Passive Source Localization Using Time Differences of Arrival and Gain Ratios of Arrival

A source signal will be subject to different amounts of time-delay as well as attenuation when it reaches a number of spatially separated sensors. Both time-delay and attenuation are dependent on the distance between the source and the receivers. This paper performs a fundamental investigation of whether the gain ratios of arrival (GROAs), defined here as the ratio of the received signal amplitudes at the referenced sensor to the other sensors, can be utilized in conjunction with the time differences of arrival (TDOAs) to improve the source localization accuracy. We begin with a Gaussian random signal model and derive the Cramer-Rao lower bound (CRLB) of a source location estimate based on both GROAs and TDOAs. Our conclusion is that the improvement from GROAs increases when the factor c/omega_o increases, where c is the signal propagation speed and omega_o is the signal bandwidth. The paper proceeds to develop an algebraic closed-form solution for the source location using GROAs and TDOAs. The algebraic solution is proved theoretically to reach the CRLB accuracy under the Gaussian data model. Numerical simulations are included to support and corroborate the theoretical developments.     

无源到达时差定位技术分析

描述了无源定位技术的特性,分析了时差定位技术在二维平面和三维空间的基本原理,对时差定位精度进行了公式推导,对站址布局引起的时差定位误差进行了说明,概述了无源定位技术的发展趋势。     

到达时间差测量处理技术

短基线时差法测向体制原理简单,但需要现代化的时间间隔测量技术。本文给出一种到达时间差(DTOA)的测量处理方法,并给出实验结果。     

强干扰环境下水声时延估计技术研究

水声定位系统是现代深海作业必备的高精度水下定位装备,精确的时延估计是实现高精度水声定位的基础,但由于信号远距离传输以及强干扰的影响,水声定位系统时延估计精度较低.针对此问题该文提出一种基于子空间理论的宽带强干扰抑制方法,首先通过贝叶斯信息量准则估计子空间维度,然后推导了不同信号假设下的概率密度函数,求解未知参数的最大似然估计,构造广义似然比并通过最优匹配广义似然比检测法估计与期望信号最匹配的子空间,然后以此构造空间投影算子对接收数据进行线性投影,最终抑制干扰和噪声,提高时延估计精度.仿真结果表明该方法能够有效抑制干扰和噪声的影响,提高定位系统时延估计精度.     

对通信信号的时差估计技术

以循环相关理论为基础,讨论了利用循环互相关再相关法进行通信信号时差估计的算法原理,通过仿真验证了时差估计的效果。理论分析和仿真表明该算法具有优越的信号选择能力与干扰和噪声抑制能力;并指出了该方法的优缺点,阐明了该方法适合应用于对通信源的时差估计。     

电磁频谱监测时差定位初探

电磁频谱监测领域处理的信号特点是密集度高,采样率较低,时差定位技术应用难度大。针对此,分析仿真了相关峰插值与直接相关算法时差定位提取的性能,提出了工程上实用的电磁频谱监测时差定位的处理流程,更具有实用性。     

三维空间统计信道的空时参数AOA和TOA分析

针对在均匀散射体分布以及空间对称的3-D室内移动通信环境,细化了对于基站（BS,Base Station）以及移动台（MS,Mobile Station）端空间角度的研究。对在指向性天线覆盖下的室内微小区移动通信环境下,模型能估计多径衰落信道的重要空时信道参数,如波达信号在水平面以及竖直平面上的信号到达角度（AOA,Angle of Arrival）以及到达时间（TOA,Time of Arrival）。数值仿真结果与2一D多径衰落信道对比表明本模型的信道参数估计结果符合理论和经验,扩展了3一D空间统计信道模型的研究和应用。     

穿过电离层电子密度不均匀体的脉冲平均到达时间

本文利用前向多重散射理论的新进展，推导了穿过电离层电子密度不均匀体脉冲平均到达时间的理论计算公式，其中包括背景介质折射效应的贡献、色散效应的贡献、电离层电子密度不均匀体的散射效应的贡献和色散效应的贡献，在水平分层背景电离层和高频近似的情况下，给出了背景电离层折射效应、一阶色散效应、电子密度不均匀体的散射效应和一阶色散效应对对称脉冲平均到达时间影响的计算公式。针对特定的电离层情况，分别计算了上述几种     

