# Earth-to-Earth Microwave Rain Attenuation Measurements: A Survey On the Recent Literature
## 1 Introduction
The current paper can be beneficial, especially for new researchers in the field of rain rate determination via remote sensing. By reading this article, the reader can fully understand the recent progress made towards this direction, the main challenges stumbled upon, how they were partially overcome, and which challenges remain to be addressed. Having to investigate each published paper separately can be tedious because of its massive amount of data. Getting a general idea of the work done in this field can also be time-consuming for the same reason. The current survey makes possible for readers to find papers easier related to their interests. In other words, publications that match someone's interests can be easily found through this paper so that they can be accessed for in-depth reading. Researchers can easily find similar approaches for their related ongoing works (measuring techniques used, path length, frequency, location, etc.). At the same time, they are able to determine which approach, or combination of approaches, best suits their needs, without having to go through the literature extensively. Given the fact that this paper mentions and analyzes a considerable amount of information from recent literature relevant to earth-to-earth microwave rain attenuation, and thus with the need to avoid being chaotic, the organization of the paper is given below along with the explanation of its general structure. Consequently, this survey is organized with the following structure: In Section 2, the methodology and literature search is described. Then, in Section 3, the theoretical and experimental framework of the signal attenuation due to rainfall is presented. Section 4 classifies rainfall measurements works related to backhaul cellular infrastructure. Section 5 classifies customized experimental setups. Research challenges are described in Section 6. Finally, conclusions are reported in Section 7. The aforementioned paper structure is reported in this way in order to form a flow path which can lead to better reading the significant conclusions. Specifically, Section 2 gives the methodology while it informs the reader of the kind of structure that this paper exhibits based on scientific facts while Section 3 analyzes the theory in order the reader to obtain the most basic knowledges for properly interpreting the provided experimental framework. Then, in Section 3, as the readers can now understand basic results on this area of expertise, a classification is imminent in order to lead them properly through the reading process, while Section 6 comes to complete the classification by adding the experimental part. Then, by having acquired the basic knowledges from the classification, research challenges must be mentioned in order to show the current restrictions in the current development and what someone should expect and work towards in the near future. Then, the final section follows, which includes discussion and conclusions for finalizing this literature review. Especially this final section of the paper exhibits generic recommendations because in the condition that further details would had been given in conclusion, then these would had been taken from all the related works which exhibited a diversity in their findings and that condition would had been non-functional for the reading process. Consequently, if the readers want to have a quick glance at the last decade of the the thematic area of this paper, they should quickly read the remaining paper or at least Section 6 which provides limitation issues apart from useful research challenges.