmitter of the reference point transmit ultrasonic waves to the point to be measured, and apply the TOA basic algorithm to locate the position through the timer. On the one hand, the power consumption is reduced, and on the other hand, the short-distance transmission distance of the ultrasonic reflective positioning technology is avoided. The advantages of infrared technology and ultrasonic technology are complementary.

8 , Bluetooth positioning technology

Bluetooth technology is positioned by measuring signal strength. This is a short-range, low-power wireless transmission technology that installs appropriate Bluetooth LAN access points indoors, configures the network into a multi-user based network connection mode, and ensures that the Bluetooth LAN access point is always the piconet. The (piconet) master device can obtain the user's location information. Bluetooth technology is primarily used for small-scale positioning, such as single-story halls or warehouses. The biggest advantage of Bluetooth indoor positioning technology is that it is small in size and easy to integrate in PDA, PC and mobile phone, so it is easy to popularize. In theory, for a user holding a Bluetooth-enabled mobile terminal device, the Bluetooth indoor positioning system can determine the position of the device as long as the Bluetooth function of the device is turned on. When this technology is used for indoor short-distance positioning, the device is easily found and the signal transmission is not affected by the line of sight. The accuracy can be maintained from 3 m to 15 m depending on the technical means or algorithms used by different companies.

9 , GPS and Beidou satellite and other positioning technologies

Beidou satellite positioning is independently developed by China and uses geosynchronous satellites to provide users with an all-weather, regional satellite positioning system. It can quickly determine the location of the target or user and provide navigation information to users and authorities.

The Beidou satellite navigation system played an important role in the 2008 Wenchuan Earthquake disaster relief. In the case of severe damage to local communication facilities, the Beidou satellite system is used to realize the liaison between various departments at various points, and the location of each disaster relief unit can be accurately determined to timely release new rescue missions according to the disaster situation.

At present, Beidou satellites are used less in civilians, and Beidou mobile phones and Beidou car navigation can also be seen on the market.

10 , base station positioning technology

The base station location is generally applied to mobile phone users. The mobile phone base station location service is also called Location Based Service (LBS), which acquires the location information (latitude and longitude coordinates) of the mobile terminal user through the network of the telecommunication mobile operator (such as the GSM network). ), with the support of the electronic map platform, a value-added service that provides users with corresponding services, such as the dynamic location query service provided by China Mobile's M-Zone.

Since GPS positioning is relatively expensive, base station positioning is a common function of GPS devices. However, the positioning accuracy of the base station is low, generally ranging from 500 meters to 2000 meters.

In addition to the above mentioned, 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. In the end, which technology will eventually win, it is still unknown, and it is necessary to test the efforts and time of the industry chain colleagues.