# Earth-to-Earth Microwave Rain Attenuation Measurements: A Survey On the Recent Literature
## 5 Customized Experimental Setups
The effect of weather in electromagnetic wave propagation was studied over the Aegean Sea, Greece using data recorded from stations installed on several islands [73]. The main goal was to evaluate the attenuation level of microwave links based on local rainfall measurements. It was found that moderate precipitation caused a power loss of about 10-12 dBm at 2.4 GHz. Nevertheless, very little research has been carried out on wireless signal attenuation due to rainfall for frequencies lower than 5 GHz, mainly because the theoretical models consider it a negligible power loss for such low frequency. In this work, experiments took place in order to investigate this effect at the frequency of 1.8 GHz, used by the global system for mobile communications (GSM) [74]. Commercial mobile phones were used to report the received signal strength (RSS) from base stations (BSs) in dBm. The distance between BS and the mobile device was 400 m. Experimental measurements showed that the attenuation during the raining season was far greater than the theoretical expected one; furthermore, it is comparable to the theoretical attenuation caused by a frequency of 120 GHz. In addition, another potential factor affecting the attenuation was found to be the wind, causing fluctuations on the RSS level. In their next work [75], an alternative approach to rain attenuation was given that was focused on improved distance estimation through the study of sensed radio strength and precipitation. An in-depth view reveals that this work introduces a new enhanced received signal strength (RRS) distance estimator whereas it takes into account the precipitation, as well as the proposed path-loss model, includes rain attenuation for accomplishing an estimation based on an iterative form of [PERSON]'s method. Simulations and measurements verified the very good ability to estimate distance during precipitation with an adequate error reduction rate (85-90%) compared to that of the conventional scheme. For the purpose above, sensed precipitation data were taken into consideration (from a proposed estimator) from a local weather station (WS) or from the Central Weather Bureau (CWB). Specifically, rain rate acquirement was conducted with integration times of 30 min or more while the estimation error was at least 120 m when rain rate was equal to 20 mm/h. Additionally, the actually utilized band was that of the 1.8-GHz GSM mobile network. In their work [76], [PERSON] et al. had the goal of seeing only the effect of rain on signals on the W/V band that can be used for satellite communications. For this reason, in a small terrestrial path link and at a distance of 560 m in the New Mexico area, they measured signal attenuation due to rain at 84 GHz. The experimental setup included a disdrometer in the transmitter and receiver area for validation. The results were preliminary and were acquired in August 2016 for 27 days' time. Two scientists from Chosun University, Republic of Korea, analyzed rainfall and rain attenuation data for 3 years from 2013 to 2015 in the area [77]. The attenuation data came from 2 links with lengthsof 3.2 km and 0.1 km and operating frequencies of 38 and 75 GHz, respectively. The data were sampled every 10 s and averaged over one min. Data were obtained from National Radio Research Agency (RRA). An optical disdrometer OTT Parsivel was used to measure rainfall intensity and to validate rain attenuation. Attenuation over the same path link of 3.2 km was measured rain attenuation for 18 GHz operating frequency [78]. The same research team studied rain attenuation for a microwave link with 18 GHz and length 3.2 km [79]. The measurements took place in the period from 2013 to 2015 in South Korea. Both the rainfall data and the signal data were received by sampling every 10 s. The rain rate was measured using an OTT Parsivel laser optical placed near Receive Tower. Antennas are placed 30 m above the surface and they are protected by radome to prevent unwanted wetting antenna conditions.