一种新颖的时延与到达角联合估计算法

本文提出了一种新颖,有效的时延与到达角联合估计算法.算法在频域空间建立了关于到达角向量和时延向量的可分维数据结构.利用PRO-ESPRIT算法获得了到达角的精确估计,同时借助子阵矩阵束的广义特征向量实现了不同时延向量的分离快速估计,并提出了基于ESPRIT的时延快速估计方法.仿真实验显示了本文算法计算量小,性能优良.     

Efficient Spectrum Allocation and Time of Arrival Based Localization in Cognitive Networks

Position of the primary user is significant to the transmission among secondary users in cognitive networks (CN). In this paper, orthogonal frequency division multiplexing (OFDM)-based spectrum allocation and time of arrival-based localization are proposed for the devised CN. Crame?CRao lower bound for range estimation is theoretically derived in terms of the proposed spectrum allocation in CN, compared with that of the nonoverlapped allocation in CN and OFDM-based static spectrum allocation in noncognitive networks (NCN). The 2D localization accuracy is investigated based on horizontal dilution of precision (HDOP). The theoretical minimum HDOP is explored and the corresponding network topology to attain the minimum HDOP is provided. Theoretical analysis and simulation results demonstrate that the proposed spectrum allocation in CN exhibits a much better ranging and localization accuracy, and a better data transmission rate than the nonoverlapped spectrum allocation in CN, no matter the designed spectrum with nonoverlapped allocation is a sinc function or a rectangle. Also, the proposed spectrum allocation in CN is demonstrated to have a better ranging and localization accuracy than OFDM-based static spectrum allocation in NCN.     

Passive Orbit Measurement of Geosynchronous Satellite Based on Four-station's Time Difference of Arrival

基于卫星通信信号的多站时差测轨是一种重要的新型无源测轨方法,分析其定轨精度对系统应用具有重要意义.介绍了四站时差测轨原理与系统组成,提出了基于四站时差测量数据的自校准统计定轨策略,采用计算机仿真了同步轨道卫星的统计定轨精度.仿真结果表明:当无系统误差时,24h观测数据统计定轨位置误差约为11m,预报1周位置误差约100 m;当存在系统误差时,可用自校准方法同步估计系统误差,系统误差估计精度约为4m,位置误差约为120 m,预报1周的位置误差约为200 m.     

Spread Spectrum Medium Access Protocol with Collision Avoidance Using Controlled Time of Arrival

The spread spectrum technique, the collision avoidance multiple access protocols and the controlled time of arrival scheme are combined to form a new set of medium access protocols for wireless networks. The Request-to-Send and Clear-to-Send message dialogue helps a transmitter detect whether an intended receiver is busy and whether any collision has occurred; thus speeding up the retransmission. The spreading code assignment avoids the disruption of any ongoing transmission by an intruder. Finally, the packets are sent under controlled time of arrival to further increase the channel throughput. Simulation results confirm that a higher channel throughput is achieved by the new protocols even in a dense network.     

一种基于谱相关特性的时差估计方法

在现代无线电侦查所处的环境中,信号数量多,且复杂密集,通常会有多个信号同时进入接收机带宽范围。进入接收机的很多信号是循环平稳信号,循环平稳信号的谱相关特性具有选择信号的能力。基于循环平稳信号的谱相关特性,研究了一种可以对多信号进行时差估计的方法。理论分析和仿真验证表明,在多信号环境下,该方法可以准确估计各个循环平稳信号...     

移动通信

诺基亚2680 slide;诺基亚7070Prism;Plantronics 925系列。     

环球搜新

多普达新品牌vivie登场;惠普MVC计划助力中国网通构建宽带网络;联想退出数码相机市场;英特尔2008年推自有品牌主板。