## 1 Introduction  
In the present day, the spectrum usage of satellite communications (SATCOM) is tightly regulated (mainly based on planned spatial and frequency separation), leading to static and fixed spectrum allocation. Such an approach works well, as long as the number of satellite operators and satellites is limited, and the bandwidth requirements of the services are not too high. However, the number of satellites that will be launched in the next few years is expected to grow rapidly, from projects such as Starlink, oneWeb, etc. For instance, SpaceX as of 24 October 2020 has launched 895 Starlink satellites. Furthermore, they plan to launch nearly 12,000 satellites with a possible extension to 42,000 satellites [1]. Considering the increasing satellite density, the static and fixed spectrum allocation model is not sustainable and will lead to a shortage of spectrum. Fixed spectrum assignment will eventually yield poor performance either due to interference or poor spectrum utilization. Equivalent power flux density (EPFD) rules [2] for interference management in SATCOM are still working fine for low-density scenarios. However, these rules are only designed for protecting static geostationary (GSO) satellites from interference generated by non-geostationary (NGSO) satellites or other GSO satellites. In addition, these rulesare very conservative as they apply a big protection margin that seriously limits the accommodation of new NGSO satellites. To overcome this, it becomes imperative to reuse and share the spectrum by moving towards spectrum sensing and dynamic spectrum sharing (DSS) for improving spectrum utilization and mitigating the impact of interference in high-density SATCOM scenarios. In SATCOM, traditionally, fixed satellite services (FSS) use C and K bands whereas mobile satellites use L and S bands. Due to the limited availability of L and S bands and the continuously increasing demands of broadband services via mobile satellites, Ku and Ka bands have also been assigned to mobile satellite services. Interference management is a challenging task in satellite systems in which two kinds of satellites, i.e., GSO and NGSO operate in overlapping coverage areas in the same frequency bands [3]. This situation becomes much more complicated due to many systems with thousands of such satellites all sharing the same frequency bands. Additionally, the complexity of interference management is significantly increased if satellites communicate with mobile earth stations in motion (ESIMs). There has been tremendous pressure on satellite bands due to the launch of new terrestrial services including mobile telephony, WiMAX, 5G, etc. Uplink Ka-band is one of the main target bands for the mmWave (FR2) operation of the 5G New Radio (NR) specification. Both Korea in June 2018 and United States in January 2019 concluded spectrum auctions on uplink Ka-band for terrestrial 5G services [4]. This introduction of terrestrial services in bands used by satellite services further emphasizes the need for migration from fixed to dynamic spectrum assignment and demands coexistence not only between multiple satellites but also with terrestrial services, when operating in the same bands. There are several SATCOM scenarios that may benefit from DSS. Recently, Ka-band has been gaining interest because of the more mature and cost-effective technology, and because this part of the spectrum is still less congested than the more traditional C and Ku bands [4]. However, it is anticipated that limited resources, expanding Internet use, and increasing density of satellite deployments will complicate future Ka-band deployments [5]. The European Conference of Postal and Telecommunications Administrations (CEPT) has adopted a decision for downlink communication in Ka-band (17.7-19.7 GHz), ERC/DEC/(000)7 [6], which gives guidance on the use of this band by FSS and terrestrial networks.