多天线时变信道频偏的估计下界

针对多天线信道频偏参数的随机时变特点,建立参数化的观测模型,根据时变参数估计的克拉美-罗下界求取原理,在非线性的观测模型和序贯的观测值下,利用参数真值推导频偏估计的克拉美-罗下界。由于特征参数的真值不可知,因此将观测模型在估计值处进行二阶泰勒级数展开,通过参数估计值获得频偏参数估计的近似下界。仿真结果表明,基于参数真值和估计值的频偏估计下界具有渐近收敛性,且随信噪比和观测值个数的增加均能达到稳态。     

Efficient closed-form solution for target localization using TDOA measurements in the presence of sensor position errors

An efficient solution for locating a target was proposed, which by using time difference of arrival (TDOA) measurements in the presence of random sensor position errors to increase the accuracy of estimation. The cause of position estimation errors in two-stage weighted least squares (TSWLS) method is analyzed to develop a simple and effective method for improving the localization performance. Specifically, the reference sensor is selected again and the coordinate system is rotated according to preliminary estimated target position by using TSWLS method, and the final position estimation of the target is obtained by using weighted least squares (WLS). The proposed approach exhibits a closed-form and is as efficient as TSWLS method. Simulation results show that the proposed approach yields low estimation bias and improved robustness with increasing sensor position errors and thus can easily achieve the Cramer-Rao lower bound (CRLB) easily and effectively improve the localization accuracy.     

On the use of calibration sensors in source localization using TDOA and FDOA measurements

The accuracy of a source location estimate is very sensitive to the presence of the random noise in the known sensor positions. This paper investigates the use of calibration sensors, each of which is capable of broadcasting calibration signals to other sensors as well as receiving the signals from the source and other calibration sensors, to reduce the loss in the source localization accuracy due to uncertainties in sensor positions. We begin the study with deriving the Cramer–Rao lower bound (CRLB) for source localization using time difference of arrival (TDOA) and frequency difference of arrival (FDOA) measurements when a single calibration sensor is available. The obtained CRLB result is then extended to the more general case with multiple calibration sensors. The performance improvement due to the use of calibration sensors is established analytically. We then propose a closed-form algorithm that can explore efficiently the calibration sensors to improve the source localization accuracy when the sensor positions are subject to random errors. We prove analytically that the newly developed localization method attains the CRLB accuracy under some mild approximations. Simulations verify the theoretical developments.     

基于多星时差定位精度分析

利用矩阵理论和统计信号处理理论,推导了由于时差、卫星自定位和卫星速度等测量误差产生定位误差几何稀度(GDOP)公式。并以四星为例,在地固坐标系模型下给出了仿真结果。仿真表明:地球约束能显著提升定位精度;卫星自定位误差为10m时对卫星的定位精度影响较大。     

双频雷达动目标近场定位算法

利用双频雷达对运动目标进行定位现已受到广泛关注。虽然已有文献对双频雷达进行了一些研究,但这些方法都是基于远场假设的。因此,提出了一种简单的基于菲涅耳模型的利用单站双频雷达进行近场定位的新方法。有别于现有方法需要联合搜索或者需要复杂的矩阵运算,该方法仅使用简单的代数运算就能提供闭式解,可直接应用于低成本的嵌入式设备。此外,推导了单站双频雷达定位问题的克拉美罗下界（CRLB）,为性能评估提供了基准。仿真结果验证了该方法的有效性。     

地形特征对粒子滤波导航算法精度影响分析

地形导航是利用飞行器下方地形估计飞行器空间位置的导航方法。由于地形是强非线性模型,因此地形导航可以看作非线性状态估计问题,地形特征直接影响导航精度。在讨论粒子滤波导航算法基础上,重点研究了地形特征对后验概率密度和Cramer-Rao下界的影响,得出了地形梯度和相似度是影响粒子滤波导航算法精度的根本原因,为飞行区域选择、飞行路径规划提供了依据,具有较强的实用性。     

Improved taylor-series location algorithm for cooperation networks

This article presents an iterative algorithm for estimating the location of the destination mobile station (DS) when some extra mobile stations around the DS are involved in and assist the base stations to complete the localization process. The proposed method is based on the taylor-series (TS) method and jointly estimates both the DS and the extra mobile stations, named reference mobile station (RS) in this article, positions simultaneously. Moreover, the time-differential-of-arrival (TDOA) measurements between DS and pairs of RSs are obtained by ultra-wide-band (UWB) signal, which is adept in accurate ranging application. According to the theoretic analysis, the Cramér-Rao lower bound (CRLB) of the modified TS algorithm reduces significantly. The actual performance, under a given simulation scenario, is enhanced by 25% at best.     

相位噪声对时差估计的影响分析

在到达时间差(TDOA)测量中,两异地接收站所配备的本振都会存在相位噪声,该相位噪声会影响时差测量的性能。该文分析了相位噪声对经典的互相关法时差估计无偏性的影响,同时推导了仅考虑相位噪声时TDOA估计精度的克拉美罗下限(CRLB)。并进一步得到了相位噪声与加性噪声都存在时的CRLB及其相对于加性噪声环境下的CRLB退化系数。仿真结果验证了理论分析的结果。     

突发GMSK混和信号混合位置估计迭代算法

针对GMSK混合信号的混合位置估计问题,提出了一种基于参数估计与混合位置估计的迭代算法。混合信号混合部位和未混合部位在幅度和频率上存在明显差异,通过混合部位信号过零点和极值点得到混合的信号和幅度估计后,可以对采样点是否混合进行判断,同时混合起点对应着相对时延,当混合信号的相对时延较大时,利用未混合部位信号来进行迭代时,其估计精度更高。对混合起点估计的克拉美罗界进行了推导,仿真表明,本文算法估计精度高,所需的数据量小,适用于突发通信,且对参数变化不敏感,具有较强的鲁棒性,在高信噪比下混合位置估计精度接近克拉美罗界。     

不完全量测下基于事件触发机制的面目标跟踪系统CRLB

面目标跟踪系统状态估计问题中,附加的强非线性面目标扩展测量会增加系统的通信量和估计中心的计算量.为此,基于工程应用,提出一种不完全量测下的事件触发机制来控制面目标测量传输.从理论上推导了事件触发机制下面目标跟踪系统的理想（枚举）克拉美罗下界（Cramer-Rao lower bound,CRLB）和统计意义下的CRLB,该统计意义CRLB为理想CRLB的下界,计算复杂度远小于理想CRLB,便于工程应用.典型测试航路下的仿真结果表明：不完全量测下,面目标跟踪系统CRLB明显小于传统质点目标跟踪系统CRLB;同时,利用所提事件触发机制,可在大幅减少面目标跟踪系统通信量的同时保证系统的最优估计性能.