Iterative Weighted Least Square Localization Algorithm in Wireless Sensor Networks
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摘要: 物联网应用的快速发展,带来了对无线定位的广泛需求,但非视距(NLOS)传输环境对无线定位方法精度具有巨大影响。因此该文基于到达时间(TOA)测量与双静态节点组合定义了一种位置残差,并据此提出运用迭代加权最小二乘(IWLS)原理的无线定位算法。算法在当前WLS定位结果基础上,通过计算位置残差获得反映NLOS严重程度的权值向量,利用权值向量在下一次WLS估计中限制NLOS影响,产生更加精确的定位结果。在算法的执行过程中,残差-权值计算方式和NLOS测距数量都会影响定位性能,因此论文通过仿真分析了这些因素对于均方根误差(RMSE)和累计概率密度函数(CDF)的影响,确定了算法的最优参数设定。最后论文对比了IWLS算法和传统定位算法的性能,仿真结果表明,在典型非视距传输环境下,该文提出的IWLS算法性能优于传统算法。Abstract:
Objective Wireless positioning technology has gained increasing attention in the Internet of Things (IoT), Intelligent Transportation Systems (ITS), and Location-Based Services (LBS). However, Non-Line-of-Sight (NLOS) errors remain a major obstacle to positioning accuracy. When Line-of-Sight (LOS) propagation between mobile and static sensors is blocked by obstacles, ranging measurement errors increase substantially. Suppressing or mitigating NLOS errors is therefore essential for improving wireless positioning performance. Although existing approaches—such as Kalman filtering, hybrid Time Difference of Arrival (TDOA)/Angle of Arrival (AOA) algorithms, and reinforcement learning—have shown some effectiveness, each faces limitations. Algorithm performance can be affected by network topology, lack adaptability in complex environments, or require high computational costs. Moreover, the statistical behavior of NLOS errors remains poorly characterized, making accurate positioning difficult in large-scale settings. This study proposes an Iterative Weighted Least Squares (IWLS) algorithm based on Time of Arrival (TOA) measurements. By defining position residuals and incorporating a residual-based weighting strategy into the WLS framework, the method suppresses NLOS errors effectively. Compared with traditional approaches, the proposed algorithm achieves higher positioning accuracy and better adaptability in NLOS scenarios, while retaining the ease of implementation offered by TOA-based techniques. Methods This study defines a new position residual based on TOA measurements from two Mobile Sensors (MSs). The residual typically approaches zero under LOS conditions but tends to increase significantly under NLOS conditions. As this residual effectively reflects deviations induced by NLOS errors, it is used to assign weights to individual equations within the linear positioning system. A residual-based weighting strategy is proposed, in which each weight is computed from the corresponding position residual, and the Weighted Least Squares (WLS) method is applied to regulate the influence of each equation. The position is estimated by iteratively updating the residuals, computing the associated weights, and applying WLS, thereby progressively reducing the positioning error and yielding an accurate estimate of the MS location. Results and Discussions The performance of the proposed algorithm is evaluated through computer simulations under varying Signal-to-Diffraction Ratio (SDR) and maximum NLOS error (NLOSmax) conditions. The simulation results indicate the following: (1) When the number of NLOS-affected static nodes is two, the Cumulative Distribution Function (CDF) of positioning error for the proposed IWLS algorithm is below 92%@5m, outperforming other tested algorithms and maintaining a consistent advantage ( Fig. 6 ). (2) In the NLOSmax scenario (Fig. 7 ), the IWLS algorithm achieves better positioning accuracy than conventional methods when the number of NLOS-affected nodes is small. As this number increases, the error of the proposed algorithm grows more gradually. (3) In the SDR scenario (Fig. 8 ), although all algorithms show degraded performance as SDR increases, the IWLS algorithm consistently yields the lowest Root Mean Square Error (RMSE) and remains closest to the Cramér-Rao Lower Bound (CRLB).Conclusions This study proposes an IWLS localization algorithm inspired by the relationship between position residuals and the reliability of localization equations. A position residual is defined using range measurements from two static sensors, and a residual-based weighting strategy is developed to suppress the influence of NLOS errors. During each iteration, the weighting vector downregulates the contribution of equations affected by large NLOS errors, thereby improving positioning accuracy. Simulation results show that the IWLS algorithm outperforms conventional localization methods under NLOS conditions and achieves RMSE values close to the CRLB. Notably, when two static sensors are affected by NLOS errors, the localization RMSE can be reduced to approximately 2 m, representing 2% of the coverage radius. -
表 1 对比方法描述
对比方法 描述 chan YT Chan提出的TS-WLS定位算法[25] $2{\text{SS-R}}$ 本文提出的位置残差倒数的1次幂 $2{\text{SS-}} {{\mathrm{R}}^2}$ 本文提出的位置残差倒数的2次幂 $2{\text{SS-}}{{\mathrm{R}}^3}$ 本文提出的位置残差倒数的3次幂 -
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