applied sciences  
Modified REL-Based Piecewise Path Loss Modeling Approach for Shore-to-Ship Communication at 5.6 GHz  
[PERSON]\({}^{\copyright}\), [PERSON]\({}^{\copyright}\), [PERSON]\({}^{\copyright}\) and [PERSON]\({}^{\copyright}\)  
Footnote 10:  
efficiency of maritime activities, examining the marine environment as an electromagnetic wave propagation environment and correctly determining its effects are quite significant for reliable communication. Radio signals in the marine environment are affected by various factors such as sea state, salinity, water temperature, and differences in antenna heights, which change the propagation characteristics of the signals, such as reflection, diffraction, scattering, divergence, rain and atmospheric attenuations. Therefore, advanced propagation models that can adapt to environmental conditions are required to increase the reliability of shore-to-ship communication. Current research has focused on developing new propagation models to improve the performance of shore-to-ship and offshore communication systems. The need for broadband communication is of critical importance, especially in the exclusive economic zone (200 nautical miles), where states conduct their economic activities in the marine environment [1]. In addition to various activities such as oil and gas exploration, cargo and passenger transportation, and fish farms, the increase in autonomous systems and applications requiring remote control has increased the demand for reliable and efficient marine communication systems [2; 3]. In addition, an uninterrupted communication infrastructure is required for environmental applications such as monitoring, control of offshore wind energy farms, flood warning systems, and water quality assessments [4; 5; 6]. Therefore, the introduction of new-generation communication technologies, such as 5G, in the marine environment necessitates the development of marine propagation models to meet such communication needs [7]. In the existing literature, various empirical models such as free space, log-distance, dual-slope, and ray-based models (2-ray and 3-ray) have been developed to estimate path loss in terrestrial environments and have also been used in shore-to-ship communication. However, models such as the Round Earth Loss (REL) model, which considers more complex environmental factors and provides a higher accuracy, have also been proposed. However, each of these models may be inadequate for adapting to variable conditions in the marine environment. In recent years, the 5 GHz frequency band has become prominent in maritime communication studies. The support of this frequency band with international regulations, allowing higher transmission power and providing wider coverage, increases the effectiveness of maritime communication [8; 9]. In addition, organizations such as the European Telecommunications Standards Institute (ETSI) and the European Conference of Postal and Telecommunications Administrations (CEPT) recommend a frequency spectrum in the range of 5-8 GHz for maritime broadband radio communication [10]. In this context, to increase the accuracy and flexibility of path loss estimation in shore-to-ship communication, Modified REL and Proposed Piecewise models were developed for 5.6 GHz shore-to-ship communication in this study. In addition to the traditional REL model, the Modified REL model has additional parameters that consider the best receiver height (\(h_{rbest}\)) estimated according to the data pattern and the paths and gains of the direct and reflected waves. Therefore, it provides a better fit for the measured data in different sea scenarios. The Proposed Piecewise model, built on this model, divides the propagation environment into two different regions by determining the Fresnel distance, as in the double-slope model approach. The first region was modeled using a Modified REL, and the second region was modeled using the log-distance model.