Research On TDOA Outdoor Positioning Based On LoRa Technology

In outdoor wireless positioning,high-precision GPS modules are currently mainly used.However,in the field of Low Power Wide Area Network(LPWAN),many Io T location applications require only coarse-precision location information.What is required is a battery-powered system that can reach several years of endurance.Obviously,the high-power consumption of GPS is difficult to meet actual needs.With the rise of LPWAN,as the main technology of Long Range(LoRa),its technical characteristics are low power consumption and long transmission distance,and its characteristics are just in line with the energy consumption and communication requirements of low-power wide area network equipment.The emergence of LoRa spread spectrum communication technology has brought new choices and inspiration to the communication and positioning problems of low-power wide area network equipment.It is a challenging thing to complete positioning at the same time based on wireless signal communication.For now,in the ea rly stage of the LPWAN field,the commercial deployment is to use LoRa as the communication technology,and GPS,sensors,etc.As the combined positioning solution of the positioning technology.The implementation is relatively simple,but the equipment cost is high,and the equipment life is up to less than realistic requirements and other issues.This paper will consider communication and positioning at the same time from the perspective of LoRa signal.Based on the data frame sent by LoRa,outdoor wireless positioning research based on Time Difference of Arrival(TDOA)will be completed.Firstly,we consulted a lot of information to understand development of LoRa and LoRa modulation technology,and combined with IEEE802.15.4a CM9 channel to simulate the LoRa outdoor communication system,and realized models including LoRa modulation,transmission,channel,and reception.Then,based on the above model,a cross-correlation(Generalized Cross Correlation,GCC)time delay estimation technique is used to estim ate the measured of the arrival,and the estimated of the measured time difference of arrival(TDOA)is further obtained.In this process,we discussed the influence of different modulation parameters of LoRa,bandwidth(BW),spreading factor(SF),and signal-to-noise ratio(SNR)on the estimation of the measured value of time.Next,we conduct research on the positioning algorithm,and perform TDOA positioning algorithm processing on the three algorithms of Chan,Taylor,and Chan-Taylor,and use different LoRa modulation parameters to understand the influence of the LoRa signal used for positioning on the positioning.Finally,we introduced the genetic algorithm(GA)in the intelligent search algorithm and its improved Chan-GA to study under different measurement noises.Through simulation,we found that the main factor that affects LoRa TDOA positioning is the accuracy of the arrival time estimation,which has little effect on the modulation parameters of LoRa.The GCC time estimation technology is adopted,and the initial value is more accurate and the measurement noise error is small.Based on Taylor algorithm,GA algorithm,and improved Chan-GA algorithm can reach within 25 m under the cumulative distribution probability of error of 90%,which can basical ly meet the requirements of most LPWAN terminal positions.In the case of large initial value errors and measurement errors,the Chan-GA algorithm can obtain better stability and positioning accuracy.