| Localization and tracking based on wireless sensor network is an emerging technique in recent years, which has wide applications in areas like security, smart home, disaster relief and environmental protection. Among methods in this field, device-free motion tracking methods, which donot require the target to carry any transmitting and receiving devices, are highly favored as its larger scope of application.This paper presents a novel device-free motion tracking (DFMT) system using an RF sensor network with very few nodes. The system includes a newly designed measurement model and corresponding tracking algorithm, which can calculate the moving path of target with received signal strengths(RSS) of links between sensor nodes.Based on the uniform theory of diffraction (UTD), we prove that the received signal strength (RSS) measurements can be separated into two parts, which are named "diffracted waves" and "scattered waves" separately. Changes on power of these two parts of components reflecting the shadowing and scattering effects on the electromagnitive waves cause by the target.Then we derived two measurement named "long term measurement" and " short term measurement" based on the two types of multipath components. Then a model considering both two measurements is proposed to obtain relative positions between target and every single link using RSS measurements. The new model expands sensing range of each wireless link.Particle filtering algorithm is then applied to perform tracking, along with Markov jumping state model to get prior information and onlineEM algorithm to evaluate parameters in realtime.We develop a experiment platform with CC2530wireless transceiving chips as key parts to test our tracking system. Experiment results illustrate that this tracking system has a hign updating rate and accurate tracking results with very few nodes in different scenarios. |
PDF Full Text Request