An Improved Algorithm For High-precision Positioning Based On Ranging-based Wireless Sensor Networks

This paper first introduces the basic concepts of wireless sensor networks,the structure and characteristics of wireless sensor networks and some related domestic and foreign researches and applications.The node localization algorithms in wireless sensor networks are divided into two major categories: ranging-based positioning algorithms and location-free positioning algorithms.Because the low accuracy of positioning algorithms that do not require distance measurement,positioning algorithms based on distance measurement must be used to improve positioning accuracy.In practical applications,it is impossible to avoid NLOS propagation of signals.Therefore,how to eliminate the influence of NLOS errors on positioning has become one of the most important and the core problem in wireless sensor network positioning.This paper will focus on the location-based location algorithm in NLOS environments after analyzing the location algorithm that needs to be measured.Through the introduction of the commonly measuring principle based on ranging technology positioning algorithm,the calculation formulae are deduced,the factors affecting the positioning accuracy based on distance measurement are discussed,the error of the distance measurement value is summarized,the characteristics of NLOS error are analyzed,and methods for reducing its impact,including traditional residual detection and localization algorithms are described.The traditional residual detection and localization algorithm needs to traverse all the packets.It will be a large amount of calculation when the number of available sensor nodes is large and the time-consuming will be too long,which is not conducive to practical applications.With the large amount of calculation under the premise of ensuring a certain positioning accuracy,the traditional residual detection algorithm has too much computational complexity.This paper proposes a innovative dedicated improved residual detection algorithm.The algorithm first divides the distance measurement values into groups of four,uses the distance measurement values of the three nodes in the sub-group with the smallest residual error,and then selects an uncalculated node distance measurement value to be combined to detect whether NLOS signal is included.The line-of-sight signal will be selected by repeating this step.Considering an algorithm based on the time-of-arrival(TOA)of a signal,only three signals from the line-of-sight propagation need to be determined.It is not necessary to select all the line-of-sight signals.The algorithm avoids the calculation of packets containing NLOS signals and reduces the amount of computation.To accurate measurement time,triggers the transmitter to emit radio waves under the control of the ARM.By changing the delay circuit time,the received return signal arrives at the same time as the delay time signal.It can be considered that the time from transmission to reception of radio waves is equivalent to the total time of delay.The delay time of 10 ns is measured with an ARM clock sync of 100 MHz;the delay time of 50 ps is measured with a programmable delay chip,which achieves a measurement time accuracy of 50 ps,thus achieving a measurement distance accuracy of 1.5cm.In this paper,the optimized residual detection algorithm can be used to determine the line-of-sight signal.Combining with the principle of accurately measuring the arrival time of the signal,the hardware and corresponding software for accurately measuring the arrival time of the signal are designed and the mutual communication protocol is established.By using the new improved algorithm,this paper experimentally measures the target location in the NLOS environment and verifies the positioning accuracy is within 1.5cm,the measurement error is 1.5cm,and the computational complexity of the new algorithm is greatly reduced.It can be applied in an uncomplicated real environment.