## 3 Simulation Parameters and Scenarios  
In 2021, 3 GPP unveiled Technical Report TR 38.821. This report provides a methodology and includes example parameters that enable the simulation of satellite-based non-terrestrial networks (NTN) offering 5G services. Its primary goal is to delineate the essential features and adaptations needed for the New Radio (NR) protocol to operate effectively within non-terrestrial networks, with a particular emphasis on satellite access [9]. Following the finalization of Release 17, several new frequency bands were introduced for the NTN segment of NR technologies. Notably, the n255 band encompasses a pair of frequency bands, 1626.5-1660.5 MHz (Earth-to-space) and 1525-1559 MHz (space-to-Earth), and the band 256, which comprises a pair of frequency bands: 1980-2010 MHz (Earth-to-space) and 2170-2200 MHz (space-to-Earth). In August 2022, SpaceX and T-Mobile unveiled a groundbreaking partnership, with plans to offer direct-to-device (D2D) services in the United States, even in the most remote and previously unreachable areas, where traditional cellular signals struggle to reach. The concept revolves around creating a novel network that harnesses the capabilities of Starlink satellites and T-Mobile's mid-band 5G spectrum. Subsequently, it was announced that Starlink's second-generation system would provide D2D services within the Frequency Division Duplex (FDD) pair of the n25 band, specifically within the 1910-1915 MHz (Earth-to-space) and 1990-1995 MHz (space-to-Earth) bands. Starlink has further extended its global reach by partnering with cellular providers, including Rogers in Canada, Optus in Australia, One NZ in New Zealand, KDDI in Japan, and Salt in Switzerland. It is important to note that if both bands are utilized for D2D services, the NTN satellite receivers of different Mobile Network Operators (MNOs) will be susceptible to interference from Starlink satellite transmitters. Since space-to-space interference scenarios have low attenuation of the interference signals, it is difficult to mitigate such interferences, especially taking into account that the victim receiver satellite will have in its line-of-sight range a very large number of satellites that will serve different countries, which means that it would be very difficult to manage such interference. Figure 1 illustrates the interference scenario between a typical NTN system operating in the n256 band and Starlink Generation 2, which operates in the n25 band. The simulation characteristics of the NTN satellite can be derived from the ITU-R Report M.2514 [10] and Technical Report 3 GPP TR 38.821. The spacecraft is located in low-Earth orbit (LEO). These parameters can be applied to both terrestrial and satellite spectrums for the S-band. The NTN system characteristics that were simulated in the study are presented in in Table 1.  
The NTN satellite employs a multibeam antenna system for both reception and transmission. This advanced antenna comprises 19 individual beams, each designed to operate within distinct frequency ranges. This particular antenna configuration is comprehensively described in the 3 GPP TR 38.821 document. Figure 2 illustrates the spatial layout of these beams on the NTN satellite's onboard antenna. In our analysis, we've considered the utilization of a typical unmodified handset (smartphone) as a reference device. Table 2 provides an overview of the smartphone's typical characteristics.