## 6 Simulation Setup and Results
### Summary of Results and Main Findings  
A summary of the KPIs measured through this simulation study is presented in Figures 13 and 14 for baseline and DSS techniques. For completeness, we also present results for the three channels uplink use case. Red numbers in the tables indicate unsatisfactory results. For the satellite links, the main focus was to benefit from opportunistic spectrum sharing with primary terrestrial links while not introducing harmful interference to the primary links, maximize uptime, and increase spectrum utilization by using collaborative and dynamic spectrum sharing techniques. As can be seen from the averaged results,  
Figure 12: SINR graphs in the uplink use case (DSS1+). (**a**) GSO-SAT 4. (**b**) NGSO-SAT 5. (**c**) NGSO-SAT 6. (**d**) FWA 8. (**e**) FWA 10.  
avoiding interference may come at the cost of a short downtime (or reduced uptime) and a small packet loss during downtime. The key results and findings for the two use cases are summarized below:  
* Opportunistic sharing of satellite and terrestrial systems in the downlink Ka-band:
* All DSS techniques offer significant advantages over the baseline in terms of link stability and uptime. All interference events can be detected by monitoring link statistics at the receiver. The overall uptime is increased from around 82.2% for the baseline scenario to 98.6-99.5% when DSS is applied. * All DSS techniques are able to quickly recover from interference generated by known satellite and terrestrial systems. When an interference event occurs, only a few packets are lost, and any event is resolved quickly by restoring a stable connection within a few seconds in the worst case. * Terrestrial MW FWA links do not suffer from interference by satellite links. * Opportunistic sharing of satellite and terrestrial systems in uplink Ka-band:
* All DSS techniques offer significant advantages over the baseline in terms of link stability and uptime. The overall uptime is increased from around 75.4% for the baseline to 98% when DSS is applied. 98% uptime can only be achieved when:
* ACI is taken into account, in particular when high transmission power is involved, such as an uplink transmission by the GSO-ESIM. Additionally, side-lobe emissions can create interference events and should not be ignored. * Terrestrial MW FWA receivers send alert messages via the CP to warn satellite systems causing interference and to request them to move out of time-frequency slots also used by terrestrial FWA links. Some additional key findings, independent of the use cases, are:
* Besides the capability of mitigating interference events, an additional advantage of using an MF-TDMA MAC scheme combined with proposed DSS techniques is  
Figure 14: KPIs for the uplink use case, 3 channels. Figure 13: KPIs for the uplink use case, 5 channels. the increased spectrum efficiency as the DSS techniques can instantaneously adjust the allocated spectrum to match the incoming application layer load, ensuring that no more than needed spectrum is used at any given time. It can be seen that in both downlink and uplink use cases, applying DSS techniques leads to an increase in spectrum utilization from 88% to 96%. We anticipate that the proposed DSS techniques would lead to much higher spectrum utilization gains in more complex and larger-scale satellite-terrestrial deployments. * The wireless control overhead of all DSS techniques is negligible. The control overhead is only a few kB of data being exchanged per interference event between the related communicating entities, and remains constant per interference event, not scaling up with a number of deployed satellites, but with the limited number of satellites/ESIMs affecting or getting affected per interference event. * In terms of implementation, DSS1 is the simplest technique, but it can only mitigate known interference sources (advertised by CP messages), whereas DSS2 with its spectrum monitoring capabilities can mitigate unknown as well as known interference.