Performance Analysis of Wireless Location and Velocity Tracking of Digital Broadcast Signals Based on Extended Kalman Filter Algorithm

In order to improve the accuracy and reliability of wireless location in NLOS environment, a wireless location algorithm based on artificial neural network (ANN) is proposed for NLOS positioning error caused by non-line-of-sight (NLOS) propagation, such as occlusion and signal reflection. The mapping relationship between TOA and TDOA measurement data and coordinates is established. The connection weights of neural network are estimated as the state variables of nonlinear dynamic system. The multilayer perceptron network is trained by the real-time neural network training algorithm based on extended Kalman (EKF). Combined with the statistical characteristics of NLOS error, the state component NLOS bias estimation is modified to realize TDOA data reconstruction. Simulation and experimental data analysis show that the algorithm can effectively weaken the influence of NLOS error. The localization method does not depend on the specific NLOS error distribution, nor does it need LOS and NLOS recognition. It can significantly improve the mobile positioning accuracy.

Evaluation of Freeway Travel Speed Estimation Using Anonymous Cellphones as Probes: A Field Study in China

The high penetration rate of mobile phones among drivers and passengers indicates an opportunity for obtaining detailed information on vehicle spatial movement and estimating traffic state at a lower cost than traditional traffic monitoring techniques. In this study, we examine and assess the use of cellphones as probes to measure vehicle speeds. Network-based wireless location technology is adopted and calibrated, and the cellphone signalling data is used for traffic state estimation. Then, we introduce the relationship between the cellular network and road network, and explain how it can be used to estimate link-based average travel speed. Cellular probe-based measurements are compared with those obtained by microwave detectors for each five-minute time interval on busy road links along a freeway in Zhejiang, China, on weekdays, weekends, and holidays respectively. The analysis results show that the proposed cellphone-based system can effectively estimate travel speed on freeways with high cellphone penetration rates.

Risk-Aware Wireless Positioning in Maritime Environment

The evolution of wireless communications systems has promoted various applications that require user positions in various environments including indoor, maritime and aerial environments. This progress has also brought advanced wireless location tracking (i.e., positioning) schemes for many purposes such as military, accident prevention and facility management. In this paper, we propose a risk-aware wireless positioning scheme, where the position information is required for safety. Especially for the maritime environment, we model the risk of the user at each position as a function of location accuracy, geometry, ocean current speed and so forth. Considering the power budget of each user, we optimize the user’s wireless positioning signal frequency (i.e., the positioning signal broadcasting rate) at each position so that our positioning scheme can minimize the average risk for each user.