## 2 Literature Review  
During the World Radiocommunication Conference 2023 (WRC-23), new agenda item for future conference in 2027 was opened, under this agenda item ITU-R should study possible allocations for MSS that utilizes International Mobile Telecommunication (IMT) user equipment in the terrestrial cellular frequency bands with the 694-2700 MHz range. The IMT based radio interfaces include UMTS, LTE, 5G and future generations of cellular communications. This agenda item essentially will study possibility of using unmodified handsets based on LTE, 5G and future generations within the terrestrial bands of the cellular operators. However, these studies haven't yet began and will last for the next 4 years until the WRC-27. At national level some countries have already began to update their national frequency regulations to allow satellite systems operate in the terrestrial band [2], however these updates do not eliminate some interference issues.  
Thus, presently, there is a limited body of research focusing on interference issues in satellite systems deployed in the terrestrial spectrum, especially in the context of implementing device-to-device (D2D) services. While a few studies have touched upon this subject, the depth of technical analysis remains somewhat limited. This study places emphasis on investigating interference scenarios between Non-terrestrial (NTN) satellite systems and other mobile satellite service (MSS) systems, particularly within the n255 and n256 frequency bands [1].  
In the 3 GPP TR 38.863 report, titled \"Non-Terrestrial Networks (NTN) Related RF and Co-Existence Aspects\", the primary focus revolves around frequency allocations, aligning with the ITU-R Radio Regulations (RR), and encompasses several compatibility studies [3]. One published article delves into the compatibility between satellite and terrestrial segments of 5G networks in adjacent frequency channels [4]. Another publication [5] outlines the simulation methodology for interactions between Non-Geostationary Satellite Orbit (NGSO) and Geostationary Satellite Orbit (GSO) systems. Additionally, there is work dis cussing the potential of hybrid satellite/terrestrial networks, which includes considerations for traffic sharing between terrestrial and satellite Radio Access Networks (RAN) [6].  
This research, exploring the use of 3 GPP technology for satellite communication, underscores the importance of conducting interference analyses, highlighting the risks that may arise when the same spectrum is utilized for both terrestrial and satellite systems [7]. Furthermore, Ref. [8] provides insights into potential approaches for dynamic spectrum sharing between terrestrial and non-terrestrial networks in the context of 5G services and beyond.  
In summary, while numerous papers acknowledge the challenge of interference when employing the terrestrial spectrum for satellite connectivity, most have refrained from conducting in-depth technical analyses, primarily raising awareness of the issue. Consequently, there is a need for more comprehensive studies that can offer a deeper understanding of the extent of the problem, which is important for correct decision-making processes when deploying D2D services in terrestrial bands.