## 1 Introduction
In addition, they were selected because ITU-R has supported their use as references for new approaches over the UHF channel [32]. Lastly, all independent parameters in the models are available in the data collected in this study, and the different environment definitions are equally compliant. However, it is difficult to determine which of the improved versions would be most suitable for terrains and environments or climates different from the original environments in which they were formulated. Table 1 presents some closely related studies (cited in this work) indicating the methods, locations, and key findings. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Reference** & **Nature of Work/Location** & **Main Finding(s)/Limitations/Strengths** \\ \hline
[6] & Drive test protocols (DTPs) deployed for data & \\  & collection in three environments in Kwara State, & Hata and Davidson models recommended for \\  & Nigeria. Empirical path loss model (EPLM) & prediction, limited to analog channels, \\  & performances investigated for VHF/UHF channel. & no optimization. \\ \hline
[7] & DTPs deployed for data collection over analog & \\  & UHF channels in Ondo State, Nigeria. EPLMs & Davidson model recommended, no optimization, \\  & were tested. & limited to analog channel. \\ \hline
[9] & Measurements by DTPs over GSM 900 MHz in & \\  & urban, suburban, and rural areas of, Dar es Salaam, & ECC-33 recommended, especially in suburban \\  & Tanzania. EPLMs were tested. & areas, no optimization. \\ \hline
[12] & Propagation measurements by DTPs over GSM 4G & Okumura–Hata performed best and \\  & in urban and suburban areas of Lagos, Nigeria. & was optimized. \\ \hline
[14] & Propagation measurement by DTPs over 900 MHz & \\  & in West of Amman, Jordan. Terrain roughness & Modified Hata model proposed over microcell. \\  & incorporated in Hata model. & \\ \hline
[18] & Propagation measurements of three FM signals in & Proposed new models for FM path loss, limited \\  & office buildings scenarios in Philippines. & to FM channels. \\ \hline
[24] & DTPs employed for data collection over DTV in & \\  & Kano City, Nigeria. Okumura model used for path & Modified Okumura model proposed, limited to a \\  & loss assessment. & model, no optimization. \\ \hline
[27] & DTPs employed for data collection over DTV in & \\  & Katsina City, Nigeria. Performance evaluation of & COST-231 performed best and is recommended \\  & seven EPLMs carried out. & for use, no optimization. \\ \hline
[28] & Studied seasonal characteristics of rainfall rate and & \\  & rain-induced attenuation on earth–satellite link & ITU-R 618-13 (2017) was modified for use. \\  & in Akure. & \\ \hline
[29] & Investigated the channel fading path loss over an & \\  & air-to-ground link at 700 m. & Shadow fading has a high dependence on UAV. \\ \hline
[30] & A 3-D radio environment map based on sparse & Results had higher accuracy under the low \\  & Bayesian learning was developed. & sampling rate. \\ \hline
[31] & Propagation measurement by DTPs over GSM 4G & \\  & in urban and suburban areas of Ibadan, Nigeria. & COST-231 performed best and was optimized. \\  & Three EPLMs were tested. & \\ \hline
[33] & Field measurements were conducted to determine & \\  & path loss over WiMAX, in Cyberjaya, Malaysia. & COST-231 performed best and was optimized for \\  & Performance evaluation of three EPLMs & use over 2360–2390 MHz band, in the urban and \\  & carried out. & suburban environments. \\ \hline
[34] & Channel parameter estimation of mmWave MIMO & Noise weighting was introduced in their \\  & system was carried out in urban traffic scene. & proposed method, and the simulated results \\  & system was carried out in urban traffic scene. & showed validity of the method in \\  & frequency-selective mmWave MIMO channel. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Closely related studies indicating the methods, locations, and key findings.