Integrating Terrestrial and Satellite Multibeam Systems Toward 6G: Techniques and Challenges for Interference Mitigation

The integration of terrestrial and satellite multibeam systems has been regarded as a potential scheme for future communication networks aiming at high-rate, wide-coverage, and low-latency services. Relying on its ubiquitous coverage, integrated terrestrial and satellite multibeam systems (ITSMSs) will play a crucial role in the forthcoming 6G to increase coverage in unserved areas and support more mobile traffic in hotspots. However, the additional multibeam transmissions in an integrated system would introduce an increase of multidimensional interference, which turns the traditional noise-limited scenario into an interference-limited case. In this article, we investigate interference mitigation technologies in ITSMS toward the future 6G wireless communication scenario, where some practical applications and potential specifics are considered. Bearing this in mind, we provide an overview on current mitigation technologies with respect to three types of interference, namely inter-beam interference, intra-beam interference, and inter-system interference. We also discuss two coordinated beamforming transmission schemes to further mitigate the aforementioned three types of interference and increase the minimal user rate. Future challenges and directions for interference mitigation in the ITSMS toward 6G are also discussed.