## 3 Interference Scenarios and Parameters of Simulated Systems  
The satellite provides an area coverage beam called the \"footprint\", where the Earth-to-space link can originate from any location and the space-to-Earth link can likewise be received at any covered location. The uplink footprint would have contours measured in either saturation flux density (SFD) or gain-to-noise temperature ratio (G/T) [9]. Given that GSO satellites cover large areas, all base stations of 5G located inside the satellite's footprint may cause interference, given that the large areas include hundreds of thousands of base stations, aggregate interference may reach significant levels. Figure 1 shows an example of possible interference from deployed 5G networks to the satellite bent pipe communication link. In the scenario shown above it may be seen that 5G networks may cause aggregate interference to the space-borne satellite receivers, taking into account that bent pipe links use transparent transponders where one Earth station transmits a signal to the satellite receiver at one frequency, then the onboard transponder translates the received signal to the other frequency, amplifies it and sends it to the other receiving Earth station. Transparent transponders are cheaper to realize, however, the cost of link degradation, since the interference received will be also amplified and retransmitted to the receiving Earth station causing increased bit error rate levels. In a typical 6/4 GHz transponder, there is no onboard processing done, and all signal degradations and noise received from the uplink are injected into the downlink together with the wanted signal, and thus the overall performance of the system will be dependent on both links [10]. Figure 2 below shows the simplified scheme of the transponder for the 6/4 GHz band with a single conversion:  
First, the signal is received at the 6 GHz band and sent to a low noise amplifier which performs amplification of the received signal. Then the signal is down-converted to 4 GHz using a local oscillator with the 2.225 GHz frequency. After that, the intermediate frequency band pass filter (BPF) removes the undesired signals and a 4 GHz signal is sent to the pre-amplifier which consists of a traveling wave tube (TWT) and is fed to a high-power amplifier (HPA). Three carrier satellites of Yamal and Express with orbital positions of 90E, 140E, and 183E were considered in the simulations as victim receivers. Table 1 provides the characteristics of each satellite link that was used in the simulations, these characteristics were  
Figure 1: Typical scenario of aggregate interference to the bent pipe satellite link. Figure 2: Block diagram of the transponder for 6/4 GHz. derived from the Master Information Frequency Register database of the ITU Radiocommunication Bureau. The study considers worst-case scenarios. At first glance, it may be suggested that the worst case would be for the footprints closer to the equator so the distance between satellites and 5G base stations would be shorter. This would be true only for the interference source with an omnidirectional antenna, while for the interferers with directional antennas this is not the case. Given that 5G base stations use beamforming, the amount of interference contribution in the Earth-to-space scenario depends more on the elevation angles towards the GSO arc rather than the distance, the lower the elevation angles, the higher interference the satellites will receive. This is why the northern parts of the Eurasian continent are more suitable since in such a geometrical configuration there would be cases when the main lobes of the BS beams will be pointed toward the GSO arc. Figure 3 presents the footprints of each satellite, the pink contour is a Yamal 90E footprint, the blue contour is an Express 140E footprint and the yellow contour is a Yamal 183E footprint.