Coverage and interference in co-channel spectrum sharing between terrestrial and satellite networks

The satellite access to 6G services has the ambition to literally extend the coverage of the terrestrial networks to everywhere on Earth. 3GPP communication technologies are extended from Terrestrial Networks (TNs) to Non-Terrestrial Networks (NTNs), but so far the focus has been on systems where TNs and NTNs operate in their dedicated frequency bands. Providing the services in the same frequency band in satellite and terrestrial networks increases spectrum utilization efficiency, simplifies the user equipment, and shortens the delay of spectrum availability for satellite 6G services. However, the lack of capability to adapt to the expansion of TNs and the rigid sharing arrangements have not encouraged cooperative business cases between satellite and terrestrial networks. We show how cognitive, database-driven control of earth-fixed satellite beams enables co-channel DSA of NTN and TN, in the way that NTN downlink does not decrease the TN downlink capacity. We focus on the case where TN has a priority over the satellite network. The performance of the designed system is evaluated in terms of interference, capacity, coverage and spectrum utilization efficiency for cooperative and non-cooperative sharing. In the simulated study cases, the median coverage improvement with maximum -6 dB I/N at TN user equipment is 400% compared to no sharing cases. The results confirm that the maximum I/N level can be controlled by the database system to the specified level and that the separation distance between the TN and NTN coverage areas is highly dependent on the direction of the NTN beams.