High-precision indoor Wi-Fi positioning system based on OFDM channel state information phase change characteristics

Abstract

The invention discloses a high-precision indoor WiFi positioning system based on the phase change characteristics of OFDM channel state information. The main equipment of the system is composed of a wireless AP running a CSI signal feature acquisition program and a positioning server running a positioning algorithm. The wireless AP module is in On the basis of ordinary wireless AP, it can extract the CSI characteristic information between the remote wireless device and the AP wireless channel in the wireless communication process, and send the relevant information to the positioning server through high-speed Ethernet; the positioning server runs the positioning algorithm, and the The CSI feature information is transformed into the location information of the mobile device to be located. In the present invention, by extracting the channel state information in the communication process, based on the phase change characteristics of the channel state information between each OFDM sub-carrier, the high-precision indoor real-time positioning problem under indoor conditions is satisfied, which meets the actual use Require.

Description

technical field [0001] The invention relates to a high-precision indoor WiFi positioning system based on phase change characteristics of OFDM channel state information, and belongs to the technical fields of indoor navigation, object positioning and VR glasses tracking. Background technique [0002] (1) OFDM: Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing, a relatively popular wireless communication technology, widely used in the communication process of mobile devices such as PCs and mobile phones; (2) Channel state information: Channel State Information, CSI. Compared with RSSI, it is a more fine-grained representation method to describe the channel response characteristics in the wireless communication process. It usually includes time-domain CIR (channel impulse response) and CFR (channel frequency response), where CFR also includes amplitude-frequency characteristics and phase-frequency characteristics. [0003] The positioning ...

AI Technical Summary

Problems solved by technology

The main defects of this type of positioning method are: (1) Due to the propagation time delay, it is required to have extremely high-precision time synchronization between the devices used (2) The resolution and accuracy of the ADC and DAC in the device are very high (3) In the case of indoor multipath, it is difficult to distinguish the direct path, resulting in failure of positioning

The main defects of this type of method are: (1) The fingerprint construction steps are relatively cumbersome, requiring personnel to carry out signal acquisition in a carpet manner in the area (2) The collected signal fingerprints are easily affected by weather, temperature and background environment, resulting in positioning Failure (3) The distribution of wireless signals in the indoor environment is not continuous, resulting in accurate positioning at point A or point B, but unable to locate the position between A and B

[0005] To sum up, (1) GPS positioning system cannot achieve indoor positioning because satellite signals cannot penetrate thicker walls; (2) The positioning accuracy of mobile base stations based on GSM / GPRS is not high, and it is vulnerable Restricted by communication operators; (3) The positioning system based on Bluetooth, Zigbee and other signals needs to purchase special equipment, and the positioning method is based on the received signal strength RSSI, and the accuracy is not high; (4) Ordinary positioning methods based on WiFi signals do not require special equipment. However, it is usually based on the received signal strength RSSI, and the accuracy is limited; (5) the positioning system based on the channel state information in the WiFi communication process is based on the amplitude characteristics in the CSI, and relies on estimating the WiFi signal propagation attenuation model, this model It is greatly affected by the indoor environment and needs to be corrected, and the accuracy is not high

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