# A Clutter Loss Model for Satellite Communication Systems
## 1 Introduction  
Access to the mid-band spectrum (above 6 GHz) is of primary importance to boost the capacity of lower-band 5G systems. A recent study [1] performed by Coleago Con-sulting on mid-range frequency usage for 5G mobile service indicates that an additional band of 1.2 GHz is required to meet the International Mobile Telecommunications-2020 (IMT-2020) user-experienced data rates of 100 Mbit/s in downlink and 50 Mbit/s in uplink. There is a significant benefit when the 5.925-7.125 GHz band is accessible by IMT in support of 5G-NR (New Radio) and its evolution [1]. At the next World Radio Conference 2023 meeting (WRC-23), agenda item 1.2 will discuss the harmonization of the 6 GHz band in accordance with Resolution 245 (WRC-19) [2]. In fact, the harmonization of the IMT frequency and bands on a regional/global scale will provide economic benefits. In this scenario, the coexistence of IMT services above 6 GHz with GEO (geostationary Earth orbit) satellites with a C-band payload may represent a limiting factor for the allocation of the mid-band spectrum to the former. Fixed satellite services currently use the 6 GHz band to upload contents via gateways. In mid-2020, the Federal Communications Commission (FCC) resolved to allocate the mid-band to unlicensed users to maximize its usage while protecting incumbents from harmful interference [3]. The validation of the system coexistence is discussed at the global level among the ITU-R (Radiocommunication Sector of International Telecommunication Union) working groups. These technical teams are working towards the provision of models and parameters to be employed in the definition of coexistence simulations. The Working Party (WP) 5D, responsible for carrying out studies under WRC-23 agenda item 1.2, soliected WPs 3K and3M to provide propagation models (clutter loss and building entry loss) to support sharing study [4]. This paper focuses on the prediction of clutter loss (which consists of additional losses due to ground objects, besides the ground itself) in terrestrial-satellite coexistence scenarios [5]. Clutter loss is one of the main impairments for a terrestrial communication system in urban and suburban environments, especially at low elevation angles, due to the shadowing effects induced by buildings and trees surrounding the base station. On the other hand, clutter loss can also represent an advantage in the case of interference between terrestrial and satellite systems operating in the same frequency band. Clutter loss in urban and suburban environments has been significantly investigated in the past, but the scarcity of available measurements has prevented a comprehensive testing activity. Some models have been developed empirically by fitting the data collected in specific scenarios: the Hata model [6], developed on the basis of [PERSON]'s inputs, is an example of this modeling approach [7]. Another example is provided by the prediction method adopted in Recommendation ITU-R P.2108 [8]. Empirically based models typically require simple and easily accessible inputs, at the expense of limited accuracy and applicability. On the contrary, other semideterministic models, founded on physical principles, usually provide more accurate predictions. This is the case of the Walfisch and Bertoni model [9], which assumes that the propagation over buildings can be modeled as a sequence of diffractions over half-space screens, ended by a final diffraction at the last roof edge. A succession of multiple random scatterers was proposed by [PERSON] [10] to quantify the propagation loss, while different physical optics techniques were exploited by [PERSON] [5], which also consider the terrain effect. A more detailed procedure to calculate the clutter loss along the Earth satellite path is described in Report ITU-R P.2402 [11]. This paper presents a new model based on the ITU-R method [11], but with some differences to broaden its applicability and possibly enhance its accuracy for U6G systems.