Positioning technology of indoor positioning

In addition to cellular positioning technology of communication network, common indoor wireless positioning technologies include Wi-Fi, Bluetooth, infrared, ultra-wideband, RFID, ZigBee, ultrasonic and so on.

L wireless network technology

Wireless local area network composed of wireless access points (including wireless routers) can realize the tasks of positioning, monitoring and tracking in complex environment. Based on the location information of network nodes (wireless access points), it uses the method of combining empirical test and signal propagation model to locate the accessed mobile devices, and the highest accuracy is about 1 meter to 20 meters. If the positioning calculation is only based on the currently connected Wi-Fi access point, instead of referring to the signal strength composite map of the surrounding Wi-Fi, there will be errors in Wi-Fi positioning (such as floor positioning errors).

In addition, Wi-Fi access points usually only cover an area with a radius of about 90 meters, which is easily interfered by other signals, thus affecting its accuracy, and the energy consumption of locators is also high.

L bluetooth technology

Bluetooth communication is a wireless transmission technology with short distance and low power consumption. After installing a suitable Bluetooth LAN access point indoors, the network will be configured as a basic network connection mode based on multi-users, and the Bluetooth LAN access point will always be the main equipment of this mini-network. In this way, the location information of the user can be obtained by detecting the signal strength.

Bluetooth positioning is mainly used for small-scale positioning, such as single-story halls or warehouses. For the mobile terminal device with integrated Bluetooth function, the Bluetooth indoor positioning system can judge its position as long as the Bluetooth function of the device is turned on.

However, for the complex space environment, the stability of Bluetooth positioning system is slightly poor, and it is greatly interfered by noise signals.

L infrared technology

Infrared technology indoor positioning is to receive modulated infrared rays (infrared IR signs) emitted by various mobile devices through optical sensors installed indoors, which has relatively high indoor positioning accuracy.

However, because light can't pass through obstacles, infrared rays can only spread in sight, which is easily interfered by other light rays, and the short transmission distance of infrared rays makes its indoor positioning effect very poor. When the mobile device is put in the pocket or blocked by the wall, it can't work normally, so it is necessary to install a receiving antenna in every room and corridor, which leads to higher overall cost.

L ultra-wideband technology

The positioning mode of UWB technology is very different from that of traditional communication technology. It does not need to use the carrier wave in the traditional communication system, but transmits data by sending and receiving very narrow pulses of nanosecond or less, which can be used for indoor accurate positioning, such as soldiers' position discovery in the battlefield, robot motion tracking and so on.

Compared with the traditional narrowband system, UWB system has the advantages of strong penetration, low power consumption, good anti-multipath effect, high security, low system complexity, and improved accurate positioning accuracy. It is usually used to locate, track or navigate indoor moving objects.

L RFID technology

RFID positioning technology uses radio frequency to exchange data in a non-contact two-way communication way to realize the purpose of mobile device identification and positioning. The information of centimeter-level positioning accuracy can be obtained in a few milliseconds, with large transmission range and low cost. However, due to the following problems, the application scope of RFID positioning technology is limited.

1.RFID is not easy to integrate into mobile devices.

2. The action distance is short (generally the longest is tens of meters)

3. User safety and privacy protection

4. International standardization

zigbee technology

ZigBee is a short-distance and low-rate wireless network technology. It is between RFID and Bluetooth, and locates the position of equipment through coordinated communication between sensors. These sensors only need a little energy, and transmit data from one sensor to another by relay through radio waves, so the most remarkable technical characteristics of ZigBee are low power consumption and low cost.

L ultrasonic technology

Ultrasonic positioning mainly adopts reflective ranging (transmitting ultrasonic waves, after receiving the echo generated by the measured object, calculating the distance between them according to the time difference between the echo and the transmitted wave), and determining the position of the object through triangulation and other algorithms.

Ultrasonic positioning has high overall positioning accuracy and simple system structure, but it is easily affected by multipath effect and non-line-of-sight propagation, which reduces positioning accuracy. At the same time, it also needs a lot of investment in the underlying hardware facilities, and the overall cost is high.