# Earth-to-Earth Microwave Rain Attenuation Measurements: A Survey On the Recent Literature
## 6 Research Challenges
These types of links, for cellular network infrastructure, can be envisaged for an environmental sensor network (ESN). Particularly, the term \"sensor\" can be explicated as a radio link which binds a base station to the main network. For this kind of ESN, the main constraint is to produce algorithms for assessing the intensity of weather effects which compromise communication performance in the order of influence and i.e., rainfall and wind, humidity, fog, and snow. In [51], authors revealed the achievability of employing microwave communication links from a cellular infrastructure as ESNs intended for rainfall monitoring. In [91], a dataset of 2-yr time was retrieved by utilizing a C-band dual-polarization radar (C-Pol) (which is found near Darwin, Australia) is employed for extracting statistics of stratiform and convective precipitation into five large-scale regimes. The precise recovery of rain rates from attenuation measurements of commercial microwave links poses a demanding duty. For the purpose of acquiring reliable rain rate estimation, various matters need to be addressed such as baseline estimation and wet-antenna attenuation. The authors in [92], by utilizing the information from an experimental setup positioned in the area of Zurich, managed to calculate with unprecedented precision and temporal resolution the wet-antenna attenuation impacting a commercial microwave link. [PERSON] et al. underlined the combination of data from different sources, and a cognitive, high-resolution flash flood early warning system was also introduced. There were about 1800 rainfall stations in Kenya that do not support real-time monitoring. By integrating signal attenuation data from a telecommunication company with more than 3000 links and operating frequencies 7, 8, 15, 23 GHz and distances from a few km up to 80 km, vast amounts of data will be produced [93]. Precise measurements of precipitation are important for many applications, such as flash-flood warnings and water resource management. Nevertheless, the precision of the current tools is restricted due to several technical and practical factors. In [94], a survey of the current publications and works on this area of expertise has been presented. In [95], a method was introduced for the purpose of adjusting parameters of the power law locally, mostly in real-time, by using measurements from rain-gauges and existing CMN. In [96], a retrieval algorithm for rainfall mapping from microwave links in a cellular network as a substitute or supplement for continental-scale rainfall monitoring has been proposed. [PERSON] et al. negotiated the problem of creating rainfall maps through signal attenuation data [97]. A new retrieval algorithm was suggested for showing the abilities of microwave links to monitor rainfall inside urban areas. The area of research was the city of Nantes in France. The rain datasets came from 207 weather radar images. The microwave links of the area were 256 with path links varying from 0.3 to 16.8 km with operating frequencies of 18.23 and 38 GHz. In [98], the authors analyzed the impact of the quantizer along with the min/max operators on the signals levels measurements of commercial microwave links. They proved that the quantization process, in conjunction with the min/max operators, aggregates bias to potential important measurements. In addition to the previous, they suggested a way of calculating the bias and exhibited their results by using measurements from actual commercial microwave links. An affected link budget of microwave wireless communication has been properly studied for network design. The effects were originated from rainfall and other environmental phenomena. Nevertheless, the procedure has typically been conducted for every microwave-link separately. The attenuation in several microwave-links is currently being used in real-time for rainfall mapping of specific areas and particular algorithms have been designed for relating multiple microwave-links' attenuation to its corresponding rain-field.