基于自适应时延估计的室内近场测距算法

Indoor Near Field Ranging Algorithm Based on Adaptive Time Delay Estimation

室内近场测距利用近场区内电磁场之间的相位差与通信距离之间的关系来实现测距.但测量相位差不仅需要目标信号的先验知识,且对系统同步精度要求较高.该文将电磁场之间的相位差转化为电磁场之间的时间延迟,通过自适应时延估计来实现近场测距.SETDE算法能够在低信噪比的情况下实现时延的自适应估计,且计算开销小,适用于实时测距系统.但当时延变化快时,SETDE算法对时延的估计会存在一定的时间滞后,且有可能收敛于局部最优值,无法得到真实时延.针对这个问题,该文提出了一种改进的RSSI-SETDE算法,并通过仿真和实验测试对算法的可行性进行了验证.在现有脉冲噪声模型和传播模型的基础上,通过自适应阈值脉冲消隐器滤除脉冲噪声,计算接收信号强度,得到通信距离和电磁场时延的粗略估计,将其作为SETDE算法的初始时延估计值.在一定信噪比范围内,RSSI-SETDE算法能够避免代价函数局部最优值对时延估计的影响,提高算法的收敛速度,适用于对室内移动目标的快速跟踪测距.

The near-field phase behavior of radio signals is exploited in indoor near-field electromagnetic real-time ranging system.Phase difference detection needs not only apriori knowledge of the target signal,but also high precision of system synchronization.The phase difference between the electric and magnetic components of a narrow-band low frequency signal can be converted to the time delay between them.Accordingly,time delay estimation can be exploited in indoor near-field ranging system.Simplified explicit time delay estimator（SETDE）can adaptively track the time delay at low signal-to-noise ratio（SNR）and is computationally efficient for in indoor real-time locating system.But when time delay changes rapidly,the SETDE algorithm tracks the delays with time lags.The SETDE algorithm may not converge to the true time delay because of local optima.To address this problem,an Improved RSSI-SETDE algorithm is proposed.Based on the existing impulse noise model and signal propagation model,the received signal strength（RSS）is calculated after the impulse noise is filtered by adaptive threshold pulse blanker.Then we get a rough estimate of the communication distance and time delay which will be used asthe initial time delay estimate of SETDE algorithm.Within a certain range of SNR,RSSI-SETDE algorithm will converge to the true time delay rapidly which is suitable for indoor ranging of fast moving targets.