Research On Low-complexity Direction Measurement Technology Based On WiFi Channel State Information

With the widespread deployment of WiFi devices in daily life,the WiFi positioning technology is favored by researchers.In the WiFi indoor positioning scheme,the positioning method of fingerprint and geometric orientation measurement is mainly adopted.Fingerprints need to collect a large amount of data,and the later maintenance is complicated.The geometric orientation is mainly divided into the methods of ranging and direction measurement.Among them,the ranging method based on Received Signal Strength Indication(RSSI)is limited by the influence of multipath effects,and the positioning accuracy is low.This article studies the WiFi indoor positioning problem from the perspective of WiFi direction measurement.At present,WiFi direction measurement usually requires the construction of a multi-antenna array,and the target orientation is calculated by performing array signal processing(such as MUSIC algorithm)on the channel state information(CSI)of the WiFi signal obtained by multiple radio frequency channels.The array signal processing method is very sensitive to the signal phase accuracy of the collected radio frequency channel.Because the CSI phase obtained directly from the commercial network card has a large error,in the process of array signal processing,people often use expensive dedicated WiFi multi-antenna array direction measurement equipment.In addition,WiFi direction measurement based on array signal processing often requires complicated calculation overhead,which further increases the cost of the equipment.This paper proposes a WiFi direction measurement solution based on lightweight hardware.This solution makes full use of the different physical characteristics of directional antennas in response to WiFi signals in different directions,and collects and learns WiFi CSI signals in different directions through a novel hardware design to realize the measurement of WiFi signal directions.Based on this idea,this article designs two WiFi CSI indoor direction measurement solutions:(1)One is a multi-directional antenna direction measurement solution based on the expansion of a single-channel WiFi module.This solution uses only one WiFi module(such as ESP32,which costs only 20 yuan)and multiple low-cost PCB directional antennas.Through extraction and learning The corresponding CSI data is used to complete the direction measurement task.(2)The other is a single-PCB directional antenna scanning direction measurement solution,which uses a micro motor(cost only 5 yuan)to drive the PCB directional antenna to rotate and scan,thereby obtaining more dimensional CSI measurement data and completing the direction measurement task.This article uses LongShort Term Memory(LSTM)to train and recognize the direction of the collected multidimensional CSI data,so as to learn the characteristics of the designed WiFi direction measurement hardware in different directions,and based on the characteristics Realize WiFi direction measurement task.The thesis implements the above-mentioned WiFi direction measurement hardware design and direction measurement method,and conducts a lot of experiments and tests on CSI and RSSI data in indoor multipath scenarios.Among them,the average angle estimation error based on the directional antenna array scheme is 11.25°(CSI)and 16.1°(RSSI);the average angle estimation error based on the directional antenna scanning scheme is 9.5°(CSI)and 14.3°(RSSI).