Outdoor Localization System Based On LoRa Mesh

With the rapid development of Internet of Things technology,the demand for obtaining location information is constantly emerging in industries,transportation,agriculture and other fields.The outdoor wide-area positioning task requires that the positioning nodes meet the requirements of low power consumption,long endurance,and low cost,and that the positioning system be able to achieve high-precision positioning and wide-area coverage.The traditional Internet of Things positioning technology can not balance the cost,energy consumption and positioning system performance.Based on LoRa technology,a low-cost,low-power and outdoor positioning system based on multi-anchor wireless Mesh networking and multi-dimensional data fusion is designed in this thesis.The main work and contributions of this thesis are as follows:1.A LoRa Mesh protocol with low power consumption and high reliability is designed for positioning system.In view of the absence of LoRa Mesh protocol standard,a lightweight LoRa Mesh protocol stack and packet format are defined.The protocol optimizes packet congestion by channel activity detection mechanism and improves communication reliability.In order to improve networking efficiency,a multi-variable collaborative optimization routing algorithm is designed based on local routing state information of nodes.Experimental results show that this routing algorithm can take into account both delay and communication quality effectively.2.Aiming at the problem that LoRa ranging accuracy is easily affected by non-line-of-sight path propagation,a distance estimation algorithm based on the fusion of TOF and RSSI multi-sampling data is designed.Based on the TOF and RSSI data obtained by multisnap sampling,the line-of-sight channel and non-line-of-sight channel are screened by clustering idea,and the line-of-sight channel is found and the distance is estimated.Experimental results show that the average distance measurement error of this algorithm is6.46 m in complex outdoor scenes.3.A position estimation algorithm with minimum posterior RSSI error is designed for multianchor co-estimation scenarios.By calculating a posteriori RSSI error of position estimation coordinates,an evaluation criterion of position estimation results is designed.Based on this criterion,a heuristic anchor selection method is designed to reduce the interference of bad anchor points and improve the accuracy of position calculation.Experimental results in outdoor scenes show that the proposed algorithm can provide meter-level positioning accuracy when the regional anchor point density is high.4.Based on the LoRa Mesh protocol,ranging and positioning algorithm,an outdoor positioning method and system based on LoRa Mesh are designed.By optimizing the system logic of network communication and wireless location function,the localization system realizes the coexistence of both at the system level.This paper also simulates the spatial signal distribution through electromagnetic simulation to find the best anchor point deployment method to make the location signal coverage effect.On this basis,this paper designs the upper computer software and hardware platform,and sets up a demonstrable LoRa outdoor positioning system,and tests it in the campus environment.The test results show that the system can provide good location service for outdoor square kilometer area.The peak power consumption of a single device in the system is less than 120 mw,the average power consumption is less than 50 mw,and the cost is less than 100 RMB,which can meet the outdoor positioning requirements of low-power and low-cost devices.