# A Review on Rainfall Measurement Based on Commercial Microwave Links in Wireless Cellular Networks
## 3 Development of Rainfall Measurement Based on CML
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Authors (Year)** & **Country (GHz)** & **Frequency (GHz)** & **Link Number** & **Length (km)** & **Temporal Resolution** & **Quantization Level (dB)** & **Remarks** \\ \hline [PERSON] et al. (2006) & Israel & — & — & — & 15 min & — & The correlation between rainfall intensity measured by CML and RG is 0.86 for a 15 min interval and 0.9 for an hourly interval. \\ \hline [PERSON] et al. (2007) & The Netherlands & 38 & 2 & 7.75, 6.72 & 15 min & 1 & Eight rainfall events are evaluated, and the results are consistent with the rainfall retrieved from RGs and C-band radar. \\ \hline [PERSON] et al. (2010) & France & 26, 19 & 4 & 3.7, 3.7, 7.1, 24 & 30 s, 6 s & 1 & A week and dry weather classification method is proposed, which can identify 92\% of all rainy periods and 93\% of the total rain amount. \\ \hline [PERSON] et al. (2012) & Germany & 15, 18, 7, 23 & 5 & \begin{tabular}{} \end{tabular} & 5 & \begin{tabular}{} \end{tabular} & \begin{tabular}{} \end{tabular} & \begin{tabular}{} \end{tabular} & \
\begin{tabular}{} \end{tabular} &
\begin{tabular}{} \end{tabular} \\ \hline [PERSON] et al. (2013) & Switzerland & 23, 38, 58 & 14 & 0.3–8.4 & 5 min & 0.1 or 1 & RGs, weather radar and CMLs are combined to estimate the intensity and temporal distribution of rainfall more accurately. \\ \hline [PERSON] et al. (2013) & Czech Republic & 38 & 14 & — & — & — & CML networks can better capture the spatio-temporal rainfall dynamics, especially in heavy rain, and thus improve pipe flow prediction. \\ \hline [PERSON] et al. (2014) & Burkina Faso & 7 & 1 & 29 & 1s & 1 & 95\% of the rainy days are detected by CML measurement, and the correlation with the RGs data series is 0.8 \\ \hline [PERSON] et al. (2016) & Italy & 25 & 3 & average of 6 & — & — & Tomographic technique was applied to reconstruct 2-D fields of rainfall accumulation, and the link density and topology affect the accuracy of the reconstruction algorithm. \\ \hline [PERSON] et al. (2018) & Brazil & above 15 & 145 & shorter than 20 & — & 0.1 & As compared to RGs, CML-based measurement can better capture the city-average rainfall dynamics. \\ \hline [PERSON] et al. (2018) & Pakistan & 38 & 35 & 0.5–2.5 & 15 min & — & The correlation coefficient value between rainfall intensity measured by CMLs and RGs is as high as 0.97. \\ \hline [PERSON] et al. (2020) & Sweden & 14–39 & 17 & 1.5–7 & 10 s & — & Using long short-term memory (LSTM) to learn from previous attenuation values is sufficient to generate accurate attenuation predictions. \\ \hline [PERSON] et al. (2021) & China & 15–23 & 8 & 0.55–1.08 & 1 min & 0.1 & The correlation coefficient values between the rain rate measured by CMLs and RGs are higher than 0.77, and the highest coefficient is over 0.9. \\ \hline [PERSON] et al. (2021) & Australia & 10–40 & 144 & 0.2–57 & 15 min & 0.1 & Using two types of datasets collected by different sampling strategies (maximum/minimum RSL and average RSL) to retrieve rainfall, the results show that the maximum/minimum RSL data are better than average in terms of the statistics, i.e., root mean square error (RMSE), bias, and coefficient of variation (CV). \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Countries that have used CML to measure rainfall.