## 5 Reviewed Papers on Empirical-Based Path Loss Models
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & **Freq.** & \multirow{2}{*}{**Model**} & \multirow{2}{*}{**Scenario**} & \multirow{2}{*}{**Environment**} & \multicolumn{2}{c}{**Area of**} & \multirow{2}{*}{**Important Results**} & \multirow{2}{*}{**Drawback**} \\  & **(GHz)** & & & & & & & With a lower RMSE & The magnetic optimization \\  & & & & & With the dataset & value, the proposed & algorithm that was & algorithm that was \\
[42] & 1.8 & FSPL and & & & gathered from drive & augmented model & used has deficiencies \\  & & FSPL and & & & tests, the proposed & outperformed and & in handling \\  & & COST-231 & LOS & Urban & model was tuned & was more & non-linearity and \\  & & & & & using the magnetic & representational of & may suffer from \\  & & & & & optimization & the data than its & convergence issues \\  & & & & & algorithm (MOA). & traditional & to provide an \\  & & & & & & counterparts. & accurate model. \\ \hline \multirow{6}{*}{[72]} & \multirow{6}{*}{2.5} & \multirow{6}{*}{2.5} & \multirow{6}{*}{LOS} & Five different & The COST-231 Hata & The COST-231 Hata & The COST-231 Hata & model needs to be \\  & & & & & were tested with & model proved to be & fine-tuned to suit the \\ \cline{1-1}  & & & & actual data & more suitable than & special scenario of \\ \cline{1-1}  & & and & & measurements to & the other chosen & the urban \\ \cline{1-1}  & & & & find the most & & models, with a & environment that \\ \cline{1-1}  & & & & performed model to & minimal RMSE of & comprises old and \\ \cline{1-1}  & & & & predict path loss. & 5.27 dB. & modern buildings. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._this case, instead of one PLE as in the case of the log-distance model, the proposed model contains multiple exponents, and each stands for a parameterized environmental factor (PEF). To verify the proposed model, parameters via measurement were extracted, and its performance was compared with the log-distance model. The results demonstrate that the proposed model is a better-performed model. Meanwhile, the proposed model needs to be tested on other frequency bands to accurately determine its stability. The authors in [71] suggested a novel large-scale propagation model for 5G wireless communication systems, which is expected to be reliable for indoor environments. Simulations were run for all polarizations at two distinct scenarios per meter over 47 m to compare and validate the proposed model with current models. The findings demonstrated that the straightforward ZMS model, which only included one parameter, allowed for a more accurate prediction of path loss over a distance. To get a representative model, however, an extensive measuring effort across comparable structures will be necessary. The authors in [42] optimized the conventional COST 231 Hata model in the city of Limbe in Cameroon using an optimization algorithm, such as the magnetic optimization algorithm (MOA), to predict path loss within the mid-band of 2 GHz. Even though reasonable prediction results were achieved with the proposed model, the magnetic optimization algorithm that was used has deficiencies in handling non-linearity and may suffer from convergence issues to provide an accurate model. In another paper presented by [72], five different empirical models--the FSPL, GUI model, Ericsson model, Okumura model, and COST-231 Hata model--were compared with empirical data measurements to find the best suitable model to predict path loss in the urban environment of Cologne, Germany, at 2.5 GHz. The analytical results showed that the COST-231 Hata model was the most suitable, with a minimum RMSE of 5.27 dB. Meanwhile, the COST-231 Hata model needs to be fine-tuned to suit the special scenario of the urban environment that comprises old and modern buildings. In this case, novel indicators from the measurement campaign will be used to tune the model.