## 5 Conclusions  
This study investigated the degree of reliability (performance evaluation) of four widely used empirical path loss models (the Hata, COST-231, ECC-33 and Ericsson models) on UHF channels, specifically over the digital UHF channels in Ikorodu, Lagos and Akure, Southwestern Nigeria. Data were obtained from rigorous in situ measurements of the received power, transmitter-receiver distance, and other necessary transmission parameters of the digital terrestrial UHF TV base stations studied. For the Ikorodu DTBS, the overall mean value of the measured path loss for the two routes and seasons was 110.42 dB, while the predicted values were 121.90, 123.55, 158.42, and 291.01 dB for the Hata, COST-231, Ericsson, and ECC-33 models, respectively. The Hata model performed the best, with the smallest RMSE of 10.812. These findings show that Hata is the preferred prediction model for use in the Ikorodu environment. In addition, findings in the suburban city of Akure  
Figure 8: Variation in measured path loss using the untuned Hata and optimized Hata models in the Ikorodu environment. Figure 9: Variation in the measured path loss using the untuned and optimized COST-231 models in the Akure environment. reveal that the overall mean value of the MPL was 123.157 dB, while the PPLMs were 121.922, 130.179, 198.979, and 313.494 dB for the COST-231, Hata, Ericsson, and ECC-33 models, respectively. In the study area, the COST-231 model had the best performance, with the smallest RMSE of 9.877. The Hata model presented the next best performance, with an RMSE of 11.799. These findings show that both the COST-231 and Hata models are suitable to predict path loss over digital terrestrial UHF signals in the suburban city of Akure. This is based on the fact that their RMSE values were comfortably within the 7-15 dB range, which is acceptable for suburban cities [8; 38]. However, COST-231 is preferred for use in the study area. The differences in the performances of Hata and COST-231 in the two environments could be attributed to the terrain factors of the individual environments. Optimization of the preferred models was carried out using logarithmic regression analysis to increase their reliability. Newly optimized Hata and COST-231 models were developed. The Hata model showed an improved RMSE of 5.895 compared to 10.810 dB of the untuned model, while the COST-231 model showed an RMSE of 7.815 compared to the value of 9.877 dB of the untuned model. The difference in the performances of the models in the two environments could be attributed to their terrain and atmospheric factors. The optimized models have higher degrees of reliability and can provide a valuable approach to wireless communication planning in tropical urban and suburban environments, with the aim of enhancing quality of transmission and reception (QoTnR) over UHF channels in Nigeria and similar environments in Africa. The novelty of these models underscores their ability to enhance signal's performance. For example, no matter how small a signal's gain (1, 2, 3 dB) may look practically, it can be highly significant in wireless communications and prevent a signal from crossing the sensitivity value(s). The optimized model in Figure 8 shows an improved RMSE from 10.810 to 5.895 dB, bringing it into the acceptable range for urban areas. In Figure 9, the optimized model shows an improved RMSE from 9.877 to 7.815 dB, which is still suitable and well within the acceptable range. These models are strongly recommended for path loss prediction in these environments. The Ericsson and ECC-33 models are not fit for use in these environments based on their inaccurate predictions and mostly out-of-range RMSE values obtained in this study. Other general findings include that measured path loss values were greater during the wet season months than in the dry season months, and they increased with the Tx-Rx distance. The path loss profile depicts the influence of terrain roughness, while the PPLM profile shows a smooth exponential rise with distance.