# Earth-to-Earth Microwave Rain Attenuation Measurements: A Survey On the Recent Literature
## 5 Customized Experimental Setups
Comparison with ITU-R P.530-16, [PERSON], Silva Mello, and Abdulrahman models with the proposed prediction model was also discussed. Experimental results were observed to be undervalued due to the ITU-R P.530-16 model. Customized measurement equipment with 10\({}^{-4}\) dB power resolution and a signal-to-noise (SNR) ratio of 145 dB, with sampled values of 0.2 min, was introduced by [PERSON] et al. [80]. Validation of data was accomplished through the conventional 0.2 mm per tip rain-gauge. The experimental setup included transmitter and receiver at a distance of about 20 m between them so that the rainfall to be uniform. The antennas were located inside two adjacent buildings in order not to be present the wet antenna attenuation and wind jitter errors. Rainfall amount from 0.2 to 0.8 mm was measured over one year from 2015 to 2016. The measurements took place within the University of Ioannina campus near the town of Ioannina. Furthermore, the same research group from Greece presented a rain attenuation model in the lowest region of the microwave S-band validating signal and rainfall data from one-year measurements [25]. [PERSON] et al. made an assessment of the rainfall based on received signal level features from an LTE/4G mobile terminal [81]. For their measurements, they used the Mobile terminal and the G-Mon application, which gave a report of parameters related to received signal strength, connection type, etc. The data was recorded by sampling for 1 min. The datasheet included data obtained for more than 112 h in the area of Catania, Sicily, Italy. The receiver (mobile terminal) had been placed at a distance of 200 m from the base station. For the correlation of the data, a tipping bucket rain gauge was used at the same point as the mobile terminal. They also presented a classification method based on a probabilistic neural network so that there is a separation into four possible rainfall conditions no-rain, weak, moderate, and heavy rain. In Malaysia, two research teams implemented a 5G radio link with a length of 1.3 km and an operating frequency of 26 GHz [82]. The link was set up between WCC, University Technology Malaysia, Johor Bahru and Skudai. The radio-based system was based on an Ericson mini link CN 500. For rainfall, a tipping bucket was used with 0.5 mm sensitivity while the data were collected in the logger every minute. The measured attenuation over the path link exhibited a maximum value of 34 dB which this fact can significantly affect communication. Exploring the feasibility of creating a wireless disaster alarm system, two microwave links were employed measuring the degradation of received signal level due to rainfall. The links were operated at frequencies of 5 GHz and 26 GHz [83]. The microwave attenuation was correlated with rain rate measurements by tipping bucket gauges. The used model for attenuation due to rain presence is \(\text{A}~{}=~{}aR^{b}\), where \(R\) is the rain rate in mm/h, A is the attenuation in dB/km and \(\alpha\), \(b\) are constants depending on frequency. The constant parameters were found to be the following; for the 5 GHz link \(\alpha\) = 1.3479, \(b\) = 0.2045. For the 26 GHz, link tow differences were found between master and slave terminals mainly caused by different rain gauge resolutions. For the master terminal \(\alpha\) = 1.6908, \(b\) = 0.5348, using a 15-min gauge resolution, same as for the 5 GHz link, while for the slave terminal \(\alpha\) = 2.1139, \(b\) = \(-\)0.8724, using event-driven tipping bucket. The 26 GHz link was more susceptible to attenuation due to rain compared to the 5 GHz one. A custom experimental setup operating at 22.84 GHz and 77.52 GHz K and E band, respectively have been designed by [PERSON] et al. [84]. Measurements took place from January to December 2018 at Durham, UK. The path link between the Tx and the Rx antenna was 35 m. The rain attenuation was related to rainfall events by a PSW100 dichrometer. The PSW100 rain data were logged every minute, while channel data were recorded with a sampling rate of 1 s per min.