In recent years wireless propagation channel research has paid considerable attention to dense multipath, which is an indispensable part of propagation channels and may significantly contribute to the received power in variety of environments and frequency bands. Mathematical representation of dense multipath is different from that of specular components (SCs) due to its distinct propagation mechanism and impact on system performance. Therefore, accurate understanding and modeling of dense multipath together with SCs are important for parametric channel estimation and for reliable simulation in wireless applications. This paper first presents a systematic survey of studies of dense multipath in terms of different representations, channel modeling approaches and estimation methods. Thereafter, a comprehensive review of the characteristics and impact of dense multipath on performance of communication, localization and sensing systems is provided. Finally, open research topics are discussed.

中文翻译：

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密集多径及其对无线系统影响的调查


近年来，无线传播信道研究对密集多径给予了相当多的关注，密集多径是传播信道中不可或缺的一部分，对各种环境和频段的接收功率都有显着影响。由于其独特的传播机制和对系统性能的影响，密集多径的数学表示与镜面反射分量（SC）的数学表示不同。因此，密集多径与 SC 的准确理解和建模对于无线应用中的参数信道估计和可靠仿真非常重要。本文首先对密集多径的不同表示、信道建模方法和估计方法的研究进行了系统的综述。此后，全面回顾了密集多径的特征以及对通信、定位和传感系统性能的影响。最后，讨论了开放的研究课题。