Regression-Based Modeling and Contour Mapping of Radio Refractivity in Nigeria For Improved Link Budget Design

Abstract: The performance of radio signals propagating through the lower atmospheric layers is influenced by their refractive conditions. To ensure that the effects of propagation do not compromise the strength of signals transmitted, link budgets must be carefully designed. The International Telecommunication Union (ITU) model is the globally accepted standard for estimating radio refractivity. However, due to climate variability, researchers have reported overestimations and underestimations of radio refractivity by the ITU model in tropical climates. In response, this study introduces a novel modeling approach by developing a new empirical model for estimating radio refractivity and generating contour maps to enhance existing link budgets in Nigeria. Ten years of atmospheric parameter data from twelve locations across different climatic regions of Nigeria were obtained from the Center for Atmospheric Research (CAR), Anyigba, Nigeria. Using these data, a new refractivity model was developed and statistically validated with R-squared and Root Mean Squared Error (RMSE) metrics. Subsequently, refractivity contour maps for Nigeria were created using Surfer 16 software. The analysis revealed that the proposed model achieved R-squared and RMSE values of 0.99 and 0.27, respectively. Additionally, annual refractivity contour maps indicated a progressive increase in refractivity values from the northern (dry) regions of Nigeria to the southern (coastal) region. The study also demonstrated that refractivity values vary across climatic regions. Thus, this work can be employed for the quick and precise link budgets estimation in the design and planning of radio links in Nigeria and other regions with comparable climatic conditions.