A proactive adaptation of coding and modulation scheme to mitigate adjacent system interference in large LEO constellations

As multiple LEO satellite constellations are deployed, the likelihood of an in-line event (ILE, or a conjunction) between the satellites of different system providers operating on the same frequency but from different constellations increases. The ILE causes heightened interference at the victim receiver. In this paper we propose three schemes for mitigating the ILE-induced interference. Our first proposal relates to the adaptive coding and modulation (ACM) through which the transmitter of the affected system can lower the modulation and coding scheme (MCS) rate to counteract the reduced signal to interference ratio (SIR). However, this conventional ACM process suffers from latency due to the round-trip time (RTT) over the LEO links. We introduce a Proactive ACM (P-ACM) scheme that detects the onset of an ILE and promptly takes corrective action without the delay of multiple RTTs. Our proposed approach is more agile in responding to the ILE, thereby mitigating the impact of the ILE in terms of spectral efficiency (SE) and the latency. Our second proposal applies the successive interference cancellation (SIC) to address the impact of the interference at the physical layer receiver. This SIC scheme is effective when it matters the most – i.e., when the interference is stronger in the received power compared to the desired signal. Finally, our third proposal introduces cooperation between the two co-channel satellite systems that can mutually interfere. We conduct an analysis of the SIR during the ILE and demonstrate the effectiveness of our proposed approaches through multiple simulation experiments.