基于时间反转的室内射频定位方法评估

提出一种种基于时间反转的室内多散射环境射频定位方法.不同于传统的对多径效应敏感的采用接收信号强度、到达时间估计、到达角估计的射频定位方法,时间反转方法充分利用了多径传输作为有用信息.该方法首先要求RFID标签发射一个定位脉冲,该脉冲经过环境散射与多径传播后被阵元间距为3倍波长的稀疏天线阵接收.利用电磁场数值计算方法在仿真空间内将接收到的信号进行时间反转并重新在接收天线阵元位置分别发射.由于室内环境分布（如房间、门等）可视为已知信息,利用该信息可在仿真空间内建立完整而准确的电磁波多径传播模型,用于反演时间反转定位脉冲信号的传播过程.为了估计目标的位置,给出了基于时间反转的反演估计算子.通过监测估计子或时空域电磁场能量分布,即可获得RFID所在位置.仿真结果证实了该方法的有效性,并且由于时间反转方法充分利用了多径传输过程,故在稀疏天线阵下同样有很好的定位性能.

Evaluation of the Indoor Time-Reversal Based RF Locating Method

An indoor Time-Reversal (TR) Based RF locating method is proposed to locate a RFID tag in rich scattering environment. Unlike the conventional locating methods based on Received Signal Strength Indicator (RSSI), Time of Arrival (TOA), and Direction of Arrival (DOA) estimation which are sensitive to the multipath effects, TR method utilizes the multipath propagations as useful information. The proposed method first requests a RFID tag to emit a locating pulse, the scattered pulse is received by a sparse antenna array with 3 wavelengths spacing, and then the received signals are time-reversed and retransmitted in a simulation domain by using numerical electromagnetic calculation methods. Because the information of the environment (such as rooms, doors, et al) can be known in advance, the propagation paths of the pulse can be accurately reconstructed. In order to locate the RFID tag, a location estimator based on TR inversion is also given. By monitoring the output of this location estimator or the energy distribution in both time and spatial domains, the RFID tag can be located. This TR based RF locating method has great advantages over the traditional back-projection method because the multipath propagations in this rich scattering environment have been well utilized. Simulation results show the effectiveness of the proposed method. Furthermore, originating from the well utilization of multipath propagations, TR based method can still work very well for locating with this very sparse array.