Localization of an object by signals of opportunity may not have the transmitter position and the synchronization with the transmitter. Additionally, a receiver may not be able to resolve the separate time delays of the line of sight signal from the transmitter and the back-scattered signal by the object, and it is only able to obtain the difference between the two. This paper investigates the use of such differential time delays (DTDs), one from each receiver by itself without the need of synchronization with the others, for positioning the object; and shows that localization is possible in absence of transmitter position. The performance is not necessarily worse than, and indeed can be better than, the TDOA approach that can operate without the transmitter position but dictates receiver synchronization. We then propose the use of both DTDs and TDOAs for improving the positioning accuracy and analyze the expected performance. Algebraic solutions are next derived for localization by DTDs, and by DTDs together with TDOAs. Theoretical study illustrates that the solutions attain the Cramer-Rao Lower Bound accuracy under the Gaussian noise model. A refinement step is also developed to extend the noise level for matching with the CRLB performance.

中文翻译：

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在没有发射机位置的情况下通过机会信号进行定位


通过机会信号对对象的定位可能没有发射器位置以及与发射器的同步。此外，接收器可能无法解析来自发射器的视线信号和物体的反向散射信号的单独时间延迟，并且只能获得两者之间的差值。本文研究了使用这种差分时间延迟（DTD）来定位物体，每个接收器单独使用一个差分时间延迟（DTD），无需与其他接收器同步；并表明在没有发射器位置的情况下定位是可能的。其性能不一定比 TDOA 方法差，而且实际上可以比 TDOA 方法更好，TDOA 方法可以在没有发射器位置的情况下运行，但需要接收器同步。然后，我们建议使用 DTD 和 TDOA 来提高定位精度并分析预期性能。接下来通过 DTD 以及通过 DTD 与 TDOA 一起导出代数解以进行本地化。理论研究表明，该解在高斯噪声模型下达到了 Cramer-Rao 下界精度。还开发了一个细化步骤来扩展噪声水平，以与 CRLB 性能相匹配